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sts60
2003-Feb-26, 07:01 PM
A guy on a mailing list I frequent wants to avoid Columbia-type problems by the following...

1. Slow down via OMS firing.
2. Aerobrake until heated up to a predetermined amount.
3. Use control surfaces to maneuver back up to less dense air (speed-for-altitude).
4. Cool off.
5. Repeat until Orbiter has lost most horizontal velocity component.

Basically, he wants to take reentry in little bites. He acknowledges that major modifications would be necessary.

I see the following problems with this:
1. Using control surfaces to maneuver back up would destroy them by aerodynamic/thermodynamic loads.
2. Can't reject heat gained on aerobraking dip.
3. Will burn up on one of the aerobraking dips as angle too steep while fwd velocity component is too high still (overall speed too great) => incineration/disintegration.
4. Overall aerodynamic loads too great at some point(s) in this scheme anyway.

Comments? Anything I forgot? I'm a sparky/code weenie background, not a wrenchie or thermo-guy....

CJSF
2003-Feb-26, 07:05 PM
I don't see how #3 would work. How can you regain altitude using the control surfaces? You'd need thrust for that.

CJSF

frenat
2003-Feb-26, 07:09 PM
You would need extra thrust and at that heightin the atmosphere, there is simply not enough air for the conrol surfaces to to anything. That is why the maneuvering was still being controlled by the attitude control jets.

JackC
2003-Feb-26, 07:14 PM
Gosh - the problems involved with all these points are just incredible.

Point 1: They DO use engine braking now - that's how they begin descent. What this person is talking about is more like using a LOT more fuel for heavy braking - where's that fuel come from? Many other problems/issues.

Point 2: Aerobraking is done now - that is what caused the heat. You can't go to a pre-deteremined amount and just stop though!

Point 3: Addressed a bit above, but "control surfaces" aren't very effective until you have already lost a goodly amount of speed and are into thicker atmosphere.

Point 4: Cool off how? Presumably by "going higher" or stopping the descent. Perhaps we should remind this person the STS is a GLIDER at this point. Gliders go one way - down. Some go down slower than others. This particular one is not noted for it's height retention capabilities when "on approach"!

Point 5: moot because points 1-4 don't work.

Perhaps they are thinking of a shampoo bottle?

Physics is a very difficult thing to get around - no matter what the wishful thinking.

Jack

sts60
2003-Feb-26, 07:36 PM
Good points all. You do trade airspeed for altitude in ordinary aircraft, but as you are saying, this isn't an aerobatic glider at 2,000 feet and 80 mph. Sticking the elevons down up there wn't do much except, presumably, lose you the elevons in short order...

BTW, another person on the list has posted the following interesting links:

The URLs below provide images of the Columbia that were taken by the U.S. Air Force Maui Optical and Supercomputing Site on January 28.

Visible light:
http://spaceflightnow.com/shuttle/sts107/030225amos/visible.html

Infrared:
http://spaceflightnow.com/shuttle/sts107/030225amos/ir.html

-John Hall
I wonder if they have any that clearly show the port wing closer in, top or bottom?

SAMU
2003-Feb-27, 07:59 AM
Just to address the issue of using orbital energy to maintain altitude until speed has decreased to allow reduced heating of the orbiter.

Some, in reply to this post, have objected to that idea on the basis that aerodynamic "maneuvers" cannot be accomplished at that altitude for various reasons, heating , thinness of the air, tearing off of control surfaces etc. To them I would point out that the shuttle accomplishes banking "maneuvers" to disipate orbital energy anyway. To "maneuver" to retain altitude in thinner air for longer to reduce heat loading is feasable. It's called "skipping" or for conventional aircraft a "minimum sink" attitude (staying airborne for longer time, sacrificing speed and distance). Which is basically a nose high attitude compared to a slightly lower nose attitude required for "best glide" (staying airborne for longer distance sacrificing time aloft). Clearly, since the orbiter has so much orbital energy that it must perform several banking maneuvers to disipate it, it could also use the energy to maintain altitude in thinner air for longer to reduce reentry stresses. Because it is remaining in thinner air for longer and sheding orbital energy more slowly it might have to perform wider banking maneuvers or reenter earlier (farther uprange).

