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tdn
2004-Jan-27, 06:01 PM
I'm only up to episode 8, so please don't post any spoilers!

Two things I've noticed:

1) In episode 1, Sheppard goes up in a Mercury rocket that has, for some reason, almost no visible exhaust. Perhaps that was a realistic depiction, but to me it seemed very odd.

2) It was suggested (if not stated outright) that Armstrong made his "one small step" comment off the cuff, rather than planning it in advance. He was also misquoted.

Any others?

ToSeek
2004-Jan-27, 08:12 PM
I'm only up to episode 8, so please don't post any spoilers!

Two things I've noticed:

1) In episode 1, Sheppard goes up in a Mercury rocket that has, for some reason, almost no visible exhaust. Perhaps that was a realistic depiction, but to me it seemed very odd.



Like this? (http://www.floridatoday.com/news/space/images/2001a/may/freedom7.jpg)

tdn
2004-Jan-27, 09:04 PM
I'm only up to episode 8, so please don't post any spoilers!

Two things I've noticed:

1) In episode 1, Sheppard goes up in a Mercury rocket that has, for some reason, almost no visible exhaust. Perhaps that was a realistic depiction, but to me it seemed very odd.



Like this? (http://www.floridatoday.com/news/space/images/2001a/may/freedom7.jpg)

Er, yeah. Just like that.

My bad.

Moose
2004-Jan-28, 08:06 PM
Hi Todd, good to see you again.


I'm only up to episode 8, so please don't post any spoilers!

Two things I've noticed:

1) In episode 1, Sheppard goes up in a Mercury rocket that has, for some reason, almost no visible exhaust. Perhaps that was a realistic depiction, but to me it seemed very odd.


*grin* As ToSeek pointed out, it's true that the propellant used on the Mercury missions produced a far less... spectacular flame than, say, that used by the Saturn V.

Interestingly enough, you're on the right track with your line of thought. The LM's propellant is also invisible, but was depicted as producing a blue flame for, I presume, dramatic effect in the previous episode.

That said, as you'll see in episode 12, the LM's ascent stage correctly produces no visible flame.

Zamboni
2004-Jan-28, 10:54 PM
Hmm... So are the fuels used by shuttle launches especially designed to give off smoke an flame? Or is it just so happens that more powerful propellants excrete more junk?

daver
2004-Jan-28, 11:02 PM
Hmm... So are the fuels used by shuttle launches especially designed to give off smoke an flame? Or is it just so happens that more powerful propellants excrete more junk?

The SSME's exhaust is almost invisible; the solid rocket boosters are what make all the smoke. So I suppose it depends on what you mean by "more powerful".

ToSeek
2004-Jan-29, 01:39 AM
Hmm... So are the fuels used by shuttle launches especially designed to give off smoke an flame? Or is it just so happens that more powerful propellants excrete more junk?

It's just a question of the propellant and oxidizer used. Some result in a transparent exhaust (hydrogen and oxygen, as with the space shuttle main engines), others don't.

AstroSmurf
2004-Jan-29, 09:06 AM
I would also guess that a lot of the smoke at a shuttle launch is water vapor - ISTR some sort of water dump tanks were used to dampen the sound of the engines, and probably to cool down the launch platform as well.

Interestingly, I watched a Discovery show about the Antonov 225 the other day, and they mentioned that the Russian near-copy of the shuttle, the Buran, has no engine in the actual shuttle and relies on external boosters using liquid propellant. According to the show, this resulted in a LOT more cargo carrying capacity.

This made me very curious why the shuttle is designed this way - the only reason I can think of to attach main engines would be to give it better maneuverability in orbit, but since the external boosters can be stopped and restarted, I'm left slightly puzzled...

Sparks
2004-Jan-29, 09:10 AM
This made me very curious why the shuttle is designed this way - the only reason I can think of to attach main engines would be to give it better maneuverability in orbit, but since the external boosters can be stopped and restarted, I'm left slightly puzzled...
The external boosters on the shuttle are solid rockets - they can't be stopped once started. Which was a major concern during design and testing - noone had used solid rockets in a manned spacecraft in the US to that point. (I'm not sure about the USSR, I thought that they had used them there as first-stage strap-on boosters).

AstroSmurf
2004-Jan-29, 11:56 AM
I found my answer - the Energia booster (which was what I was talking about being restartable) burns up in the atmosphere, so it simply costs more to use than having reusable SRB's. Pity.

http://www.hightechscience.org/buran_space_shuttle.htm

To get back on the subject, I haven't noticed any particular goofs in the show. It was on in Sweden during the early morning hours, so I didn't get to watch it. Going to get it on DVD, but it costs a small fortune. I'm wavering between the HBO show and getting the disks with the original footage.

daver
2004-Jan-29, 05:06 PM
This made me very curious why the shuttle is designed this way - the only reason I can think of to attach main engines would be to give it better maneuverability in orbit, but since the external boosters can be stopped and restarted, I'm left slightly puzzled...

The shuttle was originally designed to be entirely reusable--the thought was, "Why throw away your main engines after every flight--we can save oodles of money by bringing them back and reusing them." As has been seen, this didn't pan out.

The main engines can't be restarted once shut down. As Sparks said, the external boosters can't be shut down. This has always been a concern--the solids give a bumpy ride, and in the event of a failure (solid fails to start, solid burns through during the boost) there is no recovery mode--loss of orbiter and crew is pretty much guaranteed.

daver
2004-Jan-29, 05:21 PM
I found my answer - the Energia booster (which was what I was talking about being restartable) burns up in the atmosphere, so it simply costs more to use than having reusable SRB's. Pity.

The cost savings of reusing the SRBs are also subject to some debate.

