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samkent
2009-Jul-15, 02:07 PM
Here is a perfect example of huge cost savings that solids will give us over liquids. The running total for Endeavour so far is $6.5 million.

http://www.space.com/missionlaunches/090713-sts127-delay-record.html


For every one-day scrub when a shuttle mission is called off after its external tank has been loaded with fuel, NASA spends about $1.3 million, said NASA spokeswoman Candrea Thomas. Paying for the wasted liquid hydrogen and liquid oxygen propellants costs about $500,000, and $700,000 goes toward paying personnel, she said.

djellison
2009-Jul-15, 02:44 PM
Are you suggesting that all LV's should be solid only? If not, then why not?

It is very VERY rare for STS to have this many scrubs. If the whole thing were solid-fulled, there would still have been scrubs, and there would still have be incurred costs for those scrubs. The material cost of the LH2 and LO2 is frankly lost in the noise floor of the total budget for the shuttle program. I'm not sure what the cost of a scrub would be without LH2/LO2 to unload - but it would not have been ZERO as you infer. If it were Ares 1 on the pad - there would have been scrub costs as well. What's the Ares 1 upper stage using? Liquid Fuels. So significant costs would be incurred both in personnel (like Endeavor) and indeed, LOX and LH2 (like Endeavor) . I see no reason to suspect that 5 scrubs of an Ares 1 launch wouldn't cost several million dollars as well.

Given that, where is your HUGE cost saving coming from? How can you honestly claim that in a similar situation, Ares 1, for example, would be $6.5m cheaper for 5 scrubs.

The commercial launch industry is dominated by liquid fuelled vehicles (Falcon 1, 9, Soyuz, Proton, Zenit) some with strap on solids (Atlas, Delta, Ariane) Are they all doing it wrong? Are Vega, Taurus and Pegasus the only LV's in the world to be doing it right?

Per kilo to LEO - can you provide proof that solids provide 'huge cost savings'.

What do you know that Elon Musk and the Space X team don't, for example. If solids really are THE way to go and have MASSIVE savings.....why are SpaceX using liquids?

(FWIW - my prefered architecture is Direct, with SpaceX / Dragon doing ISS grunt-work. I'm not a rocket scientist, I'm not pretending to be one, but I have an opinion based on the figures and feedback regarding the various architectures.)

danscope
2009-Jul-15, 03:49 PM
I should think that although SRB's are good, convenient lift, you have to at basic know that Liquid fueled rockets are the fine tuning accelerant of choice.
It's all about control. And yes, the fuel costs are indeed lost in the noise floor.
Dan

dwnielsen
2009-Jul-15, 04:46 PM
It seems that as long as we are discussing solids and liquids, we may as well mention hybrids.

http://www.airspacemag.com/space-exploration/In_Thrust_We_Trust.html?c=y&page=3

samkent
2009-Jul-15, 04:49 PM
The fact that the upper stage(s) still use liquid doesn’t change the fact that it’s a lot of money being spent. A solid first stage would just be sitting there without any additional carrying costs.

Plus if you factor in that the SSME only provide 15% of the total thrust, the costs would be significantly higher if it were an all liquid fueled launch.

Glom
2009-Jul-15, 05:32 PM
There's one way to save money on tanking/detanking: hypergolics!

cjl
2009-Jul-15, 07:06 PM
The fact that the upper stage(s) still use liquid doesn’t change the fact that it’s a lot of money being spent. A solid first stage would just be sitting there without any additional carrying costs.

Plus if you factor in that the SSME only provide 15% of the total thrust, the costs would be significantly higher if it were an all liquid fueled launch.
The liquids may provide only 15% of the initial thrust, but they provide the vast majority of the delta-v.

djellison
2009-Jul-15, 07:32 PM
samkent - could you tackle all the questions I posed please.

joema
2009-Jul-16, 01:42 PM
Here is a perfect example of huge cost savings that solids will give us over liquids....
According to that article, the cost of wasted liquid propellents is about $500 THOUSAND per launch scrub.

By comparision, the mission cost is roughly $500 MILLION.

So the propellant cost per launch scrub is about 1/1000th of the mission cost. How would a pure solid-propellent booster be a "huge" cost savings regarding launch scrubs?

slang
2009-Jul-16, 02:10 PM
What's this $700,000 for personnel? Is this some kind of temporary employment, people who only get paid per day the Shuttle is on the pad? Work hazard bonuses?

NEOWatcher
2009-Jul-16, 02:16 PM
What's this $700,000 for personnel? Is this some kind of temporary employment, people who only get paid per day the Shuttle is on the pad? Work hazard bonuses?
As much as I think a lot of that may be budgetary and allotments, there may be some reality in there.
Since so much is done by contractors, there could be some kind of temporary employment.
And; I'm sure there might be some overtime involved.

Althoug; in the financial world. Shifting resources from one budget line to another is really a cost. Although; the reality in our world is that there is a potential savings in another area that wouldn't have that allocation. At that point, you would start to need to add the complexity of the cost of idle time across all those areas.

Fazor
2009-Jul-16, 03:28 PM
What's this $700,000 for personnel? Is this some kind of temporary employment, people who only get paid per day the Shuttle is on the pad? Work hazard bonuses?

When they found the leaks in the tank(s) (sorry, I don't follow Nasa / shuttle news that closely), someone from Nasa had made a statement that they were considering the possibility of sabotage. Not that they thought these incidents were, but it got them thinking about the "what if" scenario.

One of the reasons they said it could happen was because many people are contracted specifically for the launch. The longer 'til launch, the longer they get paid. So there would certainly be motivation there to delay said launch.

So I guess the answer to your question is yes, there's temporary employment. Maybe not so much that only get paid on launch day, but there's lots of jobs that only need filled until the rocket is launched, then there's no longer a need for those people.

joema
2009-Jul-16, 06:27 PM
What's this $700,000 for personnel?...
This does not mean there's a $700k personnel cost SOLELY for propellant-related factors.

More likely each launch scrub incurs $700k additional personnel cost for various tasks.

Glom
2009-Jul-16, 06:46 PM
This does not mean there's a $700k personnel cost SOLELY for propellant-related factors.

More likely each launch scrub incurs $700k additional personnel cost for various tasks.

Well when our chopper flight was delayed overnight and we had to be put up in Lerwick, I'm sure the hotel bill alone for the company must have approached $700k.

samkent
2009-Jul-16, 06:49 PM
Are you suggesting that all LV's should be solid only? If not, then why not?

The first stage should be.



Are they all doing it wrong?

No. But Scout was an all solid launch system from Earth to orbit. No launch delays from turbo pump sensors and such. No additional costs for de tanking fuel. They just waited for the weather to clear.


If solids really are THE way to go and have MASSIVE savings.....why are SpaceX using liquids?

It’s easier to obtain money to build something you know than something new.

djellison
2009-Jul-17, 07:09 AM
The first stage should be.

Why only the first stage. Let us consider Ares 1. It would have tanking and de tanking costs. Surely if you're so damn sure that Solids are THE way to put everything into orbit, then you should be writing to your representative demanding the swop out of the J1X with a solid fulled upper stage.

After all, tanking and detanking WILL occur with Ares 1 if it ever gets to the pad - I promise you that. It WILL occur on Ares V (Or Direct).

No proposal out there is going for just solids. So tanking and detainking WILL still occur.

So from where do you get your 'huge savings', exactly?




It’s easier to obtain money to build something you know than something new.

SpaceX didn't 'know' either. It's was a startup company. They could have done either. They didn't.

slang
2009-Jul-17, 08:00 AM
From Fox (http://www.foxnews.com/story/0,2933,533280,00.html?test=latestnews):


On these occasions NASA personnel are deployed around the world, including at various transatlantic abort sites where the shuttle might land in case of an emergency.

This presumably adds up quickly, I didn't think of the abort sites.

samkent
2009-Jul-17, 12:23 PM
Surely if you're so damn sure that Solids are THE way to put everything into orbit, then you should be writing to your representative demanding the swop out of the J1X with a solid fulled upper stage.

They still need to make substantial once in orbit.


So from where do you get your 'huge savings', exactly?

Ask any project manager and they will tell you that saving millions of dollars is a huge savings. Plus look at the scale back of infrastructure. Check out the Taurus launch vehicle.

http://www.orbital.com/SpaceLaunch/Taurus/

From their brochure,



Incorporates all solid propulsion stages and proven technologies to meet mission requirements

And


Designed for easy transportability, rapid set-up and launch from austere launch sites

You can’t dismiss the benefits of solids. They are coming and I predict in a decade the majority of first stages will be solid.

formulaterp
2009-Jul-17, 02:33 PM
Check out the Taurus launch vehicle.

You mean this one?

http://www.orbital.com/SpaceLaunch/Taurus/taurus_history.shtml

75% success rate. Hasn't managed to successfully launch a fleck of paint into orbit in over 5 years. Hard to believe the world isn't beating a path to Orbital's door.



You can’t dismiss the benefits of solids. They are coming and I predict in a decade the majority of first stages will be solid.

Yeah I know those new-fangled Blu-Ray DVD's are all the rage, but I'm still convinced Betamax will make a comeback.

NEOWatcher
2009-Jul-17, 02:45 PM
Hasn't managed to successfully launch a fleck of paint into orbit in over 5 years...
Yeah, but one launch? That means nothing about the success rate.
You can also say that they only had 1 failure in the last half of the program's lifespan.


If solids are so bad, then why are strap-ons all solid?

formulaterp
2009-Jul-17, 03:18 PM
If solids are so bad, then why are strap-ons all solid?

First of all, no one is suggesting SRB's are bad. Secondly, not all strap-on's are solid. India's PSLV/GSLV uses liquid boosters with a solid first stage. But to suggest that in the next decade the majority of rockets in the near future will be using solid first stages seems ... unlikely.

Besides Ares, virtually every launcher in regular use and under development (Delta II, Delta IV, Atlas V, Falcon 1, Falcon 9, Soyuz, Proton, Zenit, Angara, Ariane V, Vega, Long March, GSLV Mk III) all use liquids.

The only exceptions are the current Indian rockets and converted ICBM/SLBM's like Minotaur.

NEOWatcher
2009-Jul-17, 03:32 PM
First of all, no one is suggesting SRB's are bad.
Picking one solid launch vehicle as an example of solid launch vehicles, and concentrating on it's failure rate certainly comes across as suggesting that SRBs are bad.
Granted, it may be the the closest example of where were heading, but how many have attempted it? And; why have they not attempted it?


Secondly, not all strap-on's are solid. India's PSLV/GSLV uses liquid boosters with a solid first stage.
Ok; "all" was said of ignorance of India's booster, but there is a solid history of solid strap-ons.

But to suggest that in the next decade the majority of rockets in the near future will be using solid first stages seems ... unlikely.
But that doesn't imply better or worse. It could just mean that the history of knowledge and experience outweighs the unknown challenges of development.


Besides Ares, virtually every launcher in regular use and under development (Delta II, Delta IV, Atlas V, Falcon 1, Falcon 9, Soyuz, Proton, Zenit, Angara, Ariane V, Vega, Long March, GSLV Mk III) all use liquids.
How many of those are from the ground up new designs, and how many of those are adaptations of earlier technologies?

djellison
2009-Jul-17, 05:15 PM
saving millions of dollars

You are yet to make a case that Ares 1 would be 'millions' better off.

Glom
2009-Jul-17, 05:19 PM
The weird thing is that solid rockets came first, ie fireworks. Was the venturing to liquid rockets and technological dead end?

samkent
2009-Jul-17, 06:38 PM
You are yet to make a case that Ares 1 would be 'millions' better off.

Just how much is NASA going to spend studying the reason for this latest foam shedding incident? I’ll bet it will be millions by itself. Add to it the huge amount of cost for the fuel loss for the tanking/detanking. Never mind the labor costs. The millions are adding up.


Hard to believe the world isn't beating a path to Orbital's door.

Old habits die hard. Should we keep the internal combustion engine just because we know how to make it work the way we want?

That’s not what NASA is all about. NASA is about new ways and new ideas. Maybe you were happy with the Gemini/Atlas combo?

Glom
2009-Jul-17, 06:41 PM
Just how much is NASA going to spend studying the reason for this latest foam shedding incident? I’ll bet it will be millions by itself. Add to it the huge amount of cost for the fuel loss for the tanking/detanking. Never mind the labor costs. The millions are adding up.


But that isn't an issue for Constellation which is of more conventional configuration.

RGClark
2009-Jul-17, 10:17 PM
Just saw this discussed on another forum:

July 17, 2009.
USAF: Orion Crew Will Not Survive Early Mission Abort.
http://www.nasawatch.com/archives/2009/07/usaf_orion_crew.html

USAF 45th Space Wing Study: Capsule~100%-Fratricide Environments (Implications for NASA's Ares-1 and Crew)
STATUS REPORT
Date Released: Thursday, July 16, 2009
http://www.spaceref.com/news/viewsr.html?pid=31792


Bob Clark

djellison
2009-Jul-17, 10:32 PM
Just how much is NASA going to spend studying the reason for this latest foam shedding incident?

That is specific to the Shuttle. That is not a problem specific to liquid fueled rockets. Direct, for example, would not have that problem.

Again - please show evidence that Ares 1 would be $6.5M better off after 5 scrubs.

NeuronExMachina
2009-Jul-17, 10:46 PM
Just saw this discussed on another forum:

July 17, 2009.
USAF: Orion Crew Will Not Survive Early Mission Abort.
http://www.nasawatch.com/archives/2009/07/usaf_orion_crew.html

USAF 45th Space Wing Study: Capsule~100%-Fratricide Environments (Implications for NASA's Ares-1 and Crew)
STATUS REPORT
Date Released: Thursday, July 16, 2009
http://www.spaceref.com/news/viewsr.html?pid=31792

Thanks for posting this... I was actually about to post it myself. I think that's pretty much the final blow to the Ares I. For those who didn't read the links, the Air Force concluded that, based on studying the failure of a similar rocket, the cloud of flaming solid propellant debris from an early abort (up to 60 seconds) of the Ares I would envelop the capsule all the way down to the ground, melting the launch escape parachutes with ~100% chance of killing the crew.

GeorgeLeRoyTirebiter
2009-Jul-18, 06:24 AM
Ok; "all" was said of ignorance of India's booster, but there is a solid history of solid strap-ons.

Sure, but R-7 derivatives with liquid-fueled strap-on boosters have been in service continuously for the past fifty years (Soyuz). The Long March 2 and 3 can use liquid strap-ons. Some variants of the Ariane 4 also used liquid-fueled boosters, or a mix of liquid and solid. While most strap-ons have been solid, liquid boosters aren't unheard of.


Besides Ares, virtually every launcher in regular use and under development (Delta II, Delta IV, Atlas V, Falcon 1, Falcon 9, Soyuz, Proton, Zenit, Angara, Ariane V, Vega, Long March, GSLV Mk III) all use liquids.

Um...unless ELV has made some drastic changes in the past couple of years, the first three stages of Vega will be solid. I'll point out that it's not a large launcher—it's projected to have less performance than the smallest Delta II in ULA's catalog. Arianespace intends to use it to cover the small satellite market, with Soyuz in the middle and Ariane 5 for heavy-lift and GTO.


How many of those are from the ground up new designs, and how many of those are adaptations of earlier technologies?

That depends on how you define it. In the broadest sense, every launch vehicle is based on earlier technologies.

More specifically, what changes are necessary for a launcher or stage to be considered "new"? The Delta II is considered to be a descendant of the Thor IRBM, but it's like the old joke about Washington's hatchet. There's been so many improvements and upgrades that it's now a very different rocket.

galacsi
2009-Jul-18, 07:48 AM
Solid rockets are not very performing in term of ISP (http://en.wikipedia.org/wiki/Specific_impulse) or speed of the ejected gases.

So an all solid rocket will need 3 or 4 stages when an all liquid rocket need only 2 or 3.

But solid rocket can be made very powerful , with a big thrust and it is very useful at the beginning of the flight , to go through the low atmosphere and to accelerate the faster as possible.Because if you accelerate very slowly you waste your thrust just doing a little more than compensating for gravity.

These are the reasons they are used as strapon or as the first stage.

Also even if they are less performing they are cheaper and simpler to operate.

djellison
2009-Jul-18, 08:57 AM
After 50 years of LV development - it's quiet clear that Solids have their place - thrust augmentation for 60-120s early in flight or the launch of small payloads via Vega, Pegasus, or Taurus.

Samkent clearly has an agenda which he is not being entirely clear about - and is, sadly, misrepresenting the facts to push this agenda.

Larry Jacks
2009-Jul-18, 03:41 PM
Solids are pretty reliable but when they do fail, they fail spectacularly. So much so, the Air Force has assessed that if Ares I (http://www.nasawatch.com/archives/2009/07/usaf_orion_crew.html) failed early in the flight, the crew will be killed. They based this study on the failure of a Titan IV SRB back in 1998. The analysis result is that the Orion launch escape system wouldn't be able to get the crew clear of the raining debris. Nylon parachutes don't like raining debris. Here's a video of a Delta II failure (http://www.youtube.com/watch?v=WsVzpE7ltb8) caused by an solid that exploded. Such failures are rare but they do happen from time to time.

Several things can cause a large solid rocket motor to fail. Two of the more common failure causes are insulation separation and propellant cracks. Insulation separation allows the hot combustion gases to come in contact with the casing wall. This can cause more propellant to ignite prematurely. Propellant cracks cause more propellant surface area than intended to be exposed for combustion, resulting in higher pressure inside the casing. In either case, the resulting explosion is usually spectacular.

RGClark
2009-Jul-18, 06:14 PM
Solids are pretty reliable but when they do fail, they fail spectacularly. So much so, the Air Force has assessed that if Ares I (http://www.nasawatch.com/archives/2009/07/usaf_orion_crew.html) failed early in the flight, the crew will be killed. They based this study on the failure of a Titan IV SRB back in 1998. The analysis result is that the Orion launch escape system wouldn't be able to get the crew clear of the raining debris. Nylon parachutes don't like raining debris. Here's a video of a Delta II failure (http://www.youtube.com/watch?v=WsVzpE7ltb8) caused by an solid that exploded. Such failures are rare but they do happen from time to time.
.

The debris field from that Delta II explosion is pretty extensive with large, flaming chunks flying long distances.

Bob Clark

joema
2009-Jul-18, 11:41 PM
...Air Force has assessed that if Ares I failed early in the flight, the crew will be killed...
It's true the study said the Orion capsule wouldn't survive a launch abort attempt from T+30 to T+60 sec.

However, the study apparently assumed intentional self-destruct of the SRB, and escape system firing roughly coincident with that.

In the real world, that's not how it would work.

For a manned launcher, the SRB would be heavily instrumented with vital parameters tied into the escape system. An incipient catastrophic failure would trigger the launch escape system before that failure actually happened. This was done on each manned launcher before the shuttle.

You don't wait until something blows up to eject. Humans are too slow. Certain critical parameters will instantly trigger an abort, before the failure cascade destroys the vehicle.

In the Titan IV failure, there were several seconds BETWEEN the vehicle anomaly and BEFORE the destruct charges were fired. In a manned launcher those seconds would be used to get the crew to safety via the launch escape system.

GeorgeLeRoyTirebiter
2009-Jul-19, 04:40 AM
Would a motor case failure (as occurred with a Titan IV motor during a 1991 static test, a Titan IV launch in 1993, and the 1997 Delta II launch that Larry Jacks linked to) give sufficient warning to trigger the LES beforehand? Unlike "burn-through" failures, case ruptures are usually sudden.

Dave J
2009-Jul-19, 06:17 AM
Thanks for posting this... I was actually about to post it myself. I think that's pretty much the final blow to the Ares I. For those who didn't read the links, the Air Force concluded that, based on studying the failure of a similar rocket, the cloud of flaming solid propellant debris from an early abort (up to 60 seconds) of the Ares I would envelop the capsule all the way down to the ground, melting the launch escape parachutes with ~100% chance of killing the crew.

Would this not apply to any configuration using large RSRMs as well? (i.e. Direct)?
Note that the Titan was destroyed by the RSO, who hit the button and blew the (non-man rated) solids as well as the core. The Titan solids also have significantly thinner walls than the RSRMs.
I don't know what studies have been done on the various potential RSRM failure modes, but STS51L showed one, and the SRB survived that accident until blown by the RSO. Barring a major undetected structural flaw, it would "seem" the thick walled RSRMs are much less likely to present situations where the case "ruptures" (as in the Delta SRM failure, and the RSO destruct of the Titan).
I'm of the Story Musgrave thought on the big solids...they scare me. But they do have an amazing history of reliability, with the one major Shuttle exception. This case would not, it appears, be an automatic "100% fratricide" situation in an Aires 1 application.
BTW, how have all the seals been performing since the major post-51L redesign?
Just some thoughts at this end...

Dave J
2009-Jul-19, 06:24 AM
Would a motor case failure (as occurred with a Titan IV motor during a 1991 static test, a Titan IV launch in 1993, and the 1997 Delta II launch that Larry Jacks linked to) give sufficient warning to trigger the LES beforehand? Unlike "burn-through" failures, case ruptures are usually sudden.

In the early ATK brochures, there was some sort of engineering analysis diagrams of SRB failures, and they "obviously" pointed towards a "sufficient warning" story...whether this was accurate, or just marketing, I couldn't guess.
I'm curious as to how far, in various flight regimes, the LES would carry Orion from the failing booster before drogue chute deployment?

joema
2009-Jul-19, 01:30 PM
Would a motor case failure (as occurred with a Titan IV motor during a 1991 static test, a Titan IV launch in 1993, and the 1997 Delta II launch that Larry Jacks linked to) give sufficient warning to trigger the LES beforehand? Unlike "burn-through" failures, case ruptures are usually sudden.
It would depend on where the event happened, altitude and velocity -- all of which impact airflow over the ejected material.

There are various SRB failure modes, all of which more likely than a case burst: loss of thrust vector control, burn-through of O-ring, igniter failure, etc.

Out of about 250 SRBs flown in the shuttle program, there has never been a case burst. The O-ring failure on Challenger was a progressive event that a launch escape system could have detected.

In general I believe ATK analysis pessimistically assumes an Ares I case burst would not be suvivable. However this category of failure represents only a small subset of all possible SRB and vehicle failure modes.

In reality there are probably survivable case burst events, depending on the exact circumstances, e.g, location on booster, size, altitude, velocity, launch escape performance, etc.

The SRBs on unmanned boosters are manufactured and tested to lower standards than the shuttle SRBs. Each shuttle SRB is X-rayed and ultrasonically tested hundreds of times. Also each shuttle SRB is designed and manufacturered with a 200% structural safety margin, far more than unmanned vehicles.

NEOWatcher
2009-Jul-20, 02:49 PM
While most strap-ons have been solid, liquid boosters aren't unheard of.
Thanks; more for me to look at.
But; besides my lack of fluency in boosters, I am trying to get across the idea that quantity of one or the other is not an indicator that it is better or worse.
There may be some correlation, but the design of the entire flight parameters seems to be a larger consideration.



That depends on how you define it. In the broadest sense, every launch vehicle is based on earlier technologies.
(re: new design)
Yes; absolutely. I have no clue where to draw the line myself, but there are some that are much more obvious than others.

danscope
2009-Jul-20, 05:32 PM
yes.... that would be control.

GeorgeLeRoyTirebiter
2009-Jul-20, 10:53 PM
But; besides my lack of fluency in boosters, I am trying to get across the idea that quantity of one or the other is not an indicator that it is better or worse.
There may be some correlation, but the design of the entire flight parameters seems to be a larger consideration.

Yeah, I was just being pedantic. I'm sure someone could devote an entire book to the engineering trade-offs involved in deciding between liquid and solid engines; neither is clearly superior.


I have no clue where to draw the line myself, but there are some that are much more obvious than others.

I thought about going through formulaterp's list of launchers and marking them as "new" or "derived", but I realized that the dividing line would be arbitrary and I'd need a paragraph of text to explain each one.