Some will still object with "just because it can bank right or left dosn't meen that it can climb or maintain altitude. To them, all I can say is you just don't know how to fly. Even if you are a pilot you are just forgetting a detail.

This has happened to me before. I was taking off with my instructor on a hot day. Presumably he was fairly experienced (800 hrs.). He said "Remember, you have to take off faster on a hot day." Being in the middle of a takeoff run I quickly replied (actually I shouted over the sound of the engine) "Remind me to ask you about that later." And I took off at the usual take off airspeed for a Piper Tomahawk of 60 mph. After about five or ten seconds of thought he said" You're right, you're right, I made a mistake telling you that."

The issue was that on a hot day the air is thinner. So you must pass through more space to get enough air to get to your take off airspeed. Not that you need more airspeed but that you need more runway to get to your required airspeed.

Thumper
2003-Feb-27, 12:28 PM
On 2003-02-26 14:36, sts60 wrote:

The URLs below provide images of the Columbia that were taken by the U.S. Air Force Maui Optical and Supercomputing Site on January 28.


Those are fascinating photos. Did anyone notice the different look of the two payload bay doors. The starboard door appears uniform, one continuous door. The port door appears split in two with the front half not open as wide as the rear half. Is that what I'm seeing? Are there separate segments to the doors that can move independantly?

(fixed BB code)

<font size=-1>[ This Message was edited by: Thumper on 2003-02-27 07:30 ]</font>

kucharek
2003-Feb-27, 12:49 PM
All this stuff is heavily discusses on sci.space.shuttle and I suggest you go there for more detailed information.


> Hrm, definately looks as if something is amiss on the left bay door, probably
> the aft radiator is under-deployed? Is that an unusual configuration?

No, that's normal. The two rear radiators on each door are fixed in position, they don't deploy. What I see here are the forward radiators on the left door deployed while the radiators on the right door are stowed.
Could have been part of the cooling problem workaround for the SpaceHab module.



At http://www.io.com/~o_m/columbia_loss_faq_x.html is a pretty comprehensive FAQ available and I read that your subject is currently worked into it.

Harald

<font size=-1>[ This Message was edited by: kucharek on 2003-02-27 07:53 ]</font>

Roy Batty
2003-Feb-27, 12:55 PM
Darn, beaten to it /phpBB/images/smiles/icon_smile.gif
This has some pretty good info too:
http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts_coord.html#payload_bay_doors

_________________
N6MAA10816

<font size=-1>[ This Message was edited by: Roy Batty on 2003-02-27 07:56 ]</font>

Thumper
2003-Feb-27, 06:03 PM
Thanks for those links. I remember reading through the KSC Shuttle reference site a few years back but hadn't gotten around to trying to find it again. Pretty thorough stuff for a layman.

daver
2003-Feb-27, 06:05 PM
On 2003-02-27 02:59, SAMU wrote:
Just to address the issue of using orbital energy to maintain altitude until speed has decreased to allow reduced heating of the orbiter.



Sanger's skip bomber was supposed to "bounce" off the atmosphere multiple times. If Apollo's reentry angle was too shallow it was supposed to skip off. The shuttle might need to be redesigned to skip, but i'm not sure that it is aerodynamically impossible.



..."Remember, you have to take off faster on a hot day."


I'm not a pilot, i don't know what i'm talking about, but i'm curious.

Density altitude? Lift sure seems like it should be proportional to the density of the air as well as to your speed. Was he saying that your pitot tube automatically compensates for air density--that your indicated air speed is a function of air density and actual air speed?

I remember stories of underpowered, overloaded WWII bombers having to take off for their runs at night or morning, also of GA craft having problems taking off from Denver in the afternoon because of problems getting enough lift in the warmer air.

patrioticamerican
2003-Feb-27, 06:21 PM
Good and interesting points. Barring the possibility of turning the Shuttle into a powered airplane rather than a glider, here's what NASA should have done:

First, I was surprised that the astronauts didn't have the capability to inspect the exterior of Columbia, either with the arm or an EVA. Because of the fragile nature of the system, they should ALWAYS have that capability. And I still find it hard to believe that they didn't try to inspect Columbia with ground based telescopes, especially after discovering the wing impacts. Dittemore said from past experience they wouldn't have gleaned any useful info, however, new/modified scopes using adaptive optics possibly could have shown problems (if they existed, which isn't known with any certainty). Was certainly worth a try.