Sparks
2004-Jan-29, 06:01 PM
The shuttle was originally designed to be entirely reusable--the thought was, "Why throw away your main engines after every flight--we can save oodles of money by bringing them back and reusing them." As has been seen, this didn't pan out.
Ah now lads, hold on there a minute. The original plans for the shuttle got so mangled that you can't really point to it and say that it shows too much about RLV design other than design-by-committee doesn't work for RLVs either. The original design for the shuttle would have been far more economical.

The shuttle, don't forget, is pretty much the largest collection of engineering "donnts" arranged in one package that we've ever produced...

calliarcale
2004-Jan-29, 08:59 PM
The shuttle was originally designed to be entirely reusable--the thought was, "Why throw away your main engines after every flight--we can save oodles of money by bringing them back and reusing them." As has been seen, this didn't pan out.

The Soviets originally had this intention with Buran as well, and intended to make the entire Energia stack (core stage and four liquid boosters) reusable. The idea was that they'd fly back to Earth. But their technology wasn't quite up to reusable cryogenic liquid engines yet, at least not ones of that size. The SSMEs are quite unique, as the only reusable cryogenic engines ever put into fullscale use.


The main engines can't be restarted once shut down. As Sparks said, the external boosters can't be shut down. This has always been a concern--the solids give a bumpy ride, and in the event of a failure (solid fails to start, solid burns through during the boost) there is no recovery mode--loss of orbiter and crew is pretty much guaranteed.

That's not strictly true. If both solids fail to start, there is not a very large risk of a catastrophic problem -- the main engines will be shut down and the launch aborted. There is a very small period of time between SRB start and hold-down release to allow for this. If only one lights, then there is a bigger problem, since this will result in a strong offcenter thrust. The lucky thing is that solids are very reliable. The odds of this happening are negligible. Now, the SRBs were implicated in the Challenger disaster, but it's not because they blew up as many people think. They actually kept burning several seconds after the vehicle was lost, until range safety sent the destruct command. The actual problem was a leaky seal allowing hot gasses to get where they should not be.

The minute and a half while the solids are burning is pretty much a time of no abort options, this is true. There isn't a good way to resolve that either, I'm afraid. After SRB separation, there are some options -- Return To Launch Site, TransAtlantic Landing, Abort Once Around, and Abort To Orbit. ATO is the only one which has ever been used, and luckily that abort occured late enough that although the desired orbit was not acheived, it was still sufficient to complete the mission.

tdn
2004-Feb-03, 10:20 PM
Hi Todd, good to see you again.

Hey, Moose! :D

Thanks to everyone for dispelling my misconception about Mercury exhaust.

One interesting thing about this series (which I've finished, but I want to watch again from the beginning) -- I thought it would be cool to find a few places where there was obvious fakery (since much was obviously faked). You know, the Rover kicking up dust clouds, objects falling at different rates (hammer/feather), etc. SOME clue that would show that they filmed this on Earth. I thought this would be excellent proof to HBers that some things just cannot be faked on Earth, that some original footage could not have been filmed anywhere but on the Moon. "Hey, we can't fake it now, we couldn't possibly have faked it way back in the early 70s."

But bugger all if I could find a single thing. If anything, this series has convinced me that we almost COULD pull off a hoax, at least with today's technology. That's some fine film making.

SpaceTrekkie
2004-Feb-03, 10:30 PM
I thought that serious was wonderful! wasn't it like 18hrs worth. Watched it in less than 3 days (okay so i dont have a life) a while ago. absolutly wonderful...i quote from it all the time to my friends! and you are absoulutly right, it could be used as evidence against the HBers. have fun watching it again it is even better the second time!

[edited to fix typos]

johnwitts
2004-Feb-03, 11:38 PM
The dust thrown out by the LM engine on descent is billowing, and not travelling in straight lines. Plus, because the Moonwalkers are made lighter by balloons, they seem to have trouble with their lateral motion. RCS thruster firings on the LM seem to be left behind by the LM, but that wouldn't be seen on a real mission anyway. Other than that, I can't think of any other 'whistle blows' but it's been a while since I watched it.

daver
2004-Feb-04, 01:34 AM
Ack. I should proofread better.


That's not strictly true. If both solids fail to start, there is not a very large risk of a catastrophic problem -- the main engines will be shut down and the launch aborted. There is a very small period of time between SRB start and hold-down release to allow for this.

Agreed.


If only one lights, then there is a bigger problem, since this will result in a strong offcenter thrust.

This is the situation I meant to describe. I've heard this called a pinwheel.


The lucky thing is that solids are very reliable. The odds of this happening are negligible. Now, the SRBs were implicated in the Challenger disaster, but it's not because they blew up as many people think. They actually kept burning several seconds after the vehicle was lost, until range safety sent the destruct command. The actual problem was a leaky seal allowing hot gasses to get where they should not be.

Yes. I should have been more explicit that I wasn't describing a Challenger-type situation. A failure of one of the solids while both are burning is potentially non-recoverable. However, as you note, they are extremely reliable.

Maksutov
2004-Feb-04, 03:25 AM
I would also guess that a lot of the smoke at a shuttle launch is water vapor - ISTR some sort of water dump tanks were used to dampen the sound of the engines, and probably to cool down the launch platform as well. [edit]



If you're looking at the classic view of the shuttle stack at launch, i.e., from the side with the tower behind the vehicle, there will first be a cloud of steam expelled to the left as the exhaust of the main engines hits the waterfall, then about 6 seconds later there will a cloud of aluminum oxide and acidic gasses, such as hydrogen chloride, to the right as the SRBs ignite. The smoke column above the pad is entirely due to the combustion by-products of the SRBs.