While reading about large solids, I found something unexpected. A 1965 NASA study looked at replacing the first stage of the Saturn IB with a monster 260 inch (6.6m) diameter monolithic solid motor. Aerojet got as far as test-firing three motors before the funding ran out—another victim of end-of-Apollo cutbacks. So, the arrangement of a solid first stage and cryogenic second stage to put a capsule into LEO isn't so new after all.

cjameshuff
2009-Jul-22, 12:20 AM
Aside from the fact that the fuel costs are still quite tiny in comparison to the overall launch costs, meaning there isn't much to save by optimizing that portion of the costs...not all liquid rockets are equal. The Shuttle uses liquid hydrogen. Aside from being notoriously prone to leaking given the slightest excuse, the low density thus requires a huge tank with a large surface area, and liquid hydrogen is both deeply cryogenic and has a low heat of vaporization, boiling at 20K with only 0.9 kJ/mol compared to the 90K and and 6.8 kJ/mol of liquid oxygen. This adds up to large losses of the relatively expensive LH2.

A LOX/RP1 engine doesn't have this problem. RP1 doesn't boil away in the tank, and LOX is very cheap, the costs of dealing with it are mostly in the equipment and preparation. The LOX/RP1 combination is better suited for higher thrust first stages than LOX/LH2, making solid boosters unnecessary, and though it has lower specific impulse, it is far better in that respect than solids. The higher density also means a far smaller fuel tank, reducing the size of the first stage. The higher Isp of hydrogen is of more benefit on higher stages, which coincidentally also tend to be far smaller, reducing the boiloff problem...or hydrogen can be eliminated completely.

We went to the moon taking this approach, and the Saturn V still seems like a far better balanced vehicle than many of the vehicles which followed it, which seemed to have a confused obsession with both high performance and difficult to use LH2 and dangerous and low performance solid rockets.
http://commons.wikimedia.org/wiki/File:Saturn_v_schematic.jpg

But again...fuel costs are a tiny portion of the total costs. It's a few million dollars in this case, yes, but it's only a few million. There's far, far more money to be saved by looking elsewhere.

ugordan
2009-Jul-24, 08:57 PM
Regarding the recent USAF study, there's a major point I didn't see made here.
When a LAS on Ares I is triggered and before SRB destruct at the time point this study talks about (IIRC between 30 s and 60 s into the flight), the dynamic pressure on the Orion/LAS stack is immense. This is an inherent "feature" of the Ares I design (one that actually drived the already oversized LAS for Ares I) and other shuttle-derived approaches don't suffer as much.

The end effect of it is that even though the LAS motor is firing, it's not actually putting much distance between Orion and the failing booster - the dynamic pressure drag just negates all that escape rocket impulse. At the other end you've got this high thrust booster thing potentially chasing you. You need it to terminate thrust and stop chasing you ASAP.

There is talk here about how SRBs are safe and fail very rarely, but the point is it doesn't have to be an explosive SRB failure to result in this scenario at all. It can be any other reason for abort during that time period - a guidance failure (like the Titan IV, Ariane V), SRB thrust vector control failure, upper stage structural collapse due to loss of pressurization, etc. Even though these aren't immediately catastrophic SRB failure modes, the way the SRB termination system works effectively makes no difference. The SRB blows up raining a hail of flaming chunks, regardless of whether the casing ruptured by itself or was ripped apart deliberately.

Also bear in mind the range safety requirement is that a failing booster needs to be destroyed as early as possible in order to prevent the possibility of FTS getting disabled by ongoing booster breakup/failure, resulting in no way of disposing of a tumbling booster which can potentially harm the innocent public. All the more since the timeline we're talking here is still early flight, SRB close to the pad and still loaded with propellant.

Rhaedas
2009-Jul-24, 09:10 PM
Just to throw something else in the mix, Fraser just posted today an article on a biofueled LOX rocket test.

http://www.bautforum.com/universe-today-story-comments/91177-company-flies-biofuel-rocket-video.html

Along with the whole "green" aspect, the article claims that the JP-8 mix outperformed a similar RP-1 rocket, and ran cleaner.

Damburger
2009-Jul-24, 09:26 PM
The costs of delaying a shuttle launch do not show the advantages of solids, but the disadvantage of cryogenic liquid fuels. If you were to find the costs to delaying, say, a Proton launch - they would be a lot less, even taking into account the smaller payload.

Cryogenics are a major pain in the arse to use; but they have a clear advantage over solids and other liquid fuels in terms of Isp. It is popular to pretend the Shuttle is just a big pile of rubbish engineering decisions, but using liquid hydrogen is not one of them. The combination of high thrust/low Isp solids for boosters and lower thrust/high Isp for the main stage is a sound method for building rockets, which is why the European Ariane 5 uses the same approach despite being designed independently.

In any case, solids have a big set of problems that any liquids do not have:

1. Not practically throttlable.
2. As mentioned by myself and others, not great Isp
3. Worse vibration problems that liquid engines, which has caused difficulties with Ares I

And there are problem more I can't of right now. Rocket scientists are not fools; if solids were so universally better nobody would bother spending the huge amounts of money required to develop and fly liquid engines.

joema
2009-Jul-24, 09:55 PM
...There is talk here about how SRBs are safe and fail very rarely, but the point is it doesn't have to be an explosive SRB failure to result in this scenario at all. It can be any other reason for abort during that time period - a guidance failure (like the Titan IV, Ariane V), SRB thrust vector control failure, upper stage structural collapse due to loss of pressurization, etc. Even though these aren't immediately catastrophic SRB failure modes, the way the SRB termination system works effectively makes no difference. The SRB blows up raining a hail of flaming chunks, regardless of whether the casing ruptured by itself or was ripped apart deliberately....Also bear in mind the range safety requirement is that a failing booster needs to be destroyed as early as possible in order to prevent the possibility of FTS getting disabled by ongoing booster breakup/failure.
Those are good points. Any major failure in any system during powered SRB ascent will generally necessitate firing the FTS charges on the SRB. Even if the SRB itself was infinitely reliable, there would still be valid scenarios where other systems fail and the SRB must be destroyed.

The disagreement is between the USAF and NASA models for that case. Namely, NASA says there would be adequate separation between the capsule and the detonated SRB, where the Air Force says no.

Also it's not totally clear to me the FTS must be fired immediately after LAS activation. In the Challenger situation, the RSO waited 37 sec before firing the FTS on the SRBs. Admittedly that was somewhat further downrange and SRB propellant was mostly expended, so potential risk to public was less.

However the Challenger situation would seem to indicate the FTS system is robust and reliable.

ugordan
2009-Jul-25, 12:16 AM
Also it's not totally clear to me the FTS must be fired immediately after LAS activation.
Consider that it could be a no-win situation either way.

* If the SRB is destroyed immediately after abort, you don't have to worry about the booster chasing you, but you have a bunch of flaming propellant fragments engulfing you after you deploy parachutes. IIUC, the assumption in the study is the propellant fragments have a similar drag coefficient as Orion so they will feel similar aerodynamic effects. End result: because of high dynamic pressure you didn't get far away from the debris.

* If the SRB isn't destroyed immediately, because the SRB+US stack has so much more mass per surface area, it doesn't feel the aerodynamic drag as much of an issue, while your light Orion capsule struggles with its LAS to get away. So you could (depending on the breaks and how much the booster tumbles and in what direction) have the booster chase you quite closely. Then after a delayed destruct you again end up in a debris field.

This is just one of the side-effects of baselining a shuttle booster for something it was never intended to do - be the sole first stage of a launch vehicle. All its shortcomings have come up - the thrust oscillation problem, the controllability issue and now this. SRBs were logically designed to provide as much of a kick early in the flight for the shuttle and when you translate that to the Ares I design, it means higher maximum dynamic pressures than any other launch vehicle, liquid or SDLV. Which is a nightmare for LAS design.

Glom
2009-Jul-28, 08:47 PM
1. Not practically throttlable.

They can be throttled, but I believe that's done by the packing of the solid propellent, which means that they can only fly a predetermined profile, not ones that can be controlled in flight.

Damburger
2009-Jul-29, 09:08 AM
They can be throttled, but I believe that's done by the packing of the solid propellent, which means that they can only fly a predetermined profile, not ones that can be controlled in flight.

Yes, of course, what I meant was you can't actively control the throttle. Its determined when the propellant is manufactured.

joema
2009-Jul-29, 11:30 AM
Yes, of course, what I meant was you can't actively control the throttle. Its determined when the propellant is manufactured.
Which is exactly like ALL liquid booster engines except the space shuttle SSME. With that one exception, liquid engines also cannot be throttled.

In fact, solids are relatively easy to manufacture with a fixed throttle schedule. E.g, the shuttle SRBs vary thrust by nearly 2:1 over the flight period. They throttle back during max Q, then throttle up afterwards. By contrast, most liquid engines have fixed thrust determined by design and manufacture.

djellison
2009-Jul-29, 11:58 AM
With that one exception, liquid engines also cannot be throttled..

That is very wrong.

As I understand, both EELV variants throttle, as do some other liquid fuelled LV's.

Damburger
2009-Jul-29, 12:40 PM
Which is exactly like ALL liquid booster engines except the space shuttle SSME. With that one exception, liquid engines also cannot be throttled.

The RS-68 can also be throttled. As can the Soviet/Russian NK-33. And the RD-170. But don't let yourself be troubled by facts.


In fact, solids are relatively easy to manufacture with a fixed throttle schedule. E.g, the shuttle SRBs vary thrust by nearly 2:1 over the flight period. They throttle back during max Q, then throttle up afterwards. By contrast, most liquid engines have fixed thrust determined by design and manufacture.

So, like I just said, SRBs can't be throttled actively. SSME's, as well as those engines I mentioned, and certainly more engines that I couldn't quickly confirm as throttlable - can be throttled actively.

Solids have no control over the thrust or duration of burn once they are lit. This means you can forget about engine-out capability, and you can also forget about accurate burns of any kind. Solids belong on the sides of a big liquid fueled rocket during the first couple of minutes of launch. You can't build an entire space program on them.

NEOWatcher
2009-Jul-29, 12:56 PM
So, like I just said, SRBs can't be throttled actively.
True, but how often is that capability needed outside of the normal flight profile reasons for it?

Solids have no control over the thrust or duration of burn once they are lit. This means you can forget about engine-out capability
On a single engine machine, I think you can forget about engine out capability completely anyway.

, and you can also forget about accurate burns of any kind.
Why? And to what degree?

samkent
2009-Jul-29, 01:35 PM
You can't build an entire space program on them.

Isn't that exactly what NASA is doing? Are you saying NASA with it's big computers and big budget is wrong and it won't work???

Glom
2009-Jul-29, 01:59 PM
The LM DPS could be throttled.

djellison
2009-Jul-29, 02:23 PM
True, but how often is that capability needed outside of the normal flight profile reasons for it?

Every flight profile would require a different solid fuel grain mix. If you tweaked the payload much, it's be a new requirement, a new thrust profile, a new grain mix and thus a new qualification program.

Make the booster only part of the thrust profile and you can compensate with the liquids and you have much more flexibility.


And yes, Samkent, imho, Ares 1 is wrong. Part of NASA has got this wrong. I believe Space X, LoMart, Boeing, Ariane, Starsem, Energia, the Direct team etc etc..... I don't believe the Constellation program has it right. I think they have it wrong. I'm not alone.

NEOWatcher
2009-Jul-29, 02:35 PM
Every flight profile would require a different solid fuel grain mix. If you tweaked the payload much, it's be a new requirement, a new thrust profile, a new grain mix and thus a new qualification program.
I can see your point, but I really don't see this happening with Ares I. It is a very specific use booster with a very specific payload.
I'm not sure what kind of load variances there would be, but I would think that if the variance was so much to change the burn profile, that they might rethink the payload.


I don't believe the Constellation program has it right. I think they have it wrong. I'm not alone.
I realize you are replying to Samkent, but I wanted to comment.
I personally am not sure that they got it right, but I do feel that they got it close enough to right that there might be factors that I don't understand that bring it into right.
I will wait and see, I will be satisfied with a performance on par with the Russians, but that's going to take some time. Otherwise, I really don't see an apples to apples comparison with cargo.

djellison
2009-Jul-29, 03:01 PM
It is a very specific use booster with a very specific payload. .

The Orion will evolve. We have a 4 seat version for ISS. Hopefully they'll restore a 7 seat version for ISS. Then there's the Lunar version, or beyond E-M system missions. There are launches to ISS. There are launches for Earth-Orbit-Rendezvous. Something like the Shuttle must surely adjust its launch profile for different ISS missions, I'd wager Saturn V adjusted its thrust profile from Apollo 8 to Apollo 17.

Margin margin margin. That's what a chap is saying to the Aug. Comm. right now. Ares 1 doesn't have any.

Damburger
2009-Jul-29, 03:25 PM
Isn't that exactly what NASA is doing? Are you saying NASA with it's big computers and big budget is wrong and it won't work???

No. NASA is not building an all-solid orbital launcher.

NEOWatcher
2009-Jul-29, 04:33 PM
The Orion will evolve. We have a 4 seat version for ISS. Hopefully they'll restore a 7 seat version for ISS.I thought the 4 seater was only a block I version to be superseded by the block II (or whatever they are called). In other words, one configuration at a time.

Then there's the Lunar version, or beyond E-M system missions.
I don't think they are planning the Ares I to do much more than head to LEO to rendezvous with an Ares V payload to go further.


Something like the Shuttle must surely adjust its launch profile for different ISS missions...
Sure, but will it be that drastic that they can't compensate?


...I'd wager Saturn V adjusted its thrust profile from Apollo 8 to Apollo 17.
I would call that irrelevent because that's way outside the scope of Ares I.


Margin margin margin. That's what a chap is saying to the Aug. Comm. right now. Ares 1 doesn't have any.
Yes; I can agree with that. But the issue that I am having with the whole thing is seperating the fact that this is limited to Ares I design, or an overall issue with trying to design or modify a human rated booster.

samkent
2009-Jul-29, 04:37 PM
Margin margin margin. That's what a chap is saying to the Aug. Comm. right now. Ares 1 doesn't have any.

Doesn’t the margin come from the second stage? The heavier the payload the longer/stronger the second stage burns.


I will wait and see, I will be satisfied with a performance on par with the Russians,

I assume you mean Soyuz. Even at its weakest, Ares is bigger, heavier, and more capable than Soyuz.

NEOWatcher
2009-Jul-29, 04:40 PM
Doesn’t the margin come from the second stage? The heavier the payload the longer/stronger the second stage burns.
I wasn't going to bring that up, but I wonder that myself.


I assume you mean Soyuz. Even at its weakest, Ares is bigger, heavier, and more capable than Soyuz.
So; I guess that should satisfy me...

ugordan
2009-Jul-29, 04:56 PM
I wasn't going to bring that up, but I wonder that myself.
In Ares I case, yes, the upper stage is forced to do most of the heavy lifting on account of the first stage being anemic. Which doesn't mean you can just shove a heavier upper stage and payload on top of the first stage. At 1st stage burnout you would wind up at a lower velocity, necessitating the US not only to pick up that difference, but also do more heavy work itself because of a heavier payload.

Here's the problem : when your staging velocity is low and upper stage initial thrust-to-weight ratio low, you suffer increased gravity losses which hurt your overall performance. This is one of the reasons the current Ares I stack pretty much hit a brick wall performance-wise.

Both EELV types actually suffer from this, but they were never designed for primarily LEO missions, but GEO missions where the low initial T/W ratio is offset by lower stage weight (one RL-10 engine only), and actually why a Falcon 9 could theoretically compete with their LEO performance even using a lower energy US. Adding a 2nd engine to the EELV US dramatically boosts their LEO performance (Atlas used to offer dual-engine Centaurs regularly and could redevelop them for A-V).

A 2nd J-2X engine is a NO-GO for Ares I because they decided so (reliability considerations - fewer engines, fewer failures, yada yada yada) and it would be overkill for the relatively light stage anyway.

Antice
2009-Jul-29, 05:58 PM
basically what it boils down to is that a clean sheet design would have been better than any of the alternatives.

samkent
2009-Jul-29, 06:24 PM
(reliability considerations - fewer engines, fewer failures, yada yada yada)

Funny how the term 'reliability considerations' keeps popping up with liquids.

Out of the 254 SRBs used in the US manned program…

Zero launch delays due to a SRB problem.
Zero failures to ignite when commanded.
Zero in flight shut downs.
Zero SRB explosions.

On the other hand, the liquid side of the equation has caused more launch delays than I can count. Even the first launch after Columbia was delayed for two weeks due to fuel sensor problems.

Larry Jacks
2009-Jul-29, 06:27 PM
basically what it boils down to is that a clean sheet design would have been better than any of the alternatives.

Sometimes, trying to save time and money by using existing hardware ends up costing far more and taking longer.

When the Ares I was first proposed, it was going to use an existing 4 segment SRB with the upper stage powered by a SSME. It was supposed to cost $14 billion to develop. Unfortunately, SSME's were designed to be started on the ground with lots of supporting equipment. It wasn't feasible to launch it in flight. So, they changed to an upgraded version of the venerable J-2 engine. However, that wasn't powerful enough so they added a 5th segment to the SRB and reportedly had to adjust other design factors. Then came serious concerns about vibration levels high enough to threaten the crew and upper stage survival, increasing Orion capsule weight and decreasing Ares I lift capacity. And the cost is now reported to be $35 billion with more delay.

There is debate as to whether a Delta IV Heavy or Atlas V variant could do the job. Personally, I believe it could. I'm also hoping SpaceX is successful with their Falcon 9/Dragon. Putting all of our eggs in a single basket leaves us vulnerable to extended downtime in the event of an accident (over 2 years each following the Challenger and Columbia accidents).

ugordan
2009-Jul-29, 06:38 PM
Funny how the term 'reliability considerations' keeps popping up with liquids.
/cut

On the other hand, the liquid side of the equation has caused more launch delays than I can count. Even the first launch after Columbia was delayed for two weeks due to fuel sensor problems.

Then again, every time a U.S. manned flight liquid engine had (or "had" in the case of one STS flight) a problem in flight and shut down, the vehicle moved on to carry the crew to orbit. I don't have to tell you what happened the last time a SRB had a problem, not that that particular problem wouldn't have been survivable on a vehicle with a LAS, but nonetheless.

ugordan
2009-Jul-29, 06:51 PM
There is debate as to whether a Delta IV Heavy or Atlas V variant could do the job. Personally, I believe it could.

D-IVH might be able to do just fine even now, yet there's an ongoing program, on track that will put out RS-68A with better performance which most definitely could do anything Ares I was supposed to do. I believe the uprated Delta will be available in 2010/2011.

Atlas V heavy would blow both Delta IV and Ares I out of the water w/respect to LEO performance. It's very much not a paper rocket and basically ULA is waiting for someone to place an order for them to finish up the last bits of design work and deliver a flight unit 30 months later. I actually prefer it to the D-IVH, but one thing politicians apparently don't like about it is the Russian booster engine. Funny, actually, when you consider that same engine boosts a good deal of the country's top national security assets for the NRO office.

Both of them have the advantage (IMHO) of not having any solid boosters on, both are already flying (A-VH effectively, 95% hardware already flies on A-V vanilla) and have flight history. Ares I only has statistics and promises based on flight history of the shuttle booster, yet the Ares I SRB is a new development. Just like you cannot make predictions on J-2X reliability based on J-2 history, neither can 4seg and 5seg SRBs be directly comparable.

But we know powerpoint rockets are always better than real, flying hardware. :rolleyes:

samkent
2009-Jul-29, 07:13 PM
But we know powerpoint rockets are always better than real, flying hardware.

Cheaper too.

Larry Jacks
2009-Jul-29, 07:57 PM
As spectacular as an Atlas V Heavy would be, it might be severe overkill to carry an Orion capsule and service module to LEO. One of the other Atlas V variants might be able to do the job. This would require using solid fueled strap-ons but the industry has a lot of experience with that as opposed to using one giant solid fuel rocket for the first stage of a heavy lifter.

ugordan
2009-Jul-29, 08:05 PM
It wouldn't be overkill, IIRC it would have 25+ tons to LEO, a healthy margin for Orion growth during its development. You might be thinking about proposed later Phase I/II, etc incarnations, I'm talking about the Atlas equivalent of the Delta IV Heavy 3-core configuration.

GeorgeLeRoyTirebiter
2009-Jul-29, 09:09 PM
The Atlas V 500 series can only lift 10 to 20 tonnes to LEO, depending on the number of solid boosters, so it's not quite enough to launch Orion. The base Atlas V HLV is expected to be able to put over 29 tonnes to LEO.

joema
2009-Jul-29, 09:35 PM
Then again, every time a U.S. manned flight liquid engine had (or "had" in the case of one STS flight) a problem in flight and shut down, the vehicle moved on to carry the crew to orbit. I don't have to tell you what happened the last time a SRB had a problem...
However in that case (STS-51F abort to orbit, 1985), a spurious shutdown of a liquid-fueled engine nearly doomed the crew.

Nothing was wrong with the engine -- it shut down due to a sensor failure. A 2nd engine almost shut down, also cause by a sensor problem. At that point Challenger was beyond RTLS (return to launch site), but didn't have sufficient energy for a TAL (trans-atlantic) abort. It would have ditched in the ocean, which was non-survivable.

Fortunately after the 1st failure, redline limits were inhibited on the engines, which prevented that. However that removes all automated engine health monitoring, essentially running them in "open loop" until they blow up. So after one failure, the ability to automatically shut down the liquid engines was nullified.

While ability to shut down a liquid engine is often viewed as purely advantageous over solids, STS-51F shows this introduces the possibility of spurious shutdowns which can be potentially fatal. Also STS-51F is not the only case of a booster having spurious engine shutdowns.

Likewise on STS-93, two SSME engine controllers failed due to a short circuit, which fortunately were on two different engines. At that point only a backup controller kept each engine running. Had those failed, it would have caused a single-engine RTLS abort, which might not be survivable.

Both STS-51F and STS-93 problems could not happen with a solid propellant booster. Personally I'd rather fly on a liquid-fueled booster, but the above shows it's not that black and white.

Larry Jacks
2009-Jul-29, 09:52 PM
Nothing about booster design is as simple as black and white. It's said that an airplane is a series of compromises flying in close formation. That's equally true for boosters.

In all the years of rocketry and spaceflight, no one has tried to build a substancial booster (payload more than a few thousand pounds) using only solid rocket motors. Solids have proven very good in combination with liquid fuel engines for first stages. There are sound engineering reasons why this is true. If the reports I've read are true, the Ares I design is proving the case yet again that solids aren't as suitable for being the sole power for a major first stage.

ugordan
2009-Jul-29, 09:56 PM
Personally I'd rather fly on a liquid-fueled booster, but the above shows it's not that black and white.
Right, and if the examples above show anything, it's that a crew launch vehicle needs to have viable abort modes at all times during ascent, i.e. no black zones. Shuttle has significant times in ascent where an abort is a really hairy proposition for the crew. (I'd personally rather have false positive detections than undetected valid triggers for immediate abort).

And we're back to square one again, the problems of making such an abort system work with a solid booster.

Glom
2009-Jul-29, 10:37 PM
Zero in flight shut downs.


For a solid rocket, that's not much of an achievement.

djellison
2009-Aug-02, 09:24 AM
Funny how the term 'reliability considerations' keeps popping up with liquids.

Out of the 254 SRBs used in the US manned program…

Zero launch delays due to a SRB problem.


An internal valve problem with the hydraulic steering system on the left-hand solid rocket booster of space shuttle Discovery is being analyzed in the Vehicle Assembly Building, NASA said this evening.
Any work to replace hardware associated with the hydraulic power unit would take place after Discovery is rolled out to the launch pad, an agency spokesman said. What, if any, impact this issue could have on the targeted August 25 launch date is not yet known.

"During pre-rollout preparations and testing Saturday morning in Kennedy's Vehicle Assembly Building, a valve failed inside Discovery's left-hand solid rocket booster hydraulic power unit tilt system, which helps steer the SRB during launch," the spokesman said in a statement.

The spokesman indicated that the delay in Discovery's move to the pad from Monday to Tuesday was caused by the ongoing evaluations of the valve problem.

I've not even gone looking for SRB's causing delays. This was just there this morning. Thought I'd put it out there. You're being dishonest claiming that SRB's never cause delays.

Oh - and we've had TWO inflight shutdowns of SRB's. Just after the Challenger explosion - remember - the one caused by an SRB.

RGClark
2009-Aug-02, 03:14 PM
Any chance of replacing the Ares I solids with the old Saturn F-1 engines?
This Astronautix page gives the F-1 a vacuum thrust of 1,740,134 lbf at a weight of only 18,498 lb for a thrust to weight ratio of nearly 100 to 1.
The Astronautix page on the Ares I solids give it vacuum thrust of 3,480,122 lbf but an empty weight of 221,230 lb (!) for a thrust to weight ratio of only 16 to 1 (!)
The tank mass for a kerosene-LOX engine is only about 1/100th that of the propellant mass. So even if you used the same propellant mass as the Ares I solids of about 1,400,000 lb that would only add 14,000 lb to the lower stage empty mass. But actually the propellant mass would probably be less since the F-1 had a better Isp at 304 s compared to 265 s for the Ares I solids.
Given this, how much larger payload could we launch to LEO using the 2 F-1 engines in place of the Ares I solids as the 1st stage?
How much could we launch to LEO using just 1 F-1 engine as the 1st stage?


Bob Clark

ugordan
2009-Aug-02, 03:22 PM
Any chance of replacing the Ares I solids with the old Saturn F-1 engines?
Technically, F-1(A) production could be restarted, but it would cost over $500 million in current dollars, would take time and probably in the end wouldn't be cost-effective. ATK lobbyists spread out everywhere wouldn't like it very much, either.

More on the subject in this article (http://www.thespacereview.com/article/588/1).

DrRocket
2009-Aug-02, 05:52 PM
Thanks for posting this... I was actually about to post it myself. I think that's pretty much the final blow to the Ares I. For those who didn't read the links, the Air Force concluded that, based on studying the failure of a similar rocket, the cloud of flaming solid propellant debris from an early abort (up to 60 seconds) of the Ares I would envelop the capsule all the way down to the ground, melting the launch escape parachutes with ~100% chance of killing the crew.

That is just plain silly.

It is a "no brainer" to conclude that if there is an inhibitor failure (the cause of the Titan IV A accident used in the model) that there will be little chance of escape. In fact, that sort of failure will happen too quickly to be detected and effective abort action to be taken.

However, that hardly precludes a successful abort and escape triggered by the detection of other failure modes.

If you think you are going to escape with high probability from any sort of explosive failure mode, whether involving liquid or solid rocket motors, you are kidding yourself. These things typically happen really fast. I have seen quite a few and the reaction time is at best a couple of milliseconds. When you watch high speed films, all of the action takes place in 1-2 frames even at rates of 1000 frames/sec.

The other item that applies is that even in an explosion like the one in the study, the propellant debris is not uniformly distribute, so nothing is "enveloped". Yes, there can be a lot of chunks of burning propellant in the air. But they are also spread out, and do not "envelop" in the sense of a cloud of hot gas. It is closer to a shotgun pattern with a very open choke. So, a parachuting capsule might encounter disaster from a large chunk of burning propellant, or it might get away relatively unscathed. In either case it is less vulnerable that it would be if it were still attached to the ruptured rocket motor case. The hard part would be to get far enough away prior to the actual case rupture so as to survive the shock waves in the first place.

The analysis presented appears to come from branches of the Air Force that do not regularly deal with solid rockets.

ugordan
2009-Aug-02, 06:29 PM
That is just plain silly.

It is a "no brainer" to conclude that if there is an inhibitor failure (the cause of the Titan IV A accident used in the model) that there will be little chance of escape.

The accident used as the model is the 1998 Titan IV A-20 flight which suffered a guidance failure due to electrical shorts. Erroneous pitch-down command was given at around 40s after a computer reset that exposed the vehicle to very high aerodynamic stresses, the failure from then on pretty much mimicked the inaugural Ariane V. Shortly after, the stack began to fall apart and the vehicle's Inadvertent Separation Destruct System destroyed two perfectly good SRBs. It was not an SRB failure, nor was it instantaneous.

The point of the study was that high aerodynamic loads imparted by Ares I prevent Orion and its LAS from getting far enough away even in this case when there are a few seconds of warning time.



The analysis presented appears to come from branches of the Air Force that do not regularly deal with solid rockets.
Maybe so, but Air Force is still responsible for that big red button and USAF probably don't like the prospect that destroying a SRB after an abort would fry the crew alive. Death from firendly fire. RSO is responsible for public safety, but a proposition like this would present a moral dilemma to him.

DrRocket
2009-Aug-02, 07:07 PM
The accident used as the model is the 1998 Titan IV A-20 flight which suffered a guidance failure due to electrical shorts. Erroneous pitch-down command was given at around 40s after a computer reset that exposed the vehicle to very high aerodynamic stresses, the failure from then on pretty much mimicked the inaugural Ariane V. Shortly after, the stack began to fall apart and the vehicle's Inadvertent Separation Destruct System destroyed two perfectly good SRBs. It was not an SRB failure, nor was it instantaneous.

In that case there may be enough time to get far enough away, which also calls the analysis into question. That will depend largely on the thrust from the launch escape motors. They are pretty energetic. The propellant in those things is rather hot stuff by industry standards.

BTW that analysis may well have had the failure mode that you describe, but there then another failure within a few years prior (1993?) that did result from an inhibitor problem relating to a poor repair procedure. Sorry, if I got my failures mixed up -- faulty memory.



Maybe so, but Air Force is still responsible for that big red button and USAF probably don't like the prospect that destroying a SRB after an abort would fry the crew alive. Death from firendly fire. RSO is responsible for public safety, but a proposition like this would present a moral dilemma to him.

I appreciate the work of range safety. They have a tough job. But they have that same tough job and moral delimma right now with the STS. The only thing missing is the escape mechanism.

I have strong personal doubts that any launch abort system will work effectively. Rocket failures just don't often give much notice. But I am also convinced that such a system will do no harm, and might work in some situations.

I have enough experience to be quite confident that a prediction of certain failure is no more credible than a prediction of certain success.

ugordan
2009-Aug-02, 07:21 PM
In that case there may be enough time to get far enough away, which also calls the analysis into question. That will depend largely on the thrust from the launch escape motors.

The problem is the very high max-Q environment basically negates (and this was apparently confirmed by slightly better models) any thrust Ares I LAS can provide. Hard to imagine, but Ares I does have the highest max-Q environment I know of for a manned booster. In fact, other SDLV vehicles would probably solve the problem by a larger LAS on account of their greater performance (and lower max-Q!), but in the case of Ares I, the LAS is already oversized and no more mass margin exists.

Conflicting requirements:
* need to destroy SRB early so it doesn't chase you (doesn't feel that max-Q as much as small capsule), a rough model by a member on another forum suggested aborted Ares I stack would pass by the Orion ~5 seconds after abort
* need to wait as long as possible so you clear the SRB debris field afterwards



BTW that analysis may well have had the failure mode that you describe, but there then another failure within a few years prior (1993?) that did result from an inhibitor problem relating to a poor repair procedure. Sorry, if I got my failures mixed up -- faulty memory.
Yep, and that one was also a Titan IV.

DrRocket
2009-Aug-02, 07:24 PM
Yep, and that one was also a Titan IV.

Titan IV A specifically. There is a big difference in the solids between the IV A and the IV B.

DrRocket
2009-Aug-02, 07:38 PM
The problem is the very high max-Q environment basically negates (and this was apparently confirmed by slightly better models) any thrust Ares I LAS can provide. Hard to imagine, but Ares I does have the highest max-Q environment I know of for a manned booster. In fact, other SDLV vehicles would probably solve the problem by a larger LAS on account of their greater performance (and lower max-Q!), but in the case of Ares I, the LAS is already oversized and no more mass margin exists.

Conflicting requirements:
* need to destroy SRB early so it doesn't chase you (doesn't feel that max-Q as much as small capsule), a rough model by a member on another forum suggested aborted Ares I stack would pass by the Orion ~5 seconds after abort
* need to wait as long as possible so you clear the SRB debris field afterwards

.

If the dynamic pressure completely countereacts the thrust from the LAS then you are hosed. But if not one ought to be able to get away by applying thrust transverse to the trajectory, to escape laterally. You would then have to wait for the solids to pass by before deploying the parachute, but that would seem to be a good strategy in any case. 5 seconds strikes me as a long time for this to happen, particularly under max Q conditions.

In the life of a solid rocket failure 5 seconds is usually indistinguishable from 2 weeks. Which simply supports the notion that the escape and abort is not going to handle most SRB failure modes, but might handle other types of failures.

But only might. In reality we have zero experience with any sort of in-flight safe abort of a space launch. Rockets are, because of high performance requirements (gravity is a bear) inherently a set of single-point failure modes. Riding rockets is inherently dangerous. You do everything possible to assure success, but these things are not Greyhound busses.

The LAS is at least as much public relations as it is rocket science. But it is better than nothing.

Antice
2009-Aug-02, 08:21 PM
any escape system that has been thought trough applies transverse forces to escape the vehicle. just like the catapult seat in a jet fighter that rights itself up to avoid smashing the pilot into the ground during a low altitude inverted ejection.
The LES does not have to outpace the first stage for more than half a second or so. once the capsule is gone on it's way, the rocket is no longer an aerodynamic vehicle and what happens with it is anybody's guess.

Delaying the self destruct by 5 seconds wont affect range safety by much at that altitude. Even if you apply range violation immediate destruct options, that is just a chance one has to take. range violation may or may not happen depending on the chain of events that lead to the abort scenario.

samkent
2009-Aug-02, 08:50 PM
Like I mentioned in another thread: What if they detonate just the joints of the segments? That would stop any additional forward thrust and keep the propellant contained.

Antice
2009-Aug-02, 09:00 PM
someone claimed internal pressure would rip the segments apart if you did that.
I cant see why that would happen actually since the segments themselves arent being ripped apart when the pressure is at max during normal operation.
popping the segments from the bottom and up by starting with dumping the throat of the rocket would relieve the pressure a great deal by itself.

ugordan
2009-Aug-02, 09:11 PM
I cant see why that would happen actually since the segments themselves arent being ripped apart when the pressure is at max during normal operation.

The same way shuttle casings dont rip open during normal operation - they are designed to withstand the maximum operating pressure and then some. Just like the joints. If you ripped all the segments open, the initial pressure burst would probably give the same result - violent propellant dispersion similar to a FTS charge longitudinal detonation.

Probably a better way would be to sever the SRB nozzle first, let the pressure inside drop and then just rip the casing apart, any old way. The problem is it's not so simple to drop the nozzle without risking it jamming the throat and blowing everything up again. IIRC the way the nozzle is nested inside the SRM makes this difficult.

DrRocket
2009-Aug-02, 09:28 PM
Like I mentioned in another thread: What if they detonate just the joints of the segments? That would stop any additional forward thrust and keep the propellant contained.

The shuttle uses a longitudinal cut implemented by means of a shaped charge. That is pretty standard for solids with large length/diameter ratios. The purpose is to render then non-propulsional very quickly.

A cut along the joint would result in an initial HUGE forward thrust increase, quickly going to zero.

DrRocket
2009-Aug-02, 09:32 PM
someone claimed internal pressure would rip the segments apart if you did that.
I cant see why that would happen actually since the segments themselves arent being ripped apart when the pressure is at max during normal operation.
popping the segments from the bottom and up by starting with dumping the throat of the rocket would relieve the pressure a great deal by itself.

Openinn up the joint would cause the cases to be "ripped apart". But it is not the best means of thrust termination either.

Max Q is irrelevant. Rocket motor case design is driven by internal pressure. That pressure dwarfs external dynamic pressure, but it also puts the cases in a state driven by hoop tension. Compressive loads are a different kettle of fish.

The Q load is primarily axial in any case and is not a structural problem at all.

DrRocket
2009-Aug-02, 09:40 PM
The same way shuttle casings dont rip open during normal operation - they are designed to withstand the maximum operating pressure and then some. Just like the joints. If you ripped all the segments open, the initial pressure burst would probably give the same result - violent propellant dispersion similar to a FTS charge longitudinal detonation.

Probably a better way would be to sever the SRB nozzle first, let the pressure inside drop and then just rip the casing apart, any old way. The problem is it's not so simple to drop the nozzle without risking it jamming the throat and blowing everything up again. IIRC the way the nozzle is nested inside the SRM makes this difficult.

Severing the nozzle give the same problem as severing the joints -- a HUGE initial thrust increase. It is not nearly as effective as a longitudinal cut, for large length/diameter motors because it does not open up enough flow area and it opens it up in the wrong place. It would be more effective to sever the forward dome, and that is done on some motors with a lower l/d ratio.

The throat is part of the nozzle, so severing the nozzle would not jamm up the throat. It would be equivalent to suddenly enlarging the throat.

The SRM nozzle is a conventional submerged nozzle design. If you wanted to jetison the nozzle it would be pretty simple to do with a shaped charge mounted so as to cut the aft dome or the stationary shell of the flexseal. But that is not a good design from the perspective of thrust termination.

The proven technique for motors in this class is a long axial cut. That is also the means used to dispose of motors in this size class when necessary (Although for shuttle motors they are actually washed out so as to recover the steel cases.)

RGClark
2009-Aug-02, 10:47 PM
Forgot to give the links for the Astronautix pages on Ares and the F-1:

Ares.
http://www.astronautix.com/lvs/ares.htm

F-1.
http://www.astronautix.com/engines/f1.htm


Bob Clark

GeorgeLeRoyTirebiter
2009-Aug-03, 04:23 AM
Any chance of replacing the Ares I solids with the old Saturn F-1 engines?

Heck, if you're going to do that, skip the trouble of restarting F-1 production and just use an RD-171 or a pair of RD-180s. If Russian suppliers are a problem, P&W Rocketdyne has a license to build the RD-180 (although they have yet to do so). Of course, they are Not Invented Here, so I really don't expect they'd be used for the Constellation program (it's also another strike against a possible human-rated Atlas V).

RGClark
2009-Aug-03, 01:31 PM
Heck, if you're going to do that, skip the trouble of restarting F-1 production and just use an RD-171 or a pair of RD-180s. If Russian suppliers are a problem, P&W Rocketdyne has a license to build the RD-180 (although they have yet to do so). Of course, they are Not Invented Here, so I really don't expect they'd be used for the Constellation program (it's also another strike against a possible human-rated Atlas V).

Thanks for that. Here's the Astronautix pages on the RD-171 and RD-180:

RD-171
http://www.astronautix.com/engines/rd171.htm

RD-180
http://www.astronautix.com/engines/rd180.htm

You would need 2 to 3 of these to match the thrust of the Ares I first stage solids. But the thrust to weight is so much better you might be able to match the payload to orbit just using one of these engines. (You would have 200,000 lbs less dry mass at launch.)


Bob Clark

Larry Jacks
2009-Aug-03, 04:03 PM
I met a Lockheed representative at a space conference about 10 years ago who claimed the RD-180 was the best rocket engine anywhere. The engine is respected in the community. Since it's derived from the RD-170 family, I suspect that engine is also held in good regard even though it was "not invented here." A good engine is a good engine.

ugordan
2009-Aug-03, 04:23 PM
Performance wise, I think RD-180 is actually a step up from its RD-170 ancestor, i.e. it's not simply half the engine with a weaker turbopump. I agree, both are remarkable engines. What the Russians lacked in large combustion chamber expertize (see F-1 and its own combustion stability problems), they made up in metallurgy.

My favorite Orion to LEO launch vehicle choice would be an Atlas V HLV. RP-1 is perfectly suited for a first stage propellant. Its energy density is much higher than LH2 (compare Delta and Atlas 1st stage tankage), ultimately leading to cheaper handling and operation. A subtle side-effect of higher LH2 Isp means you also need more total delta-V from a LH2 first stage because you suffer greater gravity losses. There's not an engine out there that gives you more bang per kg of RP-1 than RD-170/180. The Russians also recently unveiled plans to develop basically their own counterpart to the A-V HLV, for the same purpose of launching a human capsule into orbit. I'm not sure how serious they are about it, but that's a confirmation enough that Atlas V is a well thought-out vehicle. And just imagine the performance of 3 CCBs if you could crossfeed the propellants...

DrRocket
2009-Aug-03, 07:28 PM
A subtle side-effect of higher LH2 Isp means you also need more total delta-V from a LH2 first stage because you suffer greater gravity losses.

A not-so-subtle side effectd of LH2 is that you have lousy density, so the inert weight fraction goes up and you need more performance to compensate.

RGClark
2009-Aug-05, 06:15 PM
Thanks for that. Here's the Astronautix pages on the RD-171 and RD-180:

RD-171
http://www.astronautix.com/engines/rd171.htm

RD-180
http://www.astronautix.com/engines/rd180.htm

You would need 2 to 3 of these to match the thrust of the Ares I first stage solids. But the thrust to weight is so much better you might be able to match the payload to orbit just using one of these engines. (You would have 200,000 lbs less dry mass at launch.)


This page gives altitude and velocity of the Ares I at first stage separation as 59 km and 2024 m/s:

Space Launch Report - Ares I.
http://www.spacelaunchreport.com/ares1.html

Then we can estimate how much fuel it would take to reach this delta-v, including the gravity drag for that altitude, based on the Isp of the liquid fuel engines and the mass of
the Ares upper stage.

A preliminary calculation shows the RD-180 wouldn't have enough thrust for the fuel load required. However, the RD-171 should be able to do it using the specifications given here:

RD-171
http://www.astronautix.com/engines/rd171.htm

The second stage of the Ares I is about 175,000 kg, when you include payload. The RD-171 weighs 9,500 kg. Even if you used as much fuel mass as the SRB of 1,400,000 lb, a tankage mass ratio of 1/100th the propellant mass for kerosene/LOX engines would only add 7,000 kg. So call the the upper stage plus the empty weight of the lower stage 200,000 kg.
You want to reach the same velocity of 2,000 m/s and altitude of 50 km reached by the SRB. The delta-v required for the altitude can be found from the equation v^2 = 2gh. So for h = 50,000 m, v = 990 m/s.
Air drag losses it turns out are relatively small for large cylindrical rockets that get rapidly out of the atmosphere, about 150 m/s for medium sized launchers by this page:

Flight Mechanics of Manned Sub-Orbital Reusable Launch Vehicles with Recommendations for Launch and Recovery.
http://www.spacefuture.com/archive/flight_mechanics_of_manned_suborbital_reusable_lau nch_vehicles_with_recommendations_for_launch_and_r ecovery.shtml

So let's call the total delta-v 3,000 m/s. The Isp of the RD-171 is given on the Astronautix page as 309 s at sea level and 337 s in vacuum. Let's give it an average Isp of 320 s. Then the mass ratio is exp(3,000/3200) = 2.554. So for a mass at first stage burnout of 200,000 kg, the mass at launch would be 2.554x200,000 = 510718 kg. Of this 510,718-200,000 kg = 310,718 kg would be fuel, less than half of the fuel load of the SRB for Ares I.
The launch mass of 510,718 kg = 1,123,580 lb is well within the thrust capabilities of the RD-171 to lift, with its sea level thrust of 1,697,300 lb.


Bob Clark

GeorgeLeRoyTirebiter
2009-Aug-05, 06:57 PM
A preliminary calculation shows the RD-180 wouldn't have enough thrust for the fuel load required.

That's why I suggested using a pair of RD-180s. Two of 'em together have almost 1300kg more mass than an RD-171, but that's more than offset by the 106kN increase in liftoff thrust (and almost four times that at altitude) and the slight improvement in Isp.

RGClark
2009-Aug-05, 07:23 PM
RD-180 would be able to do it using two engines, while being able to launch larger payloads. There has been some trouble getting the RD-180 man rated since its original developement was in Russia.
A planned reusable, American engine rather comparable to the RD-180 also could accomplish it using 2 engines, the RS-84:

RS-84
http://www.astronautix.com/engines/rs84.htm

The RS-84 was cancelled however, perhaps because its capabilities were so similar to the RD-180 or perhaps because it was felt unnecessary with SRB's on the Ares.


Bob Clark

Larry Jacks
2009-Aug-05, 08:01 PM
The term "man rated" means whatever NASA wants it to mean. When comparing their paper rocket (Ares I) to the EELVs, NASA said it would be too difficult to make the EELVs as safe. When the engineers point out problems with the Ares I design, the requirements for man-rating slip. Back in 2006, Lockheed and Bigelow signed an agreement (http://www.nasaspaceflight.com/2006/09/lockheed-and-bigelow-human-rated-eelv-deal/) to work on launching humans on the Atlas V.

The reason for the NASA ESAS man-rating concerns was due to the 25mT CEV mass requirement, which ESAS maintained could not safely even be met by the massive Atlas V Heavy variant. According to a Lockheed Martin paper unveiled this week at the Space 2006 conference, the basic Atlas V 401 can meet FAA and NASA man-rating requirements with little modification with a much smaller capsule mass of 20,000 lbs.

At 20,000 lbs, there is enough margin in the Atlas V 401’s flight envelope to allow the crew to safely abort at any time during launch, closing all unsafe ‘black-zones’. Also, at 20,000 lbs structural loads on the vehicle are decreased enough so that a detailed Lockheed analysis indicates that all primary structures meet NASA 1.4 Factor of Safety margins.

Analysis also shows the Russian-built RD-180 engine in this regime revealed only one component that fell a hair below the 1.4 margin, at a 1.38 Factor of Safety.

Antice
2009-Aug-05, 08:18 PM
going with a smaller Orion would mean cutting back on capabilities even more.
Esas recommended a 25mT CEV in order to get all the functionality they wanted. however it seems like 25mT was too low as well going by how many desired functions have been scaled back or eliminated from the design. like the ability to land the capsule on land.

Larry Jacks
2009-Aug-05, 09:24 PM
NASA has already given up on having Orion land on land. They've also cut back the number of passengers to the ISS. All of this is because the weight keeps going up in part due to Ares I design decisions. For example, due to the projected vibrations from the SRB, they've had to add a lot of weight for a dampening system that wouldn't be required with a liquid first stage. They've also had to reinforce other structural components for the same reason. I've also read that the launch abort system needed for the Ares I is larger than would be required for an EELV.

I saw this statement the other day and couldn't agree more: "Weight is the enemy of all things that fly." That's especially true for space systems where each additional kilogram of on-orbit mass requires several additional KGs of launch vehicle mass. Unfortunately, the mass of the Orion keeps going up while the lift capability of the Ares I keeps going down. The designs are not closing and there is no margin.

Antice
2009-Aug-05, 10:34 PM
The dampening is part of the interstage, so is not adding mass to Orion at all. it's mass that is dropped at the same time as the first stage.
Dropping it that early makes it a lot smaller penalty than what you are trying to portray here.

secondly. lets take a propper look at those numbers for atlas V 401. 20000Lbs = 9090kg. aprox = 9mT
24mT = 54800Lbs....

We are suddenly looking at a capsule the scale of SpaceX dragon here.
to be fair. the dragonLab variant just about breaches 10mT
That wont bring anyone back to the moon however.

ugordan
2009-Aug-05, 11:27 PM
We are suddenly looking at a capsule the scale of SpaceX dragon here.
to be fair. the dragonLab variant just about breaches 10mT
Noone's proposing downscaling Orion to fit on an Atlas V 402. The point is a lot of the arguments about black zones, man-rating requirements are misportrayed and unsubstantiated when it comes to EELVs.

If Atlas V 402 was deemed good enough for carrying humans in OSP, so would an Atlas V HLV (far exceeding Ares I performance) be for carrying the full-blown Orion.

The RD-180 of "questionable" quality (seeing as it's Russian and all) already employs a bunch of health monitoring sensors, which come from it's ancestor, RD-170 which was man-rated for Energia. Whatever "man-rated" really means for NASA nowadays - the requirements seem to be changing by the minute, every time Ares I falls short on one of them.

DrRocket
2009-Aug-05, 11:53 PM
Noone's proposing downscaling Orion to fit on an Atlas V 402. The point is a lot of the arguments about black zones, man-rating requirements are misportrayed and unsubstantiated when it comes to EELVs.



This statement is correct. It is also recognized by many within NASA, the ones that count.

There is essentially no difference in quality and reliability between "man-rated" systems and the systems used to launch satellites. In both cases the payloads are sufficiently important that literally everything that one knows to do to assure mission success is done. The stakes are just too high to cut corners in either case.

Antice
2009-Aug-06, 05:53 AM
While the Atlas V Heavy probably could do the job there is that pesky political problem of what to do with all those laid off when the plug is pulled on the shuttle.
I'm trying to skirt on thin ice due to politics here tho. and i dont want to spark a debate about politics. but Ares was chosen for political reasons as much as technical ones. No launcher can ever be totaly free of politics. Chosing Atlas V heavy over some other comercial launcher would spark a whole new set of opposition that would have been just as politically motivated as lots of the current opposition to Ares is.

Keep in mind that in a perfect world we could have used both the Atlas for the CEV and stil get Ares V built to do the cargo part of a lunar mission. Alas. the world is not perfect, and the time between paying for the design work for Man rated Atlas V heavy and starting on Ares V would be just as big as the time between starting on Ares I and Ares V. Layoffs are Inevitable when workers are not needed for maybe as long as 5 years or more. At least with Ares I you get to keep some of the shuttle people at their jobs for the duration.

ugordan
2009-Aug-06, 09:21 AM
Chosing Atlas V heavy over some other comercial launcher would spark a whole new set of opposition that would have been just as politically motivated as lots of the current opposition to Ares is.
Frankly, out of the three possible alternatives - Delta IV H, Ares I, Atlas V HLV (one could also add Falcon 9 Heavy if one were feeling optimistic), Atlas V variant would be by far the cheapest. IIRC, costs are proprietary for ULA vehicles, but numbers that I've seen crop up for Delta IV Heavy are around $400 million per flight, Atlas V HLV would be roughly half that and god knows how much Ares I would effectively cost. Instead of wasting all that money on reproducing capability already existing within commercial vehicles (and ones that are deemed safe enough to carry multibillion satellites and handle "nuclear" launches - NH), NASA would be better served by concentrating solely on a single heavy lifter, if anything. Otherwise the prospects of affordable and sustainable HSF flights beyond LEO are significantly diminished. Politics be damned.

djellison
2009-Aug-06, 09:35 AM
While the Atlas V Heavy probably could do the job there is that pesky political problem of what to do with all those laid off when the plug is pulled on the shuttle..

So we should intentionally choose the option that is inefficient?

How about we move those people into production, processing etc of whatever LV we do use, and any savings can be ploughed back into doing more flights?

Antice
2009-Aug-06, 10:29 AM
I dont condone taking those political factors into consideration when choosing one system over another more than you do. But that just arent the case ever. cant get away from those pesky politicians as long as we are talking government funded programs. nature of the beast and all that.
Nasa do need Ares V class launcher in one iteration or other if they want to get to the moon and build a base there.
in regards to personell transport to the ISS. a simpler LEO only capsule could be made trough the COTS program inside of a 5 year period.

Larry Jacks
2009-Aug-06, 12:47 PM
While the Atlas V Heavy probably could do the job there is that pesky political problem of what to do with all those laid off when the plug is pulled on the shuttle.
I'm trying to skirt on thin ice due to politics here tho. and i dont want to spark a debate about politics. but Ares was chosen for political reasons as much as technical ones. No launcher can ever be totaly free of politics. Chosing Atlas V heavy over some other comercial launcher would spark a whole new set of opposition that would have been just as politically motivated as lots of the current opposition to Ares is.

Thousands of people are facing layoffs when the Shuttle stops flying. That's a given. They simply won't be needed until flight operations begin again. Now, the recently released price for developing the Ares I is up to about $35 billion. Yesterday, I linked to an Aviation Week article that states the Ares/Orion may not fly until 2019, a gap of up to 9 years. $35 billion and a 9 year gap is a high price to pay for the Ares I. An EELV wouldn't take nearly so long so those people wouldn't be out of work for such an extended period.

Plus, the EELVs are built in the US (IIRC, they're built in Decatur, Alabama - just 20 miles from Marshall Space Flight Center). It's true that the RD-180 is built in Russia but Pratt & Whitney has an agreement for US production.

djellison
2009-Aug-06, 01:02 PM
Nasa do need Ares V class launcher in one iteration or other if they want to get to the moon and build a base there.

The Direct 3.0 proposal would suggest otherwise. Call it Ares IV if you like, but the behemoth 5.5 segment solids and a ground-up new fuel tank are not required.

Antice
2009-Aug-06, 01:38 PM
Could you not make a new thread in order to discuss direct instead of jacking this one with it. Weither Ares I is what it is suposed to be or not have no bearing what so ever on direct or it's feasibility what so ever.

RGClark
2009-Aug-06, 02:46 PM
The term "man rated" means whatever NASA wants it to mean. When comparing their paper rocket (Ares I) to the EELVs, NASA said it would be too difficult to make the EELVs as safe. When the engineers point out problems with the Ares I design, the requirements for man-rating slip. Back in 2006, Lockheed and Bigelow signed an agreement (http://www.nasaspaceflight.com/2006/09/lockheed-and-bigelow-human-rated-eelv-deal/) to work on launching humans on the Atlas V.

The reason for the NASA ESAS man-rating concerns was due to the 25mT CEV mass requirement, which ESAS maintained could not safely even be met by the massive Atlas V Heavy variant. According to a Lockheed Martin paper unveiled this week at the Space 2006 conference, the basic Atlas V 401 can meet FAA and NASA man-rating requirements with little modification with a much smaller capsule mass of 20,000 lbs.

At 20,000 lbs, there is enough margin in the Atlas V 401’s flight envelope to allow the crew to safely abort at any time during launch, closing all unsafe ‘black-zones’. Also, at 20,000 lbs structural loads on the vehicle are decreased enough so that a detailed Lockheed analysis indicates that all primary structures meet NASA 1.4 Factor of Safety margins.

Analysis also shows the Russian-built RD-180 engine in this regime revealed only one component that fell a hair below the 1.4 margin, at a 1.38 Factor of Safety.

The Atlas V Heavy wouldn't be able to lift the same payload as the Ares I because it uses a much smaller engine for the upper stage, the RL-10A:

RL-10.
http://www.astronautix.com/engines/rl10.htm

The J-2X engine planned for the Ares I upper stage has 10 times the thrust of the RL-10A:

J-2.
http://www.astronautix.com/engines/j2.htm

Using two RD-180's to replace the Ares I first stage, while keeping the J-2X for the upper stage, would actually allow you to increase the payload to orbit.

The same would be true of the RS-84 if development were restarted. This engine was also planned to be reusable:

July 21st, 2003
Kerosene Engine Passes Design Milestone.
Written by Fraser Cain.
http://www.universetoday.com/2003/07/21/kerosene-engine-passes-design-milestone/

This article from 2003 stated a full scale model would have been ready for testing four years after that in 2007. The program was cancelled in 2004 however. If you suppose there was an additional year of development before it were cancelled in 2004, then conceivably a full scale model could be ready for testing by 2012 if development were restarted this year.


Bob Clark

djellison
2009-Aug-06, 02:53 PM
Could you not make a new thread in order to discuss direct instead of jacking this one with it. Weither Ares I is what it is suposed to be or not have no bearing what so ever on direct or it's feasibility what so ever.

You said Atlas V is required for the Moon.

It isn't.

That's not hijacking, that's fact.

samkent
2009-Aug-06, 03:10 PM
What about construction time?

I can’t find the lead time for an SRB. At one point I did read that traditional booster ‘X’ required 18 months from signing to delivery. I don’t remember which booster it was, but I’m almost certain it wasn’t a manned booster.

From my limited viewpoint, I see production of SRB segments as much easier than the liquid counter parts. Therefore allowing the ability to slip an extra launch into the schedule if required for say emergency evacuation of an injured person on the ISS.

ugordan
2009-Aug-06, 04:30 PM
The Atlas V Heavy wouldn't be able to lift the same payload as the Ares I because it uses a much smaller engine for the upper stage, the RL-10A

I'm afraid it's not as simple as that. An A-V HLV would significantly shift the delta-V split toward the booster part, unlike Ares I which relies on the upper stage to do most of the heavy work. Atlas V first stage with 3 liquid cores would burn for an excess of 5 minutes total during which time it would accumulate more velocity than provided by Ares I 1st stage. As a result, the trajectory would be more ballistic, thus lowering the gravity loss effects of a weaker engine. Plus, they would likely fly a dual-engine Centaur anyway.

If the 5 SRB configuration of an Atlas V can boost 18 tons to LEO, I see no reason to doubt the much larger HLV variant boosting at least 25 tons. Which not only matches Ares I performance, but exceeds it. There's more to calculating launch vehicle performance than comparing engines, including stage dry masses, engine Isp and thrust, propellant loads, etc.

EDIT: In fact, I've just found the data in the Atlas V Mission Planner's Guide the LEO performance of an Atlas V HLV with a dual-engine Centaur and to an 28.5 degree inclination, 185 km circular orbit is 29.4 tons. Beat that, Ares I!

Antice
2009-Aug-06, 04:43 PM
You said Atlas V is required for the Moon.

It isn't.

That's not hijacking, that's fact.

If you actually bothered to read what i wrote you will see that i wrote Ares V class
that means whatever in the same lift capability as what is projected for Ares V.
It does not mean that any particular paper rocket is prefered at all. just that heavy lift Is needed. and the Atlas V heavy isn't true heavy lift as i see it.
there really aren't all that many rockets projects to choose from without going back to the Apollo era or a bunch of obscure paper rockets most people outside those with special interest have heard about.

Antice
2009-Aug-06, 04:49 PM
I'm afraid it's not as simple as that. An A-V HLV would significantly shift the delta-V split toward the booster part, unlike Ares I which relies on the upper stage to do most of the heavy work. Atlas V first stage with 3 liquid cores would burn for an excess of 5 minutes total during which time it would accumulate more velocity than provided by Ares I 1st stage. As a result, the trajectory would be more ballistic, thus lowering the gravity loss effects of a weaker engine. Plus, they would likely fly a dual-engine Centaur anyway.

If the 5 SRB configuration of an Atlas V can boost 18 tons to LEO, I see no reason to doubt the much larger HLV variant boosting at least 25 tons. Which not only matches Ares I performance, but exceeds it. There's more to calculating launch vehicle performance than comparing engines, including stage dry masses, engine Isp and thrust, propellant loads, etc.

EDIT: In fact, I've just found the data in the Atlas V Mission Planner's Guide the LEO performance of an Atlas V HLV with a dual-engine Centaur and to an 28.5 degree inclination, 185 km circular orbit is 29.4 tons. Beat that, Ares I!

one question. are those numbers for the depressed trajectory demanded for human space-flight or just cargo. If it's just cargo then you may need to recalculate those numbers quite a bit. it costs more delta-v to use a depressed trajectory than the more commonly used one for satellites and cargo.

ugordan
2009-Aug-06, 05:14 PM
are those numbers for the depressed trajectory demanded for human space-flight or just cargo.
A depressed trajectory is said to affect the performance of a EELV heavy with something like a 5% hit so that would work out to roughly 28 tons. If you take even a 10% hit (which I believe would not affect the dual-engine, beefed up Atlas HLV, but would be closer to the hit of a vanilla Atlas 401), that's 26.4 tons directly inserted into orbit. Ares I inserts Orion onto a suborbital trajectory (like the Shuttle at MECO), supposedly due to upper stage disposal considerations, but some people claim it's due to performance shortfalls. Not sure which is true, but it does leave Orion some 30 - 60 m/s (IIRC) short of a safe orbit which does need to be provided by the SM as effectively a small 3rd stage.

There are other considerations to this, of course - the above figure assumes a 5 meter wide, "Large" payload fairing (and that's *huge*) to the Atlas so that's a several ton hit on the unmanned Atlas, but on the other side on a manned Atlas a LAS would be needed so that more or less balances out.

Antice
2009-Aug-06, 06:02 PM
not disposing of the second stage while still marginally suborbital would be silly since we don't need any more junk up there.
30 to 40ms short is close enough that the burn needed is very small and the SM can not be counted as a third stage for the launcher. this is done for cargo that goes to leo as well. to keep the garbage amounts up there down.
it's the same reason the ET is dropped at the point it is dropped. proper garbage disposal is important after all.

Larry Jacks
2009-Aug-06, 06:29 PM
not disposing of the second stage while still marginally suborbital would be silly since we don't need any more junk up there.

Depending on the flight profile, it doesn't have to be a problem. When I was tracking Soviet space launches, they frequently placed the upper stage rocket body into orbit. Using spring loading, you can simultaneously increase the satellite payload and deboost the rocket body (action/reaction). Most of those Soviet rocket bodies decayed within a few days.

30 to 40ms short is close enough that the burn needed is very small

The amound of propellant needed to boost a 25 mT object can be fairly substancial, depending in part to the Isp of the propellants used. Playing with this delta-v calculator (http://www.strout.net/info/science/delta-v/intro.html), if the loaded mass is 25,000 KG and the Isp is 320 seconds (about right for a hypergolic SM), then it takes 3000 KG of propellant to add 41 meters/second to the velocity.

ugordan
2009-Aug-06, 06:52 PM
[I]Playing with this delta-v calculator (http://www.strout.net/info/science/delta-v/intro.html), if the loaded mass is 25,000 KG and the Isp is 320 seconds (about right for a hypergolic SM), then it takes 3000 KG of propellant to add 41 meters/second to the velocity.

That calculator is clearly wrong, the value doesn't even pass a sanity check. I plugged the figures into the rocket equation directly and using your loaded mass and Isp I need 400 kg of propellant for 50 m/s delta-V. Much smaller than your value, but still not exactly something to sneeze at.

For the Ares I overweight upper stage this could actually be a performance gain, even though lower Isp is involved, but for a Centaur-like stage my guess is you'd get more delta-v from simply having 400 kg more of LH2/LOX loaded.

Antice
2009-Aug-06, 07:19 PM
the Orion SM is projected to carry 7924kg/17433LBS of propellant when configured for a lunar mission.... 400kg while not insignificant is not a major Delta-v factor. most of it is budgeted for the return journey.

link to Orion reference sheet @NASA (http://www.nasa.gov/pdf/306407main_orion_crew%20_expl_vehicle.pdf)

added to avoid a double post:
I am always astonished at just how large a fraction of the orion is dedicated to fuel on lunar missions. there are really a lot of manoeuvring that has to be done by the CEV during a lunar mission.
The block I version for ISS use is loads lighter on fuel use despite having more payload/crew.

ugordan
2009-Aug-06, 07:39 PM
the Orion SM is projected to carry 7924kg/17433LBS of propellant when configured for a lunar mission.... 400kg while not insignificant is not a major Delta-v factor. most of it is budgeted for the return journey.

link to Orion reference sheet @NASA (http://www.nasa.gov/pdf/306407main_orion_crew%20_expl_vehicle.pdf)

Even better, Orion at 21.7 tons total in orbit for lunar missions, that would likely allow an Atlas V HLV direct injection of the entire stack to orbit and by blowdown of the rest of Centaur propellant (from those extra few payload tons of unused flight performance reserve) the latter could be deorbited safely. That's actually standard procedure for Centaur-payload collision avoidance maneuvers.

Why waste those 5% of Orion propellant if it's not really necessary? ISS Orion doesn't need to do TEI burns or potential direct aborts so it doesn't need to carry as much fuel. LEO Apollos didn't either, especially those launched on Saturn Ib.

This isn't really pushing for Atlas V HLV as much as a demonstration of capability the U.S. already effectively has, but that (same or slightly lower) capability is being redeveloped at NASA at *vastly* higher cost.

Antice
2009-Aug-06, 07:49 PM
Someone some place at NASA made a decision a long time ago that manned launchers should release their second stage before reaching orbit. this is the way the shuttle has been doing it for years and the same profile is wanted for orion.
one of the advantages of this is that if the orion SM were to fail the orion would re-enter balistically no matter what. call it a last second passive abort mode if you want but it makes it possible for an abort even after stage 2 sep at the apex of the launch trajectory.

RGClark
2009-Aug-06, 08:48 PM
EDIT: In fact, I've just found the data in the Atlas V Mission Planner's Guide the LEO performance of an Atlas V HLV with a dual-engine Centaur and to an 28.5 degree inclination, 185 km circular orbit is 29.4 tons. Beat that, Ares I!

Do you have a reference for that? I was going by the article referenced by Larry that the Atlas V 401 would only be able to lift 20,100 lb, about 10 mT, to orbit.


Bob Clark

Larry Jacks
2009-Aug-06, 09:01 PM
Do you have a reference for that? I was going by the article referenced by Larry that the Atlas V 401 would only be able to lift 20,100 lb, about 10 mT, to orbit.

You're comparing the Atlas V 401 to the Atlas V Heavy. Those are very different rockets. From Astronautix.com (http://www.astronautix.com/lvs/atlasv.htm), the Atlas V 401 can put 12,500 KG into a 28 degree inclination LEO orbit. The Atlas V 501 can put up 20,050 KG into the same orbit. According to this source (http://en.wikipedia.org/wiki/Atlas_V), the Atlas V Heavy (5H2) can put 25,000 KG into LEO.

GeorgeLeRoyTirebiter
2009-Aug-06, 09:01 PM
Do you have a reference for that? I was going by the article referenced by Larry that the Atlas V 401 would only be able to lift 20,100 lb, about 10 mT, to orbit.

Um...


EDIT: In fact, I've just found the data in the Atlas V Mission Planner's Guide the LEO performance of an Atlas V HLV with a dual-engine Centaur and to an 28.5 degree inclination, 185 km circular orbit is 29.4 tons. Beat that, Ares I!

http://www.ulalaunch.com/docs/product_sheet/Atlas_Mission_Planner_14161.pdf

See the performance chart on page 2-31.

RGClark
2009-Aug-06, 09:02 PM
That calculator is clearly wrong, the value doesn't even pass a sanity check. I plugged the figures into the rocket equation directly and using your loaded mass and Isp I need 400 kg of propellant for 50 m/s delta-V. Much smaller than your value, but still not exactly something to sneeze at.

For the Ares I overweight upper stage this could actually be a performance gain, even though lower Isp is involved, but for a Centaur-like stage my guess is you'd get more delta-v from simply having 400 kg more of LH2/LOX loaded.

Yeah, that calculator seems to give the right answer when you input the exhaust velocity, Vex, in the third entry box, but the wrong answer when you use the specific impulse option in that box.


Bob Clark

RGClark
2009-Aug-06, 10:00 PM
Um...



http://www.ulalaunch.com/docs/product_sheet/Atlas_Mission_Planner_14161.pdf

See the performance chart on page 2-31.

Thanks for that. That's a pretty large file, 32 Mbyes, and 401 pages.
The Atlas V HLV is proposed to use 3 RD-180 engines. This will give the first stage a thrust close to 3,000,000 lb so comparable to the Ares I solids, but at a much less dry weight, so should be able to exceed the Ares I payload to orbit.

So there are several options if the Ares I solids are to be replaced with liquid fueled engines for manned missions. All of these could surpass the Ares I in payload to orbit:

1.)Replace the solids with a single RD-171. This engine has been used many times, but is a Russian engine. It would be cheaper. But I consider it unlikely that the U.S. would want to be dependent on a Russian engine for all manned flights for a long period.

2.)Replace the solids with two RD-180's and keep the J-2X engine now proposed for the Ares I upper stage. The RD-180 has been contracted at least to be made by an American manufacturer, Pratt & Whitney, but I'm informed none have actually been made in the U.S.
This would be more palatable to be used for all near term manned missions if the ones used are made in the U.S. The fact there are two needed would increase the cost as well as the fact they would be made by an American company.

3.)Use the Atlas V HLV with 3 RD-180's for the lower stage, with the RL-10A, perhaps two of them, for the upper stage. Using 3 RD-180's would be more expensive but you might save on the cheaper RL-10A's for the upper stage compared to the J-2X.

4.)Restart development of the RS-84. Two of these would give comparable performance to using 2 RD-180's with a J-2X powered upper stage. This would be reusable so it gives you some more options for saving money if a flyback booster capability is developed. Main disadvantage is that it's still not completed. You would then have to figure also development costs.

Cheapest option is undoubtedly #1. But I consider it politically impossible.
My personal preferred option is #4 because it would be an American engine and also because it would be reusable, though very likely more expensive than the others.


Bob Clark

RGClark
2009-Aug-09, 07:14 AM
So there are several options if the Ares I solids are to be replaced with liquid fueled engines for manned missions. All of these could surpass the Ares I in payload to orbit:
1.)Replace the solids with a single RD-171. This engine has been used many times, but is a Russian engine. It would be cheaper. But I consider it unlikely that the U.S. would want to be dependent on a Russian engine for all manned flights for a long period.
2.)Replace the solids with two RD-180's and keep the J-2X engine now proposed for the Ares I upper stage. The RD-180 has been contracted at least to be made by an American manufacturer, Pratt & Whitney, but I'm informed none have actually been made in the U.S.
This would be more palatable to be used for all near term manned missions if the ones used are made in the U.S. The fact there are two needed would increase the cost as well as the fact they would be made by an American company.
3.)Use the Atlas V HLV with 3 RD-180's for the lower stage, with the RL-10A, perhaps two of them, for the upper stage. Using 3 RD-180's would be more expensive but you might save on the cheaper RL-10A's for the upper stage compared to the J-2X.
4.)Restart development of the RS-84. Two of these would give comparable performance to using 2 RD-180's with a J-2X powered upper stage. This would be reusable so it gives you some more options for saving money if a flyback booster capability is developed. Main disadvantage is that it's still not completed. You would then have to figure also development costs.
Cheapest option is undoubtedly #1. But I consider it politically impossible.
My personal preferred option is #4 because it would be an American engine and also because it would be reusable, though very likely more expensive than the others.


5.)Use a variant of the Delta IV Heavy. This was discussed in the thread on this forum: Aviation Week article: "NASA Study Finds Human-rated Delta IV Cheaper". The Delta IV Heavy is an already existing launcher that can lift the 25,000 kg payload of Ares I to orbit:

Delta IV
http://www.astronautix.com/lvs/deltaiv.htm

The report by the Aerospace Corp. discussed in that Aviation Week article argued it would be cheaper to man-rate this launcher than to proceed with the Ares I. However, even this report notes it would take 5-1/2 to 7 years to make the modifications to man-rate the Delta IV Heavy.
This was viewed as adding an additional two year gap for manned missions after the end of shuttle flights. But that was assuming Ares I could make the 2015 schedule for start of its flights. It's becoming increasingly likely that Ares I also won't be able to fly until 2017 or later.
Given the up to 7 year delay in man-rating the Delta IV Heavy perhaps once again a cancelled reusable engine should have its development re-started. This is the RS-83. Like the RS-68 used on the Delta IV Heavy, this is a liquid hydrogen/LOX engine. It was intended as a reusable upgrade to the RS-68. Since the RS-83 was already intended to be used also on manned flights the man rating process should be simpler.
The question is how much would it cost to complete the development and could it be ready to match the likely 2017 start date for Ares I?


Bob Clark

ugordan
2009-Aug-09, 11:31 AM
Given the up to 7 year delay in man-rating the Delta IV Heavy perhaps once again a cancelled reusable engine should have its development re-started.
What would you do with that engine?

RGClark
2009-Aug-09, 03:16 PM
What would you do with that engine?

The RS-83 would have about the same thrust as the RS-68 currently used on the Delta-IV Heavy but is lighter. The most important difference is that it is reusable.
The RS-83 and the kerosene fueled RS-84 were intended to cut costs by being reusable to be used on a flyback booster for example.
The Air Force began development of such flyback boosters in 2005, with an intended first flight by 2010, oddly enough also referred to as ARES:

Ares FBB.
"Winged orbital launch vehicle. Family: Winged. Country: USA. Status: Development.
The ARES ((Affordable REsponsive Spacelift) concept was of a reusable fly-back booster with expendable upper stages. The US Air Force began development of a demonstrator in May 2005, with a first flight date of 2010. It was felt that derivatives of the concept could support all space lift requirements of the USAF."
http://www.astronautix.com/lvs/aresfbb.htm

Obviously the 2010 first flight date won't be met. But the Air Force is funding development of flyback first stage boosters with its proposed "Reusable Booster System", as I discussed in this earlier post:

http://www.bautforum.com/space-exploration/86728-passenger-market-suborbital-hypersonic-transports-6.html#post1500696

The key reason why I favor the RS-83 or RS-84 engines, or both, is because they could be used for such reusable first stage flyback boosters. The Air Force studies estimate using such reusable boosters for the first stage while keeping expendable upper stages could cut launch costs by 50%. They would also be much cheaper to develop since you don't have the problem of reentry at orbital velocity, Mach 25 or so. Some versions only have to go to Mach 3.5, a comparable reentry problem as to the low cost SpaceShipOne.
These programs seem to have separate funding from the Air Force than NASA manned flight programs. Then the costs to NASA could be cut, if the Ares I solids were to be replaced, by sharing the costs with the Air Force of the RS-83/84 development.

Edit: a nice side benefit of this is that you could also save on acronyms. ;-)

Bob Clark

samkent
2009-Aug-09, 07:19 PM
The key reason why I favor the RS-83 or RS-84 engines, or both, is because they could be used for such reusable first stage flyback boosters.

You mean like Ares reusable boosters?

ugordan
2009-Aug-09, 07:39 PM
The RS-83 would have about the same thrust as the RS-68 currently used on the Delta-IV Heavy but is lighter. The most important difference is that it is reusable.

It would also be more expensive than RS-68. RS-68 was designed with primarily cost and low complexity in mind. It's a booster engine, not another attempt at a SSME performance and reusability, quite the opposite.

And there is already an upgrade in the works for the RS-68, the RS-68A which will increase Delta IV performance by at least 10%.

There is no benefit to a reusable engine on a Delta IV as it's an expendable vehicle. What's the point of spending hundreds of millions of $ developing that engine if the CBCs will end up in the drink downrange anyway? It's certainly not going to make the manned flight gap any shorter nor an alternative cheaper. Not to mention the hassle, cost and performance hit of making Delta IV CBCs flyback boosters.

If the U.S. really chooses (for one reason or another) to develop a new engine, it should be a high thrust kerolox engine. If this situation has shown anything it's that U.S. sorely lacks powerful liquid booster engines and boosters are where RP-1 excels, not hydrogen - compare Atlas V to Delta IV booster stages in both cost, tankage size and flight rates.
This obsession with hydrogen as first stage is frankly puzzling to me - U.S. already has RS-68(A) and SSME. The latter could be made expendable, lowering its cost and making it "just" 2x as expensive as a RS-68, but with significantly greater performance (and lower thrust). There is no need for Yet Another Hydrogen Booster Engine.

RGClark
2009-Aug-10, 04:47 AM
It would also be more expensive than RS-68. RS-68 was designed with primarily cost and low complexity in mind. It's a booster engine, not another attempt at a SSME performance and reusability, quite the opposite.
And there is already an upgrade in the works for the RS-68, the RS-68A which will increase Delta IV performance by at least 10%.
There is no benefit to a reusable engine on a Delta IV as it's an expendable vehicle. What's the point of spending hundreds of millions of $ developing that engine if the CBCs will end up in the drink downrange anyway? It's certainly not going to make the manned flight gap any shorter nor an alternative cheaper. Not to mention the hassle, cost and performance hit of making Delta IV CBCs flyback boosters.
If the U.S. really chooses (for one reason or another) to develop a new engine, it should be a high thrust kerolox engine. If this situation has shown anything it's that U.S. sorely lacks powerful liquid booster engines and boosters are where RP-1 excels, not hydrogen - compare Atlas V to Delta IV booster stages in both cost, tankage size and flight rates.
This obsession with hydrogen as first stage is frankly puzzling to me - U.S. already has RS-68(A) and SSME. The latter could be made expendable, lowering its cost and making it "just" 2x as expensive as a RS-68, but with significantly greater performance (and lower thrust). There is no need for Yet Another Hydrogen Booster Engine.

CBC stands for "common booster core". This is a lower stage engine. With the Air Force's "Reusable Booster System", the lower stage would be reusable. This would be a completely different system than the Delta IV.
The RS-84, also proposed as a high thrust reusable engine, is kerosene fueled. It was further along in development before cancellation than the RS-83, which is hydrogen fueled. The Air Force also prefers kerosene-fueled engines for its flyback boosters. Then the RS-84 may be the quickest and cost effective way for NASA to get a liquid fueled replacement for the Ares I solids.


Bob Clark

ugordan
2009-Aug-10, 08:43 AM
CBC stands for "common booster core". This is a lower stage engine. With the Air Force's "Reusable Booster System", the lower stage would be reusable. This would be a completely different system than the Delta IV.
The RS-84, also proposed as a high thrust reusable engine, is kerosene fueled. It was further along in development before cancellation than the RS-83, which is hydrogen fueled. The Air Force also prefers kerosene-fueled engines for its flyback boosters. Then the RS-84 may be the quickest and cost effective way for NASA to get a liquid fueled replacement for the Ares I solids.

I'm aware of all this, but I guess I just don't follow your line of thinking. You started off with "So there are several options if the Ares I solids are to be replaced with liquid fueled engines for manned missions. All of these could surpass the Ares I in payload to orbit" and you then propose these new developments that would possibly take much longer to field than even Ares I would take.

I guess I don't see the benefit of ditching Ares I in favor of new engines and boosters in the short term. You'd be back to square one. ULA is talking about 2030 timeframe for fielding RBS, that's not something in the near future. In the long term, if you're planning on dumping the SRB first stage, you can drop Ares I completely because switching 1st stage boosters will impact the upper stage size if you really want optimized performance to LEO and not yet another kludge rocket.

GeorgeLeRoyTirebiter
2009-Aug-10, 10:24 PM
Sorry to tell you this, Bob, but Congress killed the Air Force's reusable booster program back in 2006. It was being developed under a very nebulous goal (Operationally Responsive Space), and since the AF had been unable to define exactly what ORS was, Congress did it for them. The result, instead of a reusable booster, is the TacSat (http://www.astronautix.com/craft/tacsat2.htm) program: small, rapidly-deployable military satellites to be launched on Falcon I or Minotaur LVs.

RGClark
2009-Aug-13, 07:05 PM
Sorry to tell you this, Bob, but Congress killed the Air Force's reusable booster program back in 2006. It was being developed under a very nebulous goal (Operationally Responsive Space), and since the AF had been unable to define exactly what ORS was, Congress did it for them. The result, instead of a reusable booster, is the TacSat (http://www.astronautix.com/craft/tacsat2.htm) program: small, rapidly-deployable military satellites to be launched on Falcon I or Minotaur LVs.

Though the Air Force's ARES FBB booster program was cancelled, it is essentially resurrected with their "Reusable Booster System" program.

An odd phrase in the Air Force request for proposals on their flyback boosters program:

USAF Seeks Reusable Booster Ideas.
May 14, 2009
By Graham Warwick
"AFRL's reference concept includes an integral all-composite airframe and tank structure that carries both internal pressure and external flight loads. The concept vehicle is powered by pump-fed liquid-oxygen/hydrocarbon rocket engines.
"While other vehicle concepts can be proposed in response to the RFI, the solicitation says 'it is preferred for the flight demonstrator to use a previously developed main engine ... [with a] configuration similar to the expected operational system.'"
http://www.aviationweek.com/aw/generic/story_channel.jsp?channel=space&id=news/Reuse051409.xml

What already developed reusable, LOX/hydrocarbon rocket engines are there?
Of the reusable rocket engines currently operational the only ones I know of are the LOX/LH engines of the space shuttle and the liquid/solid hybrid engines of SpaceShipOne. Neither use LOX/hydrocarbon.
Earlier reusable ones were those of the X-15, which used LOX/ammonia and of the NF-104 which used H2O2/kerosene. Neither quite LOX/hydrocarbon.
I suppose you could make them LOX/hydrocarbon if you changed either the oxidizer or fuel for either.
Is the Air Force proposing to use 50-year-old-designed engines for their new flyback boosters?
It seems to me a more reasonable proposal would be to restart development of engines such as the RS-84 meant to be used on flyback first stage boosters, and for which costs could then be shared by the Air Force and NASA.


Bob Clark

GeorgeLeRoyTirebiter
2009-Aug-13, 09:44 PM
There's nothing odd about that recommendation at all. It only applies to the possible subscale flight demonstrator. X-planes are usually built using as many "off the shelf" components as possible to keep costs down.

Also, it's not a Request for Proposals, it's a Request for Information (basically, "help us come up with ideas"). The respondents won't be awarded contracts. Any possible RFPs for the subscale demonstrator will come later.

So the AFRL is looking for suggestions on a development program for a technology demonstrator that might then lead to development of an operational vehicle. Aries I will live or die long before the descendants of this program put even a single gram of payload into orbit.

RGClark
2009-Aug-16, 04:05 PM
Though the Air Force's ARES FBB booster program was cancelled, it is essentially resurrected with their "Reusable Booster System" program.

An odd phrase in the Air Force request for proposals on their flyback boosters program:

USAF Seeks Reusable Booster Ideas.
May 14, 2009
By Graham Warwick
"AFRL's reference concept includes an integral all-composite airframe and tank structure that carries both internal pressure and external flight loads. The concept vehicle is powered by pump-fed liquid-oxygen/hydrocarbon rocket engines.
"While other vehicle concepts can be proposed in response to the RFI, the solicitation says 'it is preferred for the flight demonstrator to use a previously developed main engine ... [with a] configuration similar to the expected operational system.'"
http://www.aviationweek.com/aw/generic/story_channel.jsp?channel=space&id=news/Reuse051409.xml

What already developed reusable, LOX/hydrocarbon rocket engines are there?
Of the reusable rocket engines currently operational the only ones I know of are the LOX/LH engines of the space shuttle and the liquid/solid hybrid engines of SpaceShipOne. Neither use LOX/hydrocarbon.
Earlier reusable ones were those of the X-15, which used LOX/ammonia and of the NF-104 which used H2O2/kerosene. Neither quite LOX/hydrocarbon.
I suppose you could make them LOX/hydrocarbon if you changed either the oxidizer or fuel for either.
Is the Air Force proposing to use 50-year-old-designed engines for their new flyback boosters?
It seems to me a more reasonable proposal would be to restart development of engines such as the RS-84 meant to be used on flyback first stage boosters, and for which costs could then be shared by the Air Force and NASA.




Glad to see the Augustine commision is at least considering the development of a new heavy thrust kerosene engine:

Loss of Ares I work wouldn't end world.
Sunday, August 16, 2009 By Shelby G. SpiresTimes Aerospace Writer
"For example, the commission reviewed proposals that would ask contractors to build an engine that would use liquid oxygen and kerosene, also known as rocket fuel RP-1, to power a "rocket that might not look like the Saturn V, but would be similar," said Ed Crawley, a panel member.
"This is the same type of engine as the F-1 engine that was used on the first-stage booster of the Saturn V and got the rocket 38 miles high in the Earth's atmosphere on its trip to the moon. Flying at more than 17,000 miles per hour, the space shuttle rockets can only take humans and cargo into low Earth orbit, but a Saturn V-type rocket can zoom to more than 22,000 miles per hour - fast enough to escape the tug of Earth's gravity - and put astronauts on a course to the moon."
...
"Panel members pointed out that developing an F-1 type engine would move American rocket companies away from relying on Russian technology, which creates complex legal and trade issues because Russia does business with Iran and North Korea.
"There are some negatives to developing a new engine like the F-1, Augustine panel members said, because America has not developed this type of engine for almost 50 years.
"Dennis Wingo, a Hunts-ville space entrepreneur who has worked for NASA and the University of Alabama in Huntsville, said starting a new engine design could become another half-finished program, just like the Ares I might become.
"Developing an F-1 class engine would be a marvelous idea as the (commercial rocket) program needs it. However, for a heavy lifter for the exploration program, it has the same problem that all the other heavy lift ideas have - lack of money,' Wingo said last week."
http://www.al.com/news/huntsvilletimes/local.ssf?/base/news/125041416099560.xml&coll=1&thispage=2

The development costs wouldn't need to be exorbitant however, if the construction was of engines that already had significant development work already done. I mentioned the Boeing/RocketDyne RS-84 that conceivably could have a prototype model by 2012 if restarted this year.
Another was the Northrup Grumman TR107:

TR107 Engine Component Technologies.
http://www.nasa.gov/centers/marshall/pdf/172380main_tr107.pdf

This article from 2002 stated the development costs for two heavy thrust liquid fueled prototyoes would cost $1.3 billion:

TICKET TO RIDE.
"Potential replacements for the Space Shuttle
are taking shape as NASA struggles to finalise
the requirements for a second-generation
reusable launch vehicle."
GRAHAM WARWICK / WASHINGTON DC
8-14 OCTOBER 2002 FLIGHT INTERNATIONAL
"Engine development"
"The success of our architecture depends
on the success of NASA's engine development
programme," says Young. The space
agency is funding work on four main
engine candidates, two hydrogen fuelled
and two kerosene-fuelled. Pratt &
Whitney and Aerojet are developing
the Cobra, a 600,0001b-thrust (2,670kN)
hydrogen-fuelled, staged-combustion, firstand
second-stage engine, while Boeing's
Rocketdyne division is working on the
650,0001b thrust-class RS-83. Rocketdyne
is also pursuing the RS-84, a kerosene fuelled,
staged-combustion, first-stage
engine generating 1,100,0001b thrust,
while TRW is developing the 1,000,0001b
thrust-class TR107.
The plan is to test two prototype
engines at a cost of $1.3 billion. "NASA will
go for prototype engines that bracket the
requirements of the three contractors,"
says Ford. He suggests the emphasis has
shifted towards the kerosene-fuelled
engines. "NASA wants to address kerosene
first to reduce risk," he says. The USA has
little experience with kerosene-burning
rocket motors, having focused for decades
on cryogenic engines."
http://www.flightglobal.com/pdfarchive/view/2002/2002%20-%202996.html

Note that the original development cost for the Ares I lower stage was slated as $1.8 billion, though the development fixes likely have increased that value.
SpaceShipOne showed that a flyback booster could be developed at low cost as long as the velocity could be kept in the Mach 3-4 range so that the reentry heating is much less.
This speed range is one of the possibilities the Air Force is considering for their flyback booster program. Then the development costs of the engine as well as the flyback airframe could be shared by NASA and the Air Force.
Actually considering how Scaled Composites was able to get SpaceShipOne done at such low cost it might be better to let them handle the design of the airframe rather than assigning it to the usual big aerospace companies with their usual accompanying, ballooning cost overruns.


Bob Clark

RGClark
2009-Aug-18, 08:48 PM
Just saw this article that says Ares I is all but certain to get cancelled:

John Kelly: Is Ares I work all for nothing?
As milestone passes, billions wasted if rocket is canceled.
BY JOHN KELLY • FLORIDA TODAY • August 17, 2009
"...The evening before KSC workers finished putting the first Ares I together, a panel of President Barack Obama's space advisers all but canceled Ares I and maybe even scuttled the whole moon-Mars program.
"NASA nevertheless is under orders to press ahead with Ares until the president makes a decision. That work is costing you about $300 million a month."
...
"Whatever the future holds for NASA, folks in Washington are near a consensus that the Ares I rocket has no place in it. That shiny new test model stacked and almost ready to fly at KSC might never roll to the pad. NASA and the taxpayers will again see a multibillion-dollar bid to replace the shuttles felled by the budget ax."
http://www.floridatoday.com/article/20090817/NEWS02/908170312/1006/NEWS01/John+Kelly++Is+Ares+I+work+all+for+nothing

The problems with Ares I stem largely from the solid rocket first stage. The money spent on the upper stage including the crew vehicle would not need to have been wasted if it is retained while replacing the first stage solids with reusable liquid-fueled engines.
Even the money already spent on the solids need not have been wasted if the decision is made to still use solid rocket boosters on Ares V.
I don't rule this out, but my view is that we need to move forward to having reusable flyback boosters, certainly at least for the Ares I replacement.


Bob Clark

Antice
2009-Aug-18, 08:59 PM
I stil havent seen anything that can be finished sooner and cheaper. not the lunar variant at least. SpaceX can have something up 2,5 years after getting the go ahead. but that would take government funding for the LES needed for the dragon. but the dragon isnt being designed for lunar operations.
I get the impression that the entire VSE is being scrapped. And Ares is being scrapped as a consequence of that. not the other way around.

RGClark
2009-Aug-19, 03:36 PM
My opinion, NASA was not being foresightful when it cancelled some programs that could have prevented the Ares I mess:

NASA cancels technology development programs.
Posted: Fri, Mar 19, 2004, 7:42 AM ET (1242 GMT)
"NASA has started canceling technology development programs that don't fit the needs of the new space initiative, including a hypersonic flight program and a new reusable engine, a top NASA official said Thursday. Craig Steidle, the associate administrator for NASA's new Office of Exploration Systems, told members of the space subcommittee of the House Science Committee on Thursday that the agency has completed a review of all 140 technology development programs run by the agency. Under questioning by Rep. Nick Lampson (D-TX), Steidle said that the agency had cancelled both the X-43C and the RS-84 programs. The X-43C, a joint project with the Air Force Research Laboratory, was a hypersonic flight test program that was designed to follow on from the X-43A program currently in progress, while the RS-84 was a large reusable rocket engine being developed by Rocketdyne under a project that dated back to the Space Launch Initiative. Steidle said that neither program met the needs of the exploration program at this time. He did not specify when those programs were cancelled, but earlier in the week officials with the exploration office said that they had completed the review of all their technology programs at the end of last week. Steidle had previously stated that the agency planned to drop those technology programs that did not meet the agency's exploration needs, but that new programs would be started to fill in the gaps identified in the review."
http://www.spacetoday.net/Summary/2263

The Air Force is moving ahead with its hypersonic research with flight tests coming up in October. Successful ground tests give confidence in the success of the flight tests.
The Air Force is also recommending implementation of flyback boosters for its future launchers. For the heavy lift missions this will require heavy thrust, reusable engines. The RS-84 heavy thrust engine would have had protoypes available by 2007 if development had not been cancelled. And its active service could have commenced well before the 2015 proposed start date of Ares I, perhaps even before the 2010 planned ending of shuttle flights.
These systems are forward looking and certainly within the range of current technical understanding. Plus, they would have allowed the developmental costs to be shared by the Air Force. Yet the decision was made to go backwards and use solid rocket engines.
I believe this decision was largely due to this architecture being proposed by former administrator Mike Griffin. And with Griffin as the administrator this decision was perpetuated despite its numerous shortcomings. Moreover, this fact discouraged dissent because it was the understanding it was the agency's head boss's baby.

Bob Clark

samkent
2009-Aug-19, 04:46 PM
Hypersonic flight?
Re useable engine?

After the Augustine commissions report it doesn’t sound like we need either. So in my eyes they did the right thing back in ‘04’.

And for the flyback booster, they are seeking ‘ideas’. That’s a long way from designing and even farther from building. With today’s budget, I doubt it will get any farther than ideas stored in a folder, in the back of a filing cabinet.

RGClark
2009-Aug-19, 05:48 PM
Hypersonic flight?
Re useable engine?

After the Augustine commissions report it doesn’t sound like we need either. So in my eyes they did the right thing back in ‘04’.

And for the flyback booster, they are seeking ‘ideas’. That’s a long way from designing and even farther from building. With today’s budget, I doubt it will get any farther than ideas stored in a folder, in the back of a filing cabinet.


You assuming none have been designed or built. Several have been designed both in this country and in Russia. And at least one in this country is undergoing scale flight tests.


Bob Clark

RGClark
2009-Aug-19, 06:00 PM
You assuming none have been designed or built. Several have been designed both in this country and in Russia. And at least one in this country is undergoing scale flight tests.

And of course aside from these SpaceShipOne proved reusable flyback boosters work.

Bob Clark

ugordan
2009-Aug-19, 06:10 PM
And of course aside from these SpaceShipOne proved reusable flyback boosters work.

How so? Neglecting the fact that true booster stages also propel an upper stage and payload (which have considerable mass), not only themselves, to high speed, flying at Mach 3 is a very different story than Mach 8 typically achieved by rocket 1st stages. EELV booster stages most likely go even faster at burnout.

Mach 8 is over 7 times the energy the thermal protection system has to endure over Mach 3 on reentry. That scales up mass and imposes significant hits on 1st stage weights and ultimately the payload.

I'm not saying flyback boosters are impossible by a long shot, but calling SS1 proof of the concept is IMHO stretching it a bit.

samkent
2009-Aug-19, 06:31 PM
And of course aside from these SpaceShipOne proved reusable flyback boosters work.

If you are talking about the White Knight, it's hardly apples to apples.

Nicolas
2009-Aug-20, 07:30 AM
A single SRB first stage Ares IX will be tested soon. So will the 5 segment SRB (ground test).

It may be wise to wait until after these test before shouting how this SRB is a problem for Ares I.

cjl
2009-Aug-20, 08:11 AM
They've already tested a 5 segment on the ground, though I'm pretty sure it's a different propellant geometry and nozzle:

http://www.youtube.com/watch?v=BSPXSjQ5b-U

Nicolas
2009-Aug-20, 08:36 AM
In october they'll test the final design 5 segment SRB on the ground, as far as I understood.

I can't watch youtube from here, so I don't know which test is shown there.

RGClark
2009-Aug-21, 02:45 PM
Augustine Panel takes final options to White House staff
posted by Robert Block on Aug 14, 2009 11:44:48 AM
"The Constellation program in all of its guises is presumed to have scored very low, a sign that NASA’s work for the last four years on the Ares I and Ares V rockets and the Orion crew capsule may be stillborn.
"According to panel insiders, until yesterday committee members were working hard to make option 5b -- the flexible deep space option to explore the solar system using an EELV -- fit more closely to the budget. This option would likely relay on a rocket with a liquid oxygen and kerosene engine that would be designed and operated by a commercial company and bought by NASA."
http://blogs.orlandosentinel.com/news_space_thewritestuff/2009/08/augustine-panel-takes-final-options-to-white-house-staff.html

In the now closed thread "Should we consider Ares I out of the game?" I raised the possibility that the "designed and operated by a commercial company" LOX/kero rocket mentioned could be the Falcon 9.
However, I just looked up some info on the Falcon 9:

Falcon 9.
http://en.wikipedia.org/wiki/Falcon_9

It uses 9 Merlin engines of only 125,000 sea level thrust. I find it unlikely that NASA would want to use a cluster of 9 engines for its manned launches. Creating a version of nearly 10 times greater thrust is also not merely a matter of scaling. It nearly requires an entire new design. That would be quite expensive and time consuming. I find it unlikely NASA would assign that gargantuan task to SpaceX.
SpaceX also intends to makes these engines be reusable by sea recovery. I found it even more unlikely NASA would trust delicately balanced, high thrust engines used on manned launches to undergo sea recovery. High pressure turbopumps with their quite exacting tolerances used on such engines are something very different that just solid rocket motor casings.
That leaves us again with the RS-84 or the TR107 engines that have already udergone partial development. And again if these reusable engines are used it would be extremely wasteful not to use flyback boosters to reuse them.


Bob Clark

Antice
2009-Aug-21, 03:41 PM
SpaceX had to salt water certify their engines in order to use the Kwajalein launch site.
that island is nothing more than a pile of sand far out on the ocean after all.
They should not degrade noticeably by being immersed in salt water during recovery.
to be fair. they paid a lot to learn that they needed to proof their rocket against salt corrosion by having their first launch fail like that.
Even when not reused the Falcon engine seems to be performing cheaply enough to allow cheaper launches compared to some of the oldspace stuff out there.
Oh btw. one do not need anything bigger than dragon if one is to use EOR on the return trip. altho there is a fuel penalty there. the fuel penalty may be offset somewhat by having a reusable EDS/Moon shuttle

ugordan
2009-Aug-21, 03:58 PM
I find it unlikely that NASA would want to use a cluster of 9 engines for its manned launches.

This misconception arises often so maybe a few thoughts on the issue:

1) NASA had no problem putting the Apollo 7 crew on top of a Saturn Ib which had 8 first stage engines.

2) NASA had no problem putting crews on Saturn V which had a total of 11 engines. Only 5 of which were covered by the LES system. Then think about the Apollo 13 2nd stage center engine violent pogo and how the crew could have very well became toast because at that point the LES was long gone. Falcon 9/Dragon with a LAS would cover you for any of 9 out of 10 engine failures.

3) Falcon 9 claims to have engine out capability on first stage. Assuming non-explosive failures (and there really is no reason in recent history to assume otherwise), that would actually increase mission reliability. On an Atlas V if you lose the RD-180, it's over. Falcon 9 has higher chances of losing an engine, but that is offset by the fact a loss of one engine is not automatically a loss of mission.

There are valid concerns about the Falcon 9, the biggest of which is it's unproven (by that I mean an appreciable flight history, not one successful flight), but the number of engines on the first stage isn't one.

Now, the Falcon 9 Heavy is arguably a different story...


SpaceX also intends to makes these engines be reusable by sea recovery. I found it even more unlikely NASA would trust delicately balanced, high thrust engines used on manned launches to undergo sea recovery.
I don't think anyone's suggesting launching humans on recovered first stage boosters. Those would be flown (if recovery ever pans out) on unmanned launches which would probably be the majority anyway. Similar to reflying cargo Dragons as DragonLabs.

On a slightly related topic, a video via NSF.com of the acceptance test of a first stage engine is here (http://picasaweb.google.com/hopefig6/EngineFire#5359548478183818754). If you click the higher quality video you can actually see the engine gimbal test at ~22 seconds.

Antice
2009-Aug-21, 04:02 PM
The Heavy is unlikely to ever become what it looks like now. Elon Musk has been hinting about having a dev program on the back burner for a Big Falcon Engine to reduce the number of engines used for F9 and F9 heavy.
The F9 heavy as it is currently depicted would have triple engine out capability tho.

Larry Jacks
2009-Aug-21, 05:53 PM
The F9 heavy as it is currently depicted would have triple engine out capability tho.

I don't know if that's really an accurate assessment. It might be possible of a Falcon 9 Heavy to lose 3 engines but I suspect it depends on how the loss occurs. For example, if it lost 3 engines on one of the outboard boosters, I doubt the rocket would have sufficient steering authority to maintain control with such an asymmetric thrust load. It might survive losing 3 engines in the center booster, or one in each, or perhaps 2 on one side and one on the other. All I'm trying to say is that I doubt it could survive any possible 3 engine out situation but perhaps could survive certain engine out configurations.

ugordan
2009-Aug-21, 06:27 PM
For example, if it lost 3 engines on one of the outboard boosters, I doubt the rocket would have sufficient steering authority to maintain control with such an asymmetric thrust load.
I don't think control authority would be the biggest problem, at least long before burnout of the boosters. 24/27 engines still provide much authority, total thrust vector would need to be biased to pass through the vehicle center of gravity. In the end it would probably tilt the vehicle slightly "sideways" with respect to the velocity vector. This wouldn't be a problem higher in the atmosphere, but lower in aerodynamic loads might be problematic.

What I'm wondering is how would the differing fuel consumption rates in L and R boosters affect controllability. Lose 3 engines early enough in one booster and by the time the other one burns out you'd still have plenty of fuel mass in the first one. CG would shift considerably when approaching to strapon burnout and that would give rise to serious controllability issues... I've wondered if the most practical solution would simply be to just kill the same number of engines on the other booster as had failed in the first one and live with it.

Core booster engine failures likely wouldn't be so problematic.

Anyway, all this is probably academic because some sources are saying they'll never field the 27 engine F9H as potential customers are uneasy with that many engines. It's likely they'll develop a bigger booster engine before flying F9H. Some recent rumors said SpaceX inquired about the RS-84 but found it too expensive so they decided to build their own engine. Yet other rumors said they actually did get a licence for RS-84. I don't really know how much all that is credible. It's certainly contradictory.

Also, I don't know if they can afford a bigger kerolox engine when they've already gone public about developing a LH2 F9 upper stage at the same time. It does seem more wise to go for the LH2 upper stage first. There aren't that many payloads that require a Heavy version anyway.

Glom
2009-Aug-21, 06:37 PM
They've already tested a 5 segment on the ground, though I'm pretty sure it's a different propellant geometry and nozzle:

http://www.youtube.com/watch?v=BSPXSjQ5b-U

Sorry to derail, but there's a comment in the YouTube thread that the military was thinking of developing the Saturn V into an ICBM. Is that true? It doesn't sound remotely plausible. First, what possible use would such a large rocket be simply for the plausible of deploying nuclear weapons on Earth? Second, they said they would convert the 1st stage to solid fuel, which is hardly a small job and in fact sounds an implausible option.

NEOWatcher
2009-Aug-21, 06:54 PM
Sorry to derail, but there's a comment in the YouTube thread that the military was thinking of developing the Saturn V into an ICBM. Is that true?
I wouldn't know, but...

It doesn't sound remotely plausible.
How plausible does it have to be to think about it to see if it were plausible?

First, what possible use would such a large rocket be simply for the plausible of deploying nuclear weapons on Earth?
Multiple warheads on multiple targets on a single launch. Although, in practicality, that sounds like putting your eggs in one basket, it might have some deterrent advantage.


Second, they said they would convert the 1st stage to solid fuel, which is hardly a small job and in fact sounds an implausible option.
Convert? Maybe develop a new first stage instead. Sounds like a big job to me, but were there solid boosters at the time that might have been able to be clustered to do the job?
I also see that NOVA (http://www.astronautix.com/lvs/nova.htm) had some solid variants.

danscope
2009-Aug-21, 07:28 PM
Sorry to derail, but there's a comment in the YouTube thread that the military was thinking of developing the Saturn V into an ICBM. Is that true? It doesn't sound remotely plausible. First, what possible use would such a large rocket be simply for the plausible of deploying nuclear weapons on Earth? Second, they said they would convert the 1st stage to solid fuel, which is hardly a small job and in fact sounds an implausible option.

**********
Sir: The military already had much better, more accurate and cheaper delivery vehicles with instantaneous response ..save spining up the gyros as opposed to Saturn V , which is extravagantly expensive..yea exhorbitant, and requires a great deal of time and attention etc etc etc. It's like using a bulldozer to deliver an ice cube.
Shirley you can't be serious.
Dan

RGClark
2009-Aug-21, 08:23 PM
...
Anyway, all this is probably academic because some sources are saying they'll never field the 27 engine F9H as potential customers are uneasy with that many engines. It's likely they'll develop a bigger booster engine before flying F9H. Some recent rumors said SpaceX inquired about the RS-84 but found it too expensive so they decided to build their own engine. Yet other rumors said they actually did get a licence for RS-84. I don't really know how much all that is credible. It's certainly contradictory.
...

So if the satellite customers don't want it, it is a virtual certainty NASA wouldn't want it for its manned missions. So we're back to a heavy thrust LOX/kero engine. It is very unlikely NASA would assign the development of such a large and expensive heavy thrust engine to a small company like SpaceX.
Then we're back again to the RS-84 or TR107.


Bob Clark

ugordan
2009-Aug-21, 08:37 PM
So if the satellite customers don't want it, it is a virtual certainty NASA wouldn't want it for its manned missions.

Where did this idea of putting humans on top of a Falcon 9 Heavy come in the first place? Who's proposing F9H for manned missions?

Dragon was always meant to ride the regular Falcon 9. I already pointed out there's nothing extraordinary about nine engines on Falcon 9.


It is very unlikely NASA would assign the development of such a large and expensive heavy thrust engine to a small company like SpaceX.

If SpaceX ever develop a high thrust booster engine, it will not be because NASA told them to build one for them, but because SpaceX plan on using it on their own booster. Besides, they wouldn't want to develop a large and expensive engine anyway, they'd want a large and inexpensive engine, possibly a kerosene version of this baby (http://sscfreedom.ssc.nasa.gov/etd/ETDPropulsionSS_TRW650K.asp). In that regard, SpaceX couldn't care less how NASA felt about their engine development. Just as they didn't care when they designed Merlin and started work on F9 and Dragon several years ago. People were laughing at them then for building a crewed capsule with "no business case".

Who's laughing now?

Antice
2009-Aug-21, 08:46 PM
It's a matter of markets. how many non government payloads does the Delta IV heavy launch annually. The F9 is looking up to be good enough for cots. and it's payload capacity is going to go up once they get to use some of the lessons learned on the first launches to do some upgrades.
I do not think there is a business case for going head to head with the other heavies just yet.

ugordan
2009-Aug-21, 08:57 PM
It's a matter of markets. how many non government payloads does the Delta IV heavy launch annually.

Non-government? None. Ever. In fact, Delta IV Heavy only flew 3 times total since December 2004 - 1 demo flight and 2 DoD missions.



I do not think there is a business case for going head to head with the other heavies just yet.
Exactly. That's also why LockMart didn't go ahead and complete development of Atlas V HLV. A Falcon 9 Block II with a Raptor LH2 stage would provide a massive performance boost over the all-kerosene version and would be enough for most satellite needs in the near future.

If the market changes to provide business for heavier lift - say boosting propellant to a depot, then Falcon 9 Heavy might have more chance of going forward.

RGClark
2009-Aug-21, 09:30 PM
I don't rule out using solids on Ares V or equivalent. Still, I would like to find out how many LOX/kero 1,000,000 lb thrust class engines it would take to get the same payload to orbit without using the solids.
This is made more difficult since the info on the Ares V upper stage is so sketchy. Anyone know the engine and mass of the upper stage for the Ares V?


Bob Clark

RGClark
2009-Aug-21, 10:02 PM
It's a matter of markets. how many non government payloads does the Delta IV heavy launch annually. The F9 is looking up to be good enough for cots. and it's payload capacity is going to go up once they get to use some of the lessons learned on the first launches to do some upgrades.
I do not think there is a business case for going head to head with the other heavies just yet.

There is a significant market for such heavy launches judging by the number of launches on other vehicles:

Comparison of heavy lift launch systems.
http://en.wikipedia.org/wiki/Comparison_of_heavy_lift_launch_systems

The larger revenue in absolute terms would come from such launches. Whether or not that amounts to greater profit depends on how low cost they can make the development of the heavy launcher.


Bob Clark

ugordan
2009-Aug-21, 10:08 PM
There is a significant market for such heavy launches judging by the number of launches on other vehicles:

What launches on what other vehicles?

Apart from the 3 Delta IV Heavies, there's not a single vehicle capable of 10+ tons to GTO that has flown even once. Ariane 5 ECA comes close to 10 tons, except it routinely flies double payloads - like tonight's launch. A testimony of it being overpowered for current needs. There is no current market for commercial satellites in the 10+ ton range.

RGClark
2009-Aug-21, 10:20 PM
What launches on what other vehicles?

Apart from the 3 Delta IV Heavies, there's not a single vehicle capable of 10+ tons to GTO that has flown even once. Ariane 5 ECA comes close to 10 tons, except it routinely flies double payloads - like tonight's launch. A testimony of it being overpowered for current needs. There is no current market for commercial satellites in the 10+ ton range.

The Falcon 9 Heavy as planned would launch 29,000 kg to LEO. This means at least it would have the payload capacity of the Ares I. Heavy lift launches are those considered able to send +20,000 kg to LEO.
The Russian Proton has this capability and has hundreds of launches. Considering the relatively low cost of Proton launches, Falcon 9 would probably have Proton as its closest competitor.


Bob Clark

ugordan
2009-Aug-21, 10:31 PM
Heavy lift launches are those considered able to send +20,000 kg to LEO.

The commercial market revolves around GEO, not LEO and virtually all missions fly to GTO trajectories. Those few that fly LEO polar missions are less massive payloads those same vehicles can carry anyway.



The Russian Proton has this capability and has hundreds of launches.

Proton has 6.5 tons capability to GTO which is closer to what a Falcon 9 with a hydrogen upper stage would do. Coincidentally, those 6.5 tons cover pretty much all commercial mass needs - take Ariane 5 launch tonight, two satellites with a total of 7 tons. 15 tons for single payloads is overkill, there's no business case for it now. It's even overkill for dual payloads. Falcon 9 Heavy with 15 tons to GTO would have an even bigger problem with payloads than Ariane 5 and with 27 engines which customers don't really prefer.

There is just no reason to go to the Falcon 9 Heavy at this point in time unless someone placed an actual order for one, just as there isn't a need for Atlas V Heavy. SpaceX is much better off concentrating on the Raptor stage in the short term to bring Falcon 9 performance closer to Proton. SpaceX may go ahead with fielding F9H anyway, but there is no business case for it now.

GeorgeLeRoyTirebiter
2009-Aug-21, 10:50 PM
The vast majority of those hundreds of launches were non-commercial Soviet military or communications satellites. Looking at the list of commercial Proton launches, the payloads are mostly in the 2-6 tonne range, well within the capabilities of the existing Atlas V variants. Much of the delta-V capability of the Proton is used in such GTO launches to compensate for the latitude of the Proton's launch site; it's heavy-lift to a 51.6° inclination but only medium-lift to more equatorial inclinations.

Captain Mike
2009-Aug-22, 03:22 PM
Slightly off topic, but NASA's got a new solid they've been testing:

http://www.scientificblogging.com/news_articles/alice_environmentallyfriendly_rocket_propellant

My story on it's better though. Funnier, anyway.

RGClark
2009-Aug-22, 07:04 PM
This article from 2002 stated the development costs for two heavy thrust liquid fueled prototypes would cost $1.3 billion:

TICKET TO RIDE.
"Potential replacements for the Space Shuttle
are taking shape as NASA struggles to finalise
the requirements for a second-generation
reusable launch vehicle."
GRAHAM WARWICK / WASHINGTON DC
8-14 OCTOBER 2002 FLIGHT INTERNATIONAL
"Engine development"
"The success of our architecture depends
on the success of NASA's engine development
programme," says Young. The space
agency is funding work on four main
engine candidates, two hydrogen fuelled
and two kerosene-fuelled. Pratt &
Whitney and Aerojet are developing
the Cobra, a 600,0001b-thrust (2,670kN)
hydrogen-fuelled, staged-combustion, firstand
second-stage engine, while Boeing's
Rocketdyne division is working on the
650,0001b thrust-class RS-83. Rocketdyne
is also pursuing the RS-84, a kerosene fuelled,
staged-combustion, first-stage
engine generating 1,100,0001b thrust,
while TRW is developing the 1,000,0001b
thrust-class TR107.
The plan is to test two prototype
engines at a cost of $1.3 billion. "NASA will
go for prototype engines that bracket the
requirements of the three contractors,"
says Ford. He suggests the emphasis has
shifted towards the kerosene-fuelled
engines. "NASA wants to address kerosene
first to reduce risk," he says. The USA has
little experience with kerosene-burning
rocket motors, having focused for decades
on cryogenic engines."
http://www.flightglobal.com/pdfarchive/view/2002/2002%20-%202996.html
...


Then if NASA chose to develop one of these, such as the RS-84, to save costs, it conceivably might only cost $650 million (!)
Then since the Air Force also wants a heavy thrust LOX/kero engine for its flyback booster program, the cost to NASA if the costs were shared might only be $325 million. NASA would only have to spend $108 million per year over 3 years to develop a reusable heavy thrust engine(!!)

My opinion, NASA needs to restart development of the RS-84 with all deliberate speed.


Bob Clark

Warren Platts
2009-Aug-22, 07:57 PM
Then if NASA chose to develop one of these, such as the RS-84, to save costs, it conceivable might only cost $650 million (!)
Then since the Air Force also wants a heavy thrust LOX/kero engine for its flyback booster program, the cost to NASA if the costs were shared might only be $325 million. NASA would only have to spend $108 million per year over 3 years to develop a reusable heavy thrust engine(!!)

My opinion, NASA needs to restart development of the RS-84 with all deliberate speed.


Bob ClarkYeah, but that would cause the whole shuttle infrastructure and people to become unemployed.

RGClark
2009-Aug-24, 06:02 AM
Then if NASA chose to develop one of these, such as the RS-84, to save costs, it conceivably might only cost $650 million (!)
Then since the Air Force also wants a heavy thrust LOX/kero engine for its flyback booster program, the cost to NASA if the costs were shared might only be $325 million. NASA would only have to spend $108 million per year over 3 years to develop a reusable heavy thrust engine(!!)
My opinion, NASA needs to restart development of the RS-84 with all deliberate speed.


X-43C, RS-84 Engine Among Casualties Of NASA Review.
Mar 19, 2004
By Jefferson Morris
http://www.aviationweek.com/aw/generic/story_generic.jsp?channel=aerospacedaily&id=news/eng03194.xml

When NASA cancelled the hypersonic X-43C and the reusable RS-84 meant for flyback boosters back in March, 2004 it undoubtedly seemed then these were far off technologies not in keeping with the Bush administration's request for near term Moon and Mars missions.
However, the Air Force in ground tests has recently successfully demonstrated hypersonic airbreathing propulsion. The success of these tests in hypersonic wind tunnels simulating real conditions gives confidence the flight tests later this year will also be successful.
Flyback boosters for two stage to orbit vehicles undoubtedly also seemed an expensive, complex proposition then. But Scaled Composites with SpaceShipOne proved, later that very same year, that as long as the flight speed is kept in the Mach 3 range to limit reentry heating, these can be developed quickly and cheaply.
The use of either of these would result in significant cuts to the costs to space. It now appears they would be the route to low cost and quick return to space that NASA wants in the wake of the shuttle retirement. And indeed their implementation could lead to the manned missions to the Moon that are desired within 10 years and in keeping with NASA's budget.
Since the Air Force already wants these and NASA needs them, I recommend a return to the costs-sharing plan intended for them under the Next Generation Launch Technology program.
The development costs for the RS-84 reusable engine needed for the heavy lift flyback boosters might be only ca. $100 million/yr over 3 years IF those costs were shared with the Air Force.
This report gives the Air Force space budget only as close to $12 billion in 2009:

FY 09 Air Force Space Budget: Modest Increase.
http://www.cdi.org/program/document.cfm?DocumentID=4201&StartRow=1&ListRows=10&appendURL=&Orderby=D.DateLastUpdated&ProgramID=68&from_page=index.cfm

I don't think there would be much hue and cry from Congress about a less than 1% change especially when it's known this small amount would solve the Ares I problem, which is a huge headache for NASA right now. That 1% of the Air Force's space budget wouldn't even have to come from an increase. The Air Force could shuffle some lower priority projects to a later period to cover it.
You can think of it as altruistic of one governmental agency to another in trouble. Or you can think of if it as good business men do of an investment that will pay for itself several times over in the future. The Air Force wants this heavy lift thruster, though several years down the road. By helping NASA pay for it now they are cutting the costs in half of what they would have had to pay for it all by themselves at probably an even higher total cost with inflation.
Note too this applies to the flyback airframes for NASA's new launchers, since the Air Force intends to use this method on all their future launchers. For their smaller satellite launchers, some projections put this as being operational by 2018 for the Air Force. Then by splitting the cost with NASA on the airframe development, they cut their costs in half and can get an earlier deployment date since NASA needs it as soon as possible. Altruism and your own bests interests sometimes go hand in hand.
The President if he really wanted to could force this. Sometimes leaders, like parents, have to make their charges make the right decisions even if at the time they don't have the good sense to make it themselves.


Bob Clark

samkent
2009-Aug-24, 01:07 PM
Flyback boosters for two stage to orbit vehicles undoubtedly also seemed an expensive, complex proposition then. But Scaled Composites with SpaceShipOne proved, later that very same year, that as long as the flight speed is kept in the Mach 3 range to limit reentry heating, these can be developed quickly and cheaply.


Uuuh Spaceship One went almost straight up for 60 miles, not into orbit. These’s a big difference in speed and altitude. Mach 22 vs mach 3. You would have to launch a very big reto rocket to drop the re entry speed back down to mach 3. So I wouldn’t say that Scaled Composites has made any break throughs. You likely could have used streamers and parashutes to re enter fro 60 miles straight up.

RGClark
2009-Aug-27, 05:34 PM
Then if NASA chose to develop one of these, such as the RS-84, to save costs, it conceivably might only cost $650 million (!)
Then since the Air Force also wants a heavy thrust LOX/kero engine for its flyback booster program, the cost to NASA if the costs were shared might only be $325 million. NASA would only have to spend $108 million per year over 3 years to develop a reusable heavy thrust engine(!!)

This article by Henry Spencer reminds me that the Air Force cleverly has the ability to resurrect launch programs previously cancelled by Congress, and in just a few short years after they were cancelled:

Failure to launch: abandoned NASA projects.
"National Launch System (NLS); 1989 – 1993; perhaps $300 million.
"This was a joint NASA-US Air Force project for a low-cost shuttle-derived expendable launcher to replace existing expendable rockets, such as Atlas, Delta and Titan launchers."
...
"After some fumbling, the US Air Force replaced it with the Evolved Expendable Launch Vehicle (EELV) programme that produced the Delta IV and Atlas V rockets. (The RS-68 engine that powers the Delta IV is probably derived from work on the "Space Transportation Main Engine" for the National Launch System.)"
http://www.newscientist.com/gallery/abandoned-nasa-projects/4

The RS-68 developed by Rocketdyne is a heavy thrust liquid hydrogen engine that powers the Delta IV Heavy. Its development cost only $500 million, it took only 5 years, and it had operational flights within only 1 year (!) after development concluded:

Boeing Completes Checks For Latest Delta IV Maiden Flight Date
Defense Daily, Oct 31, 2002
http://findarticles.com/p/articles/mi_6712/is_22_216/ai_n28953910/

This gives confidence that the RS-84 also by Rocketdyne could indeed be developed for $650 million, so only $325 million to NASA under cost-sharing with the Air Force, and perhaps have a full scale prototype model ready by 2012 if restarted this year.

The Air Force appears to have resurrected another cancelled program with the "Reusable Booster Program." This is essentially the same thing as its ARES (Affordable REsponsive Spacelift) system that was cancelled by Congress in 2006:

Ares FBB.
"Winged orbital launch vehicle. Family: Winged. Country: USA. Status: Development.
The ARES ((Affordable REsponsive Spacelift) concept was of a reusable fly-back booster with expendable upper stages. The US Air Force began development of a demonstrator in May 2005, with a first flight date of 2010. It was felt that derivatives of the concept could support all space lift requirements of the USAF."
http://www.astronautix.com/lvs/aresfbb.htm

So following the Air Force's lead, to restart the RS-84 and flyback boosters NASA just needs to call it under a different name than the "Next Generation Launch Technology" program originally used.



Bob Clark ;-)

ugordan
2009-Aug-27, 07:35 PM
Well, to those who say SRBs are better than liquids because they never cause a hold, the first Ares I 5-segment DM-1 static test in Utah was just scrubbed due to APU (powering the thrust vector control system) failure.

NEOWatcher
2009-Aug-27, 08:16 PM
Well, to those who say SRBs are better than liquids because they never cause a hold, the first Ares I 5-segment DM-1 static test in Utah was just scrubbed due to APU (powering the thrust vector control system) failure.
I can understand what you are trying to say, but this was not a rocket operating as a rocket. It was just a bench test.

Is the APU even part of the booster, or is it something attached to the booster and is part of the testing equipment?

I vaguely remember similar booster tests for the shuttle being delayed and/or going horribly wrong. Can someone confirm?

ugordan
2009-Aug-27, 08:35 PM
I can understand what you are trying to say, but this was not a rocket operating as a rocket. It was just a bench test.

Test running the same TVC hardware the shuttle flies.



Is the APU even part of the booster, or is it something attached to the booster and is part of the testing equipment?

It's part of the booster thrust vector control (TVC). Without it, there would be no controlling the shuttle stack.

I wouldn't have brought it up if it was just part of some test instrumentation.

Antice
2009-Aug-27, 08:59 PM
Well.. I'd expect them to use used modules for a test like this so it's probably not assembled nor tested to the usual standards meant for a launch. There are many ways to screw a test up. and the most common one is human sloppiness. Why go trough all the bother when the stack ain't going nowhere right?
Or i could be wrong in that a part that exist on both solid and liquid boosters does not really say much about the reliability of either compared to the other.

Does anyone know how often APU's fail in general?

ugordan
2009-Aug-27, 09:04 PM
Why go trough all the bother when the stack ain't going nowhere right?
Because it's an expensive test? Because you want the most representative data? Because it's packing a lot of firepower and could go really bad, not just for the booster but for the test stand as well if shoddy work is done and substandard components used?

Antice
2009-Aug-27, 09:15 PM
Fair enough. but the stack IS bolted down securely i presume... shoddy work on that part would be most unforgivable... while i haven't been building any rockets not done any tests on such. I have been involved in testing other systems. and i know from personal experience how fast people can become lax about stuff that at first glance might not appear relevant for what is being tested.
Was the TVC supposed to actively do anything during this test?
What impact if any would a malfunctioning TVC have on the test?
Would it impact security, or is it secured hard enough to prevent anything from flying loose short of a case rupture?

djellison
2009-Aug-28, 07:34 AM
so it's probably not assembled nor tested to the usual standards meant for a launch. There are many ways to screw a test up. and the most common one is human sloppiness. Why go trough all the bother when the stack ain't going nowhere right?

Err - not right. This is a test of hardware that is then going to become flight hardware. It has to be made, assembled, tested and verified EXACTLY like the real flight hardware, or the test is pointless.

NEOWatcher
2009-Aug-28, 12:08 PM
Err - not right. This is a test of hardware that is then going to become flight hardware. It has to be made, assembled, tested and verified EXACTLY like the real flight hardware, or the test is pointless.
How about a link to some article with details? We can be here all day long guessing what it is they were testing.

It could be an integration test, or it could be component testing for parameter verification. (like thrust power or oscillation or fuel geometry)

Even if it were an integration test, it's still a test. It may be projected flight hardware but it is not ready flight hardware.

That's going to change the picture [of the test] quite a bit.

Does it mean a solid can fail? Sure. Does it change the overall picture? I seriously doubt it, that's why they do "loss of crew" studies.

publiusr
2009-Aug-28, 07:38 PM
Solids are pretty reliable but when they do fail, they fail spectacularly. So much so, the Air Force has assessed that if Ares I (http://www.nasawatch.com/archives/2009/07/usaf_orion_crew.html) failed early in the flight, the crew will be killed. They based this study on the failure of a Titan IV SRB back in 1998. The analysis result is that the Orion launch escape system wouldn't be able to get the crew clear of the raining debris. Nylon parachutes don't like raining debris. Here's a video of a Delta II failure (http://www.youtube.com/watch?v=WsVzpE7ltb8) caused by an solid that exploded. Such failures are rare but they do happen from time to time.

Several things can cause a large solid rocket motor to fail. Two of the more common failure causes are insulation separation and propellant cracks. Insulation separation allows the hot combustion gases to come in contact with the casing wall. This can cause more propellant to ignite prematurely. Propellant cracks cause more propellant surface area than intended to be exposed for combustion, resulting in higher pressure inside the casing. In either case, the resulting explosion is usually spectacular.

Also understand that a Delta II's solids are really not as strongly built as the SRB casings. The O-ring problem has been fixed. Ironically, the Challenger disaster showed just how rugged those solids are by surviving the ET rupture and continuing on like nothing even happened. No violent debris spewing explosion, even when the range safety officer triggered the RSS-- -this after almost flying sideways--not exactly good for 'chasing a capsule.'

A lot of this is just religion:

Solids vs liquids
pump-fed vs. pressure-fed
side mount vs top mount
winged vs ballistic
manned vs unmanned
--and so on and so forth

Nicolas
2009-Aug-28, 08:23 PM
Well.. I'd expect them to use used modules for a test like this

Well...one of the segments flew on STS-1...Tad bit "used". :)

Larry Jacks
2009-Aug-28, 08:48 PM
A lot of this is just religion:

Solids vs liquids
pump-fed vs. pressure-fed
side mount vs top mount
winged vs ballistic
manned vs unmanned
--and so on and so forth

Not quite.

Solids verses liquids has a lot of engineering basis behind the arguments. Solids are simple, mostly reliable, and relatively inexpensive. Liquids offer higher performance in the form of specific impulse.

Pressure -ed verses pump-fed also has engineering basis. A pressure fed system is simplier and less expensive, plus turbopumps are a source of failure. However, a pressure fed system has to be able to withstand tank pressures higher than the engine chamber pressure while the tanks for a turbopump system can be much lighter. Even a relatively modest rocket engine can have a chamber pressure of 300 PSI. Building tanks to withstand 300+ PSI makes for some heavy tanks. I find it interesting that SpaceX choose a pressurized tank design for the upper stage of their Falcon 1 booster. Off hand, I don't know of any other boosters with that design feature (including the Falcon 9).

Side mount verses top mount also has engineering concerns. The Shuttle C choose side mount because the engines would be in the same relative location as the Shuttle Orbiter, meaning it wouldn't need any changes to the launch pad infrastructure. It's also possible that a side mount would offer greater flexibility in payload geometry than a top mount. It's also possible that a top mount layout would offer some structural advantages - a significant engineering concern.

Winged vs ballistic - well, how many winged boosters have ever been developed? Pegasus? Any others? Perhaps there are engineering reasons why this is so, or do you simply dismiss that as "religion"?

Manned vs unmanned - each has its place in a comprohensive space program. Those who argue "either-or" on this or most other issues are setting up a false dicotomy.

Nicolas
2009-Aug-28, 08:51 PM
versus.
I agree with the sentiment of your post. It's not "like religion" if you've got objective engineering arguments for a choice.

publiusr
2009-Aug-28, 09:04 PM
It also depends on what you want to do. India keeps liquid fueld strap-ons to a solid first stage. Now from a structural point of view that makes sense. Yet it is actually better to have (big) solid strap-ons fall away more quickly due to their rugged, heavy design, and keep a lightweight core that is quickly staging its liquid propellant load as thrust--getting lighter all the time.

And Engineers do have their disagreements. Korolov and Glushko got hot over propellant choice--and both had good arguements.

mugaliens
2009-Aug-29, 11:24 PM
A lot of this is just religion:

...

manned vs unmanned...

Very good response, Larry, so I'll not retread it, except to say that Ares is currently an unmanned program as it's engines, the RS-68 (http://en.wikipedia.org/wiki/RS-68), are not human-rated (http://en.wikipedia.org/wiki/Human-rating_certification). As the RS-68 was developed for the unmanned heavy-lift Delta IV program, it will require more than 200 design changes to the RS-68 engines before they're certified to meet human-rating standards.

Earlier somone had mentioned the strength of the Shuttle's SRBs continuing to fly long (37 seconds) after the ET and Shuttle explosively disintegrated around them, and that is indeed true. Part of the reason as to why they're so sturdy is that they were designed to be reusable (http://www.youtube.com/watch?v=2HOsc7r7BiQ), unlike the external tank (http://www.youtube.com/watch?v=0hwjE1fp-RM&feature=related). One of the SRBs which flew in STS-1 has flown 48 times over thirty years! Unlike most SRBs, which have a 1% failure rate, almost always due to over-pressure causing catastrophic case failure, the SRBs are over-designed to never fail.

This video (http://www.youtube.com/watch?v=wNsJUmFrUCA&feature=fvw)shows, rather spectacularly, what usually happens when things go wrong. Most of the explosions in the video are liquid fueled, but some are solids.

The Challenger disaster, by contrast, demonstrated that the SRBs, despite their faulty o-ring design, were made of some very tough stuff.

ugordan
2009-Aug-30, 11:39 AM
I find it interesting that SpaceX choose a pressurized tank design for the upper stage of their Falcon 1 booster. Off hand, I don't know of any other boosters with that design feature (including the Falcon 9).
Not really that uncommon for smaller vehicles. As 2nd stages effectively operate in vacuum (you don't need high pressures for the chamber) and their tank volume is small, it simplifies an engine greatly.

BTW, Delta II second stage is also pressure-fed.

RGClark
2009-Aug-30, 03:43 PM
Steve Cook, Ares program manager, has chosen to resign:

NASA MSFC Internal Memo: Steve Cook Resignation.
STATUS REPORT
Date Released: Thursday, August 27, 2009
Source: National Aeronautics and Space Administration
http://www.spaceref.com/news/viewsr.html?pid=32169


Bob Clark

Glom
2009-Aug-30, 05:28 PM
Side mount verses top mount also has engineering concerns. The Shuttle C choose side mount because the engines would be in the same relative location as the Shuttle Orbiter, meaning it wouldn't need any changes to the launch pad infrastructure. It's also possible that a side mount would offer greater flexibility in payload geometry than a top mount. It's also possible that a top mount layout would offer some structural advantages - a significant engineering concern.

Would a side mount offer geometry flexibility? Unless you really wanted something to stick way out at the side, it would seem sticking it on the top would allow it to be bigger.

ugordan
2009-Aug-30, 06:17 PM
It's also possible that a side mount would offer greater flexibility in payload geometry than a top mount.
I'm not sure that would be the case. Any payload geometry would be limited by fairing size and an inline version would win over (not)shuttle-C there, hands down. I also hear not-shuttle-C could have further limitations on payload center of gravity due to controllability issues, but this is something that would require additional analysis.

Larry Jacks
2009-Aug-30, 07:38 PM
Regarding the potential design flexibility, I was thinking of the Energyia design. The same arrangement of large propellant tanks with RD-170 engines at the bottom and essentially 4 Zenit strap-ons meant they could switch from an unmanned payload to a Buran relatively easy. The orbital portion only had to carry the equivalent of the OMS engines to inject the payload into orbit. It was a very flexible and cleaver design.

Stacking the payload on top of the tank might prove less flexible. No matter how huge the fairing is (and it'd be very big), that will always be a design limitation when it comes to payload size. It might also be a factor with payload mass. It seems designing different sized fairings to accommodate payload differences for a side mount would be less difficult than for a top mount. That may not be true in practice, though.

ugordan
2009-Aug-30, 07:53 PM
Note the sidemount has limits on fairing size being close to the ET and all. For example, you couldn't fit the proposed Altair lander in a sidemount. The controllability problem for bigger fairings on a sidemount arises because you're moving the center of payload cannister away from the ET and the SSMEs can gimbal out only so much. Sticking the payload on top of a vehicle poses no such problems. Controllability-wise, it's the best option as it minimizes aerodynamic drag (hence helps performance too) and lessens requirements on main engine gimbal capability. I think Direct folks at one point even suggested removing the TVC from the SRBs altogether because the inline engines would have enough control authority even without them - something not possible with shuttle-type sidemount.

publiusr
2009-Sep-01, 12:28 AM
For example, you couldn't fit the proposed Altair lander in a sidemount. The controllability problem for bigger fairings on a sidemount arises because you're moving the center of payload cannister away from the ET and the SSMEs can gimbal out only so much. Sticking the payload on top of a vehicle poses no such problems. Controllability-wise, it's the best option as it minimizes aerodynamic drag (hence helps performance too) and lessens requirements on main engine gimbal capability.

Those are very good points.




Part of the reason as to why they're so sturdy is that they were designed to be reusable (http://www.youtube.com/watch?v=2HOsc7r7BiQ), unlike the external tank (http://www.youtube.com/watch?v=0hwjE1fp-RM&feature=related). One of the SRBs which flew in STS-1 has flown 48 times over thirty years! Unlike most SRBs, which have a 1% failure rate, almost always due to over-pressure causing catastrophic case failure, the SRBs are over-designed to never fail.

This video (http://www.youtube.com/watch?v=wNsJUmFrUCA&feature=fvw)shows, rather spectacularly, what usually happens when things go wrong. Most of the explosions in the video are liquid fueled, but some are solids.

The Challenger disaster, by contrast, demonstrated that the SRBs, despite their faulty o-ring design, were made of some very tough stuff.

And that is all that I was getting at. The folks at Direct, by the way do use existing SRBs, as will any Ares V lite, or Magnum, etc.

What this solid vs liquid discussion is omitting is why solids are used to begin with--to augment liquids that otherwise not be able to get off the ground on their own with full propellant tanks. Saturn V had no such problems, but there have been liquids without so much thrust--and without solids to help them along, may pose a threat to their own pads.

samkent
2009-Sep-01, 07:31 PM
Well they have eliminated the Ares test rocket hardware and software as the reason for the delayed test. It looks like the ground hardware was at fault.

I reiterate my original statement that solids do not give as many potential reasons to delay launches. Which will make them a better choice for launch vehicles.

Larry Jacks
2009-Sep-01, 08:07 PM
Launch delays is only one criteria for judging whether solids or liquids make better boosters. The military uses solid rocket motors in missiles so reliability and rapid launch rank very high. However, when it comes to putting payload into orbit, over 50 years of booster development shows that solids are more suitable for augmenting the thrust of liquid fueled rockets. Solids are simple, reliable, and relatively inexpensive but their lower performance (primarily in terms of specific impulse) is the reason why no one has built even a medium payload space booster using only solid rocket motors. For a viable space booster, payload to orbit for a given price favors liquid fueled rockets. Launch delays, while annoying and sometimes expensive, are a lessor concern.

ugordan
2009-Sep-04, 05:12 PM
Via NSF.com comes a presentation that's of relevance here, dates back to 2005 and it's been posted on the Augustine Commission papers page:

Crew Survival Office’s Position on the Acceptability of the Proposed Inline RSRB Launch Vehicle for Crewed Launches (http://www.nasa.gov/ppt/382364main_46%20-%2020090802.6.CSO%20inline%20concerns.ppt) (ppt, 1MB) - Submitted by Leo Langston, Paul Porter, Clint Thornton, JSC Crew Survival


In 44 years of human space flight no flight crew has been lost during ascent as the result of a totally liquid based launch vehicle

- Anticipated failures and robust ascent abort system
- Two loss of vehicle events in the manned Soyuz program ended in successful launch aborts

Soyuz 18-1 – 2nd/3rd staging separation failure
Soyuz T 10-1 – GSE failure; pad fire


However, in 24 years of flight on SRB based systems one flight crew has been lost as the result of an SRB failure during ascent

Unexpected and unanticipated failures, and no valid abort system
STS 51L



“It appears that there are enormous differences of opinion as to the probability of a failure with loss of vehicle and of human life. The estimates range from roughly 1 in 100 to 1 in 100,000. The higher figures come from the working engineers, and the very low figures from management. What are the causes and consequences of this lack of agreement? Since 1 part in 100,000 would imply that one could put a Shuttle up each day for 300 years expecting to lose only one, we could properly ask "What is the cause of management's fantastic faith in the machinery?"

- R. P. Feynmann, Personal observations on the reliability of the Shuttle, Report of the Presidential Commission on the Space Shuttle Challenger Accident, Appendix F

Nicolas
2009-Sep-04, 05:17 PM
The engineers are and feel liable for the machinery they come up with. Liability makes you realistic. 1 in 100,000 is a bit, erm, gaga.

As for the other statistic: 1 and 2 aren't really the kind of values you can do loads of statistics on, but anyway. I conclude from these that the lack of a launch abort system is more of an issue than the launcher technology. Though I don't know whether a LAS would have been of much use for STS-51; were they still alive just after the ET blew up?

Not that Challenger is 100% relevant for designs without an ET, but with the limited statistics on spaceflight available, it's all we have available.

ugordan
2009-Sep-04, 05:23 PM
As for the other statistic: 1 and 2 aren't really the kind of values you can do loads of statistics on, but anyway. I conclude from these that the lack of a launch abort system is more of an issue than the launcher technology.
Have you actually bothered to look at the document or are you simply drawing conclusions from a single snipped I extracted?

Nicolas
2009-Sep-04, 05:38 PM
I completely read through it, thank you. I know there's lots more in the document than what I type I meant the other statistic in your post. But my point is that, looking at everything available, lack of crew escape system appears to me to be a larger issue than the launcher technology used.

My main argument for this is that the shuttle design SRB is very sturdy and does not appear to (commonly) have these immediate rupture failures for which a LAS doesn't have any time to react, removing that disadvantage compared to liquid failures. In case of STS-51 the failure still was immediate (the Et blowing up) but this is no longer relevant for the single SRB stick design.

Larry Jacks
2009-Sep-04, 08:41 PM
Though I don't know whether a LAS would have been of much use for STS-51; were they still alive just after the ET blew up?

Yes, there is evidence the crew survived the explosion (http://www.snopes.com/horrors/gruesome/challenger.asp). In the wreckage, there were some manually activated air packs that were turned on. The actual acceleration forces weren't that great during the explosion, certainly not as bad as it initally appeared.

When the Challenger stack exploded, the Shuttle had a significant vertical velocity component. From memory, Challenger exploded at about 40,000 feet altitude. Estimates are that the crew compartment continued to climb to over 60,000 feet. At that altitude and with the crew compartment probably depressurized, the crew would've passed out. They were wearing little more than jump suits with a helmet (http://encarta.msn.com/media_461529240/challenger_crew_heads_to_launch_pad.html). To stay alive much above 40,000 feet, you need external pressure on your body. The crew compartment impacted the ocean about 4 minutes after the explosion with an estimated deceleration of over 200 Gs. It's unlikely any of the crew were awake to see it coming and death was instant.

ugordan
2009-Sep-04, 11:00 PM
Challenger didn't explode, it structurally broke up and the external tank breakup caused just a large deflagration with virtually no shockwave. Hollywood-style "explosion", not a real blast. To put it another way, the ET didn't destroy the orbiter, aerodynamic forces did - there goes that infamous letter q again.

Antice
2009-Sep-05, 05:45 AM
If the leak had been detected the orbiter could have aborted. but nobody was looking for such a failure back then. apart from maybe one guy. and he wasn't being listened to.

joema
2009-Sep-05, 09:27 AM
If the leak had been detected the orbiter could have aborted...
There was no abort possible. The orbiter could not detach from the stack while the SRBs were burning.

Had a launch escape system existed, it might have saved them. However that depends on the design of that hypothetical system.

zerocold
2009-Sep-05, 10:05 AM
Which system suffers from more vibration, solid fuel rockets or liquid fuel ones?

Thanks

ugordan
2009-Sep-05, 11:24 AM
Which system suffers from more vibration, solid fuel rockets or liquid fuel ones?

A quick look at solid vs. liquid vehicle user guides answers that. Solids are more rough, by a long shot. Payloads designed for solid launch vehicles (especially larger ones) need to be more rugged or vibration isolation mechanisms need to be added to the payload adapter.

Antice
2009-Sep-05, 12:40 PM
Vibration issues are directly linked to thrust. it's not that solids vibrate more. it's that they generally has a LOT more thrust compared to mass.
I mean. what roars louder. a 90 HP car engine or a 250 HP car engine.
while engines can be noisy they aren't generally making enough acoustic vibration to destroy anything.... a rocket engine OTOH.......

ugordan
2009-Sep-05, 02:24 PM
Vibration issues are directly linked to thrust. it's not that solids vibrate more. it's that they generally has a LOT more thrust compared to mass.

No. A liquid launcher with the same payload and thrust as a solid launcher will have a less harsh ride. It's not acoustic environment, that's similar for both launcher types, it's vibration dynamic environment, fast G load variations on ascent.

E.g. the effect is likened to riding on a jackhammer. That is not an acoustic issue. You can wear earplugs and still have your guts ripped apart.

On the other hand, purely acoustic environments for both launch vehicle types have little to do with engine type. They max out:
immediately at liftoff where exhaust supersonic shockwaves bounce back from the ground to the payload. This can be somewhat alleviated by water sound suppression systems.

around max-Q where the supersonic airflow causes loud noises inside the fairing. The higher the max-Q, the louder the acoustics. Typically, solid vehicles have higher max-Q environments, but all other things equal the environments are similar. These acoustics are alleviated by acoustic blankets inside the payload fairing, if necessary.

joema
2009-Sep-05, 03:20 PM
Vibration issues are directly linked to thrust. it's not that solids vibrate more. it's that they generally has a LOT more thrust compared to mass....
That's not the case. E.g, the Saturn V and shuttle have very roughly similar liftoff thrust.

However the Saturn V had much less vibration. See the below chart of S-IC longitudinal acceleration from Apollo 11.

I don't have the similar chart from a shuttle launch, but I'm certain it's a lot more. There are various cockpit videos showing the shuttle astronauts being jostled around considerably during stage 1 ascent.

samkent
2009-Sep-05, 03:22 PM
I thought there was no about while the SRBs were fireing???

ugordan
2009-Sep-05, 04:06 PM
There are various cockpit videos showing the shuttle astronauts being jostled around considerably during stage 1 ascent.
Saturn V also threw astronauts around sideways pretty vigorously during 1st stage boost, but it was due to the guidance system and engine gimbaling. I suspect the same is true for Shuttle launches and that's what you see in those videos.

What you don't see in cockpit footage are these longitudinal acceleration vibrations we're talking about here (which for the most part are responsible for shaky voices of the astronauts during liftoff).

The chart you posted does show what we're talking about, and this is where solids are much more harsh. Not necessarily in the shuttle configuration where the ET intertank damps the vibrations, but certainly for inline vehicles.

Nicolas
2009-Sep-05, 07:07 PM
In case of the shuttle, is it mainly the ET (its inertia, the connectors, or ...?) that dampens the vibrations or rather the fact that 2 SRB's burn simultaneously and hence average out the vibrations a bit? Or are both effects of about equal importance?

In the same spirit, was Sat5 less shaky because of using 5 engines at the same time?

ugordan
2009-Sep-05, 07:29 PM
In case of the shuttle, is it mainly the ET (its inertia, the connectors, or ...?) that dampens the vibrations or rather the fact that 2 SRB's burn simultaneously and hence average out the vibrations a bit? Or are both effects of about equal importance?

Both. Also, a tank full of liquid propellant helps act as a damper.



In the same spirit, was Sat5 less shaky because of using 5 engines at the same time?
Theoretically, yes since multiple random vibrations have an equal probability of interfering with each other as they do of adding up their waveforms. So 5 smaller vibrations is not the same as one big one, 5x the size. Although, if you're not careful to make sure the 2nd case (constructive adding of waveforms) doesn't happen, you can get resonance and things like pogo which did occur on some Saturn V flights and needed to be mitigated.

Today, both pogo and solid motor oscillations are well understood and pogo is inherently easier to get rid of because you damp vibrations at the engine-feedline/tank interface and liquid propellants are inherently good at damping vibrations. Solid motors vibrate as a whole, and that's a huge volume and a lot of energy.

Nicolas
2009-Sep-05, 07:36 PM
Clear explanation, thanks.

zerocold
2009-Sep-06, 02:03 AM
joema, that is a very interesting graphic, great contibution, thanks.

Wonder if the vibration load increment at the end of the stage burst is something normal for all rockets, and have something to do with the exhaust pressure changes

BTW, is that data taken from static tests, or from flight tests?

How have been the advances on solid fuel propelants?, space programs are stuck on LOX engines for manned missions, i don't have data about solid propelents, the fuel for solid rockets has evolved?, and which have better perspective for the future, i think liquid fuel based rockest are stuck already, and i don't expect great improvements in the future.

Nicolas
2009-Sep-06, 11:48 AM
(many) Liquid fueled rockets use the second most energetic mixture (LO2 + LH2). The most energetic mixture is an environmentally naaaaasty thing, that's why. LO2 + LH2 is quite clean on top of that (if produced clean, of course). Of course there's also other mixtures being used.

As for solids, I don't really know. Rutan uses a rubber compound. The SRB's aluminum and other stuff. In both cases not too clean. I don't know about the energy content and possible improvements therein. Having a larger Isp at the same huge thrust levels would be very nice.

ugordan
2009-Sep-06, 12:04 PM
Wonder if the vibration load increment at the end of the stage burst is something normal for all rockets, and have something to do with the exhaust pressure changes

The engines vibrate pretty much the same way the entire time, but the mass of the entire vehicle and its natural frequency keeps changing throughout the flight. The areas of higher vibrations are areas where vehicle's natural longitudinal frequency is more susceptible to being excited by those vibrations - note that frequency is slowly increasing and sweeping across a certain range. If your design doesn't make sure the vehicle's own frequency is outside this range, you can get pogo.

I'm thinking this peak on Apollo 11 occured at roughly the same time as strong pogo on Apollo 6 occured so in a way you can see the effect of the "shock absorbers" installed on subsequent Saturn V vehicle.

djellison
2009-Sep-06, 03:46 PM
I thought there was no about while the SRBs were fireing???

What?

joema
2009-Sep-06, 05:55 PM
What?
I think he meant "no abort".

In actual practice, aborts may be selected while the SRBs are firing, but they aren't implemented until the SRBs separate. That's typically done by selecting the abort mode with a rotary switch (RTLS, TAL, ATO, AOA), but the computers take no trajectory deviations until after SRB separation.

After Challenger a "fast separation" mode was added which in theory allows the orbiter to separate from the stack in a few seconds (vs 15-20 sec normally). However studies show it's not usable during SRB flight -- the orbiter would hang up on the attach points.

Nicolas
2009-Sep-06, 06:31 PM
And if it wouldn't, it would drop back down like a brick. That would require 7 lightning fast astronauts to all make it out on their chutes in time.

And then I haven't even considered the possibly heavily tumbling craft they'd have to move through and open the hatch...

mugaliens
2009-Sep-06, 08:07 PM
There was no abort possible. The orbiter could not detach from the stack while the SRBs were burning.

Had a launch escape system existed, it might have saved them. However that depends on the design of that hypothetical system.

Shuttle Orbiter weight: 151,205 - 240,000 lbs
Payload: 53,600 lb
Total: 204,805 - 293,600 lb

Engine Thrust (combined): 1,181,400 lb

Acceleration: 4.0 - 5.8 g

However, since the SSME's are throttleable down to 67%, the lower end of the thrust is 791,538 lb, for accelerations ranging from 2.68 to 3.9 g, depending on payload.

The problem is that the SSMEs are tied to the external tank and cannot use fuel internal to the orbiter. However, for the full second it would take to initial an emergency separation, the fuel in the lines internal to the orbiter could keep up with the booster-driven external tank in terms of acceleration.

Joema: What's the mass of the external tank with it's remaining fuel immediately prior to SRB separation? Combined with the SRB empty mass and peak thrust, this would give us an approximate acceleration of the SRB-driven external tank combination.

My point: Regardless of whether the shuttle has a landing field available, I believe it would have been possible to design a computer-driven separation from the stack during SRB-driven ascent using maneuvering thrusters, shuttle elevons, and possibly the maneuvering engines. Yes, a lot of safety protocols would have to be bypassed in less than a second, but with computer control, I believe it would have been possible to safely separate from the stack into a 2G pull-away, under computer control, before maneuvering into a glide attitude capable of:

1. Return to KSC.

2. Stable platform for escape via the post-Challenger system that was developed.

3. Transferring control to Shuttle pilot in command for ditching.

The exhaustion of remaining fuel in the orbiter's internal lines for the SSMEs would add energy/altitude. The post-separation firing of the maneuvering engines to fuel exhaustion would add energy/altitude while reducing/eliminating the explosive fuel on board. Simultaneous firing of all attitude thrusters would reduce/eliminate the highly toxic hypergolics on board. All of these actions would lighten the load considerably, allowing for a safer touchdown/ditching speed.

Thus, I believe it would have been possible to design this into the Shuttle's capabilities, and may yet be possible to redesign the computer controls to make it possible using existing hardware. It wasn't, however, as all Space Shuttle components were man-rated to the strictest of standards, and it was thought that it would be unnecessary.


Vibration issues are directly linked to thrust. it's not that solids vibrate more. it's that they generally has a LOT more thrust compared to mass.

While there is certainly a proportionality between thrust and vibration, given an equal amount of thrust, solids are considerably more turbulent due to the simple fact that their combustion occurs along the entire length of the inside of their fuel propellant, whereas in the SSME's, gaseous hydrogen fresh from the hot-gas manifold cooling system mixes with liquid oxygen in the combustion chamber, which sits atop the expansion nozzle. The latter process produces considerably less vibrational energy per pound of thrust than the SRBs.

The Jim
2009-Sep-20, 11:57 AM
What about construction time?

I can’t find the lead time for an SRB. At one point I did read that traditional booster ‘X’ required 18 months from signing to delivery. I don’t remember which booster it was, but I’m almost certain it wasn’t a manned booster.

From my limited viewpoint, I see production of SRB segments as much easier than the liquid counter parts. Therefore allowing the ability to slip an extra launch into the schedule if required for say emergency evacuation of an injured person on the ISS.

Limited is right. You are ignoring the upperstage and spacecraft production leadtime.

The Jim
2009-Sep-20, 11:59 AM
Funny how the term 'reliability considerations' keeps popping up with liquids.

Out of the 254 SRBs used in the US manned program…

Zero launch delays due to a SRB problem.
Zero failures to ignite when commanded.
Zero in flight shut downs.
Zero SRB explosions.

On the other hand, the liquid side of the equation has caused more launch delays than I can count. Even the first launch after Columbia was delayed for two weeks due to fuel sensor problems.


You have omitted delays due to HPU failures, roll backs for booster replacements, Challenger, delays for extended booster checkout, etc

The Jim
2009-Sep-20, 12:02 PM
1. Ask any project manager and they will tell you that saving millions of dollars is a huge savings. Plus look at the scale back of infrastructure. Check out the Taurus launch vehicle.

2. They are coming and I predict in a decade the majority of first stages will be solid.

1. you are ignoring the huge solid motor production infrastructure. Also the large amount of infrastructure at the launch site. Taurus is an exception and not the rule.

2. You have nothing to base that on and you could not be more wrong. Ares I is a exception and not the rule.

The Jim
2009-Sep-20, 12:06 PM
SpaceX had to salt water certify their engines in order to use the Kwajalein launch site.
that island is nothing more than a pile of sand far out on the ocean after all.
They should not degrade noticeably by being immersed in salt water during recovery.
to be fair. they paid a lot to learn that they needed to proof their rocket against salt corrosion by having their first launch fail like that.


Incorrect. Spacex did not "salt water certify" their engines. They have not "proofed" their rocket again salt corrosion. They did some minor fastener changes after the first launch.

There will be issues with avionics and wiring after immersion in salt water.

The Jim
2009-Sep-20, 12:13 PM
I reiterate my original statement that solids do not give as many potential reasons to delay launches. Which will make them a better choice for launch vehicles.

Wrong and unfounded. SRB have caused delays. There still arevthe upperstages.

Also most of the shuttle delays are due to weather or the spacecraft part of the orbiter.

The Jim
2009-Sep-20, 12:14 PM
The Challenger disaster, by contrast, demonstrated that the SRBs, despite their faulty o-ring design, were made of some very tough stuff.

incorrect. See Titan IV-A20

The Jim
2009-Sep-20, 12:17 PM
Also understand that a Delta II's solids are really not as strongly built as the SRB casings. The O-ring problem has been fixed. Ironically, the Challenger disaster showed just how rugged those solids are by surviving the ET rupture and continuing on like nothing even happened. No violent debris spewing explosion, even when the range safety officer triggered the RSS-- -this after almost flying sideways--not exactly good for 'chasing a capsule.'


Incorrect, they were almost empty of propellant. See Titan IV-A20 for what happens when SRMs open up.

The Challenger SRB's went different direction because of the way they were detached from the ET. The Ares I SRM will chase a capsule.

The Jim
2009-Sep-20, 12:19 PM
Launch delays is only one criteria for judging whether solids or liquids make better boosters. The military uses solid rocket motors in missiles so reliability and rapid launch rank very high.

The military does not rank reliability so high. Weapon systems have lower reliability than space systems.

Response time and long term storage is the main reason for solids.

The Jim
2009-Sep-20, 12:38 PM
1. My point: Regardless of whether the shuttle has a landing field available, I believe it would have been possible to design a computer-driven separation from the stack during SRB-driven ascent using maneuvering thrusters, shuttle elevons, and possibly the maneuvering engines. Yes, a lot of safety protocols would have to be bypassed in less than a second, but with computer control, I believe it would have been possible to safely separate from the stack into a 2G pull-away, under computer control, before maneuvering into a glide attitude capable of:


2. The exhaustion of remaining fuel in the orbiter's internal lines for the SSMEs would add energy/altitude. The post-separation firing of the maneuvering engines to fuel exhaustion would add energy/altitude while reducing/eliminating the explosive fuel on board. Simultaneous firing of all attitude thrusters would reduce/eliminate the highly toxic hypergolics on board. All of these actions would lighten the load considerably, allowing for a safer touchdown/ditching speed.



1. Totally nonviable and not possible. The thrusting of the SRB would have still hung up the aft attach points. The total thrust (a few thousands of pounds) of the RCS is trival compared to the loads imparted by the SRBs. There is a minimum altitude for the OMS engines to fire.
The elevons would be of no help. A. up deflection would make the problem worse by pitching up the orbiter, which is the problem in the first place
B. down deflection pushes the orbiter into the ET

2. Not viable. The propellant depletion sensors are in the ET and not the orbiter to give the engines the time to shut down since the flow rates are so high. Just like Challenger, the engines would go into ox rich shutdown (fires) and have the turbopumps go into overspeed (spin apart) since they are unloaded.

OMS engines can't fire below a certain altitude (in the 100k's) and they are only 12k total thrust which isn't enough to do anything.

The forward attitude thrusters can be fired at the low altitude either

samkent
2009-Sep-20, 02:16 PM
Quote:
Originally Posted by samkent

I reiterate my original statement that solids do not give as many potential reasons to delay launches. Which will make them a better choice for launch vehicles.
Wrong and unfounded. SRB have caused delays. There still arevthe upperstages.

Also most of the shuttle delays are due to weather or the spacecraft part of the orbiter.

You misread my statement. Upper stages, weather and orbiter problems are not the fault of the SRB. Besides many of the orbiter delays have been due to the engines contained within the orbiter. I stand by my statement.


Quote:
Originally Posted by mugaliens

The Challenger disaster, by contrast, demonstrated that the SRBs, despite their faulty o-ring design, were made of some very tough stuff.

incorrect. See Titan IV-A20

Incorrect conclusion. See below concerning the Titan IV-A20 accident.

http://www.globalsecurity.org/space/library/report/1999/titan_iv-20_sum.htm


Total vehicle weight at liftoff was just over 1.9 million pounds. The vehicle ascended as predicted, except that 20 feet of the Turbopump Assembly (TPA) drainline did not release at liftoff. The drainline is ½ inch diameter plastic tubing. Except for the TPA drainline, the vehicle performed as expected until T+39.416 seconds. At this point, a series of anomalous electrical power and guidance subsystem events occurred which resulted in maximum steering commands being issued to the SRM TVC system. These commands placed the launch vehicle in an angle of attack which exceeded structural limits and caused the aerodynamic breakup of the vehicle.
The overall sequence of anomalous events are as follows:
• Beginning at T+39.416 seconds, a series of intermittent electrical shorts caused power fluctuations to occur within the VPS.
• At T+39.463 seconds, an alarm was issued indicating that voltage to the MGC had fallen below the 21.8 volt threshold. When input voltage to the MGC drops below 21.8 volts, an internal interrupt is generated that starts a power down sequence of the MGC. The power down causes the MGC to stop sending timing reference signals to the IMU. Loss of this signal to the IMU caused a loss of gimbal torque motor control. This led to an uncontrolled physical motion of the inertial platform and loss of the inertial reference frame.
• At T+39.650 seconds, the MGC recovered power and reinitiated the timing reference signal to the IMU. The IMU then presented a false indication to the MGC that the vehicle had pitched up approximately 26 degrees and yawed left 5 degrees from its planned attitude.
• At T+39.818 seconds, in an attempt to compensate for these perceived changes in vehicle attitude, the MGC control system commanded the vehicle into a full pitch down and yaw right.
• When the vehicle's pitch angle reached approximately 13 degrees off planned trajectory, aerodynamic stresses on the launch vehicle exceeded its structural design limits.
• At T +41.545 seconds, SRM No. 1 (the north SRM) separated from the core vehicle, triggering the Inadvertent Separation Destruct System (ISDS) of that SRM. That explosion impacted the core vehicle causing its destruction.

Now what part of that was sue to the SRB?


The military does not rank reliability so high. Weapon systems have lower reliability than space systems.

Which military is it that doesn’t rank reliability at the top of their list?


Response time and long term storage is the main reason for solids.

Good reasons to use them for space systems.

ugordan
2009-Sep-20, 02:52 PM
Besides many of the orbiter delays have been due to the engines contained within the orbiter. I stand by my statement.

OK, allow me to twist the argument this way: how many SSME problems in the history of the shuttle program (and do note there are 3 SSMEs flying on each flight that flies 2 SRBs) have caused crew fatalities? Now, how many SRB problems have caused crew fatalities?

By your opinion the fewer-delay argument is worth that price? Curious.



Now what part of that was sue to the SRB?

Not on Titan IV A-20, but nevertheless an earlier (http://www.fas.org/spp/military/program/launch/titan.htm) Titan IV:

A Titan IV vehicle launched from VAFB on 2 August 1993 experienced a failure. The subsequent investigation indicated that a burn through on one of the SRMs caused the failure.

Q.E.D.

In fact, of all the immediately catastrophic U.S. launch vehicle failures in recent history, AFAIK all were caused by SRBs - Titan 34D in 1986, Titan IV in 1993 and Delta II in 1997. You can argue quality assurance on human rated vehicles will make SRBs more reliable, but the same argument holds for their liquid engine counterparts so that argument is moot.



Which military is it that doesn’t rank reliability at the top of their list?

You can argue as long as you want, but "human rated" levels of reliability are not on top of their list. Cost, ease of use, robustness etc. are more important. You think the military would care if 1 out of 10 ICBMs failed in flight in case of an all-out engagement?



Good reasons to use them for space systems.
For humans not good enough. Humans take reliability and safety over response time and storage life.

The Jim
2009-Sep-20, 03:15 PM
1. I stand by my statement.

2. Upper stages, weather and orbiter problems are not the fault of the SRB.

3. Incorrect conclusion. See below concerning the Titan IV-A20 accident.
Now what part of that was sue to the SRB?
4. Which military is it that doesn’t rank reliability at the top of their list?
5. Good reasons to use them for space systems.


1. It is still not a valid reason to rank solids over liquids. Do you work in the spaceflight business? No, so your opinion carries no weight.

Intermediate to large Launch vehicle have moving away from solid first stages. Titan IV was retired. Delta IV, Atlas V, Falcon 9, Ariane 6, Angara, etc do not use solid first stages. Ares I is an anomaly.

2. A vehicle with a solid first stage would still have to contend with them and therefore no net benefit and actually, it would be a net loss of benefits from the low ISP.

3. Your conclusion is incorrect. the Titan IV-A20 accident demonstrates why solids are bad. Failures unrelated to the SRMs require the SRM to be blown up with bad results. Also the Challenger SRB was out of family. SRMs blow up without warning, that is the standard, (see Delta II, Titan 34D, Titan IV, etc)

4. Military rockets don't require the reliability standards of space launch vehicle. The other requirements are more important. (do your research).

5. Nope, those are not requirements for space launch, and actually space launch solid don't like long term storage. Also for quick response, there is no such thing for standard space launch.

So next time, do your research and know something before posting and don't post incorrect data.

samkent
2009-Sep-20, 07:11 PM
Your conclusion is incorrect. the Titan IV-A20 accident demonstrates why solids are bad. Failures unrelated to the SRMs require the SRM to be blown up with bad results.

So are you saying they wouldn’t blow up a liquid if it vered off track??

Titan 34D- If you are referring to the 1985 launch, it was a propellant leak that shut down the liquids after launch. Are the results of blowing a liquid some how“not bad”?


So next time, do your research and know something before posting and don't post incorrect data.

I do my research as I find the time and need. I do include links to items I feel relevant. So I feel I “know something” and I’ll post as I chose. Feel free to include links to backup your points.


Not on Titan IV A-20, but nevertheless an earlier Titan IV:

I read your link and I counted 4 failures in total. 2 solid and 2 liquid.


A Titan IV vehicle launched from VAFB on 2 August 1993 experienced a failure. The subsequent investigation indicated that a burn through on one of the SRMs caused the failure. Corrective actions were implemented to allow launch operations to resume in February 1994.

Six months to correct, sounds quick enough to me. How many years was it for the shuttle?

And


After extensive analysis, it was determined that the failure resulted from a design flaw in the solid propellant grain, causing a critical failure where the solid rocket motor segments are joined. After extensive modelling, the grain was redesigned and the problem corrected.

Sounds like a permanent fix to me with no chance of reoccurrence. Those are the best kind of fixes.

On the liquid side of the equation.


The August 1992 AC-71 duplicated the April 1991 AC-70 failure, even though the cause had been thought corrected. In both cases the C-1 engine turbopump failed to rotate and allow the engine to bootstrap, though in both cases both engines ignited properly.

I suspect there are a dozen other ways that a turbo pump could fail. Each with a resulting boom! Now how many other failure points are there to liquids??

ugordan
2009-Sep-20, 07:59 PM
So are you saying they wouldn’t blow up a liquid if it vered off track??

No, he's saying:
1) such range safety actions aren't instantaneous while SRB case rupture is
2) Upon range safety action, liquid vehicles shutdown engines and propellants are dispersed in basically a large fireball. Solid "unzipping" results in a hail of flaming fragments that keep going on the same trajectory the vehicle is going, posing a threat for a manned capsule above. Case in point - the Challenger ET "explosion" didn't destroy the orbiter, but aerodynamic forces did. Any turpopump failures you're fond of would have a similar effect, if anything liquid engines have less instantaneously stored explosive energy inside their engine pump/chamber unit. The entirety of the solid booster is the propulsion unit. Liquids provide more benign abort requirements.



Titan 34D- If you are referring to the 1985 launch, it was a propellant leak that shut down the liquids after launch.

He's talking about 1986 Titan 34D KH-9 launch: http://s76.photobucket.com/albums/j17/TomcatFanatic123/Titan%2034D%20explosion%20pictures/

Solid rocket booster failure at T+8 seconds.



Are the results of blowing a liquid some how“not bad”?

See above. Hypergols in particular cannot detonate because they cannot mix well before spontaneously igniting on contact.



Feel free to include links to backup your points.

I did. I suggest the same for you.



I read your link and I counted 4 failures in total. 2 solid and 2 liquid.

You ignore my count in my previous post of 3 solid-related immediate vehicle losses? All other failures, including turbopump going have a finite amount of time to initiate an abort, including Titan A-20 and Delta II premature MECO in 1986. There is no warning time for when a solid lets go and you can argue as long as you want, that won't change the facts.



Sounds like a permanent fix to me with no chance of reoccurrence. Those are the best kind of fixes.

Yeah, just make sure you tell that to family members of the ones lost after such "freak" failures occured. It'll make them feel much better.

The hindsight-talk of you people is incredible, it's as if the same statements about SRB safety weren't made before Challenger. The vehicle is always the safest right now, after the last catastrophe, until the next one comes along.



I suspect there are a dozen other ways that a turbo pump could fail. Each with a resulting boom! Now how many other failure points are there to liquids??
Does it matter if all of them are more benign and detectable ahead of time than SRB failure modes? Maybe to you only the number matters, not mode.

By your accounting it's apaprently better to have 1 catastrophic loss of vehicle with low to no chance of crew survival than 10 losses with very reasonable chances of survival. I know which chances I'd take. Two historic Soyuz crews were also very likely grateful they were sitting on top of a liquid vehicle when the excrement hit the fan.

The Jim
2009-Sep-21, 12:47 AM
I do my research as I find the time and need. I do include links to items I feel relevant. So I feel I “know something” and I’ll post as I chose. Feel free to include links to backup your points.

I don't need research to back up my points. I am in the spaceflight business. Since you aren't, you need to research. Additionally, your posts indicate that you need to do more research due to the incorrect points you make.

publiusr
2009-Sep-21, 08:00 PM
I don't need research to back up my points. I am in the spaceflight business. Since you aren't, you need to research. Additionally, your posts indicate that you need to do more research due to the incorrect points you make.

So here's some research for you Jim,
http://www.spacenews.com/commentaries/science-fact-science-fiction.html

ugordan
2009-Sep-21, 08:21 PM
So here's some research for you Jim,
http://www.spacenews.com/commentaries/science-fact-science-fiction.html
Wow, that's some really objective "research" there, given who wrote that piece:

Charlie Precourt, a retired U.S. Air Force colonel and former astronaut, is vice president and general manager of ATK Space Launch Systems.


Come on, you can do better than that. And you still keep talking about ULA "sales pitches"?

publiusr
2009-Sep-21, 08:31 PM
Oh thats right--a ULA presentation you will accept without question--like they aren't trying to sell a product too?

I noticed you left out some of his qualifications. Lets look at his whole pedigree shall we?

"Charlie Precourt, a retired U.S. Air Force colonel and former astronaut, is vice president and general manager of ATK Space Launch Systems. Precourt, a veteran shuttle commander, spent 15 years with NASA, during which he served as deputy program manager for the international space station, chief of the Astronaut Corps and director of operations for NASA at the Gagarin Cosmonaut Training Center in Star City, Russia."

Now call him a lier.

BigDon
2009-Sep-21, 08:39 PM
Wow, that's some really objective "research" there, given who wrote that piece:


Come on, you can do better than that.

How does that possibly preclude his opinion from being informed and valid?

ugordan
2009-Sep-21, 08:43 PM
Oh thats right--a ULA presentation you will accept without question--like they aren't trying to sell a product too?

Why shouldn't I as you have no problem dismissing much more credible data and claims than presented in this piece. You dismiss valid data and I'm providing a level playing field by dismissing this PR talk. He conveniently didn't address for example where the mass required for T.O. mitigation will come from. I guess from the nonexistent Ares mass margin. Better alert Lockheed to shave some more mass off of Orion then.

I don't give a damn about the guy's qualifications as he's tainted and frankly, from what I've heard so far of senior management involved in CxP, I wouldn't believe him if he said the sky is blue.

ugordan
2009-Sep-21, 08:45 PM
How does that possibly preclude his opinion from being informed and valid?
How does what ever EELV people or Jim here say precludes them from being right? Does that stop publiusr from making unsubstantiated attacks?

This piece is a PAO "all is well" message. There were many others related to Ares I before. What's next - believing Griffin that Ares I is the safest, simplest and soonest design in the world?

The Jim
2009-Sep-21, 09:01 PM
Oh thats right--a ULA presentation you will accept without question--like they aren't trying to sell a product too?

I noticed you left out some of his qualifications. Lets look at his whole pedigree shall we?

"Charlie Precourt, a retired U.S. Air Force colonel and former astronaut, is vice president and general manager of ATK Space Launch Systems. Precourt, a veteran shuttle commander, spent 15 years with NASA, during which he served as deputy program manager for the international space station, chief of the Astronaut Corps and director of operations for NASA at the Gagarin Cosmonaut Training Center in Star City, Russia."

Now call him a lier.

He is a marketeer, therefore his word is suspect. He had never worked on any launch vehicle, hence is word carries no weight.