If a risk of flight issue had been determined early in the flight, the crew could have been put on minimum life support, ala Apollo 13, to extend their time in orbit. Atlantis, which was being readied for an early March launch, possibly could have been used as a rescue vehicle - IF it could have been readied and safely launched in time (a big if) - with just a "skeleton" crew.

Atlantis could have transferred 7 spacesuits (if they didn't have them, I don't know) to Columbia, and the astronauts could have EVA'd to Atlantis, and returned (hopefully safely) to Earth. Then NASA could have attempted to either repair Columbia, and/or bring it home un-manned, which as far as I know is possible via onboard computers and remote control, landing on auto-pilot at Edwards AFB (much more room for error).

Imagine how thrilling such a rescue mission would have been, and what great PR it would have given NASA. Instead, we have this tragic, horific accident.

20-20 hindsight - lots of ifs - but NASA has to be agonizing over what possibly could have been done. If anyone has any ideas on why this rescue scenario wouldn't work, I'd love to hear them.

JackC
2003-Feb-27, 06:48 PM
Some will still object with "just because it can bank right or left dosn't meen that it can climb or maintain altitude. To them, all I can say is you just don't know how to fly. Even if you are a pilot you are just forgetting a detail.

SAMU: I fly too - have done so for quite some time. I suggest you try something - though at present, it will have to remain a thought experiment.

Take your little Tomahawk into Halealaka creater. Oops - I don't think you can - I don't believe the service ceiling in a Tomahawk goes that high. (Well, actually, it does - but only just - which is why doing this is now illegal... and must remain a thought-experiment!)

But if you could, you would find something interesting (for the record, I HAVE done this) - the plane does not fly straight-and-level. Reason is, there isn't enough air to hold it up adequately. You have to apply ample power to haul the bird up in the thin air and make it "fly straight" - with a nose-up attitude of about 15 degrees or so.

And this is only at 10k feet. Admittedly with a VERY underpowerd aircraft (Cherokee 140 in my case...)

The point is - if I WANTED to "maintain altitude" while at that altitude - I had ONLY one option - apply power and lots of it. The shuttle does not have that option. While flying at "best glide" in normal air, you DO have a little bit of an option to climb or at least maintain - but at the stage where 107 started to die, "flying" was not really the operative word. Controlled falling was pretty much more descriptive.

As you note in any event, you trade distance and speed for altitude if you have the ability to pull up and hold thinner air for a bit. My opinion is that this option is not open to a bird falling through thin atmosphere at 18c... er... 10kmph, but if it were, it would SIZEABLY modify the approach path - which is a one-shot deal. Holding altitude for any significant length of time (enough to cool things) would definately require power in any event. you can't "stretch a glide".

Flying in the thick air is not quite like flying in the upper reaches, I am afraid.

BTW: I also used to fly a wonderful Cherokee Arrow - that was eventually trashed killing three of the four souls aboard because the pilot at that time didn't believe in physics - and tried to stretch his run by trading speed for altitude and finding the tops of trees rather unforgiving.

Physics really is the ultimate arbiter here.

Jack

Firefox
2003-Feb-27, 07:11 PM
First, I was surprised that the astronauts didn't have the capability to inspect the exterior of Columbia, either with the arm or an EVA.

There wasn't much of a need to, since the RMS would have been an issue with the large SpaceHab module in the payload bay. There were also no MMUs on the flight, and if I recall, they didn't even have the smaller emergency maneuvering units.


Because of the fragile nature of the system, they should ALWAYS have that capability.

I've heard of arguments that inspection should be done, but I can't remember hearing of a time when it was done with the belly of the orbiter. The RMS can't view all areas of the ventral surface, and having astronauts go down there to inspect is a dangerous prospect, both with tether vs. no tether, or the chance that poking around would damage more tiles.


And I still find it hard to believe that they didn't try to inspect Columbia with ground based telescopes, especially after discovering the wing impacts. Dittemore said from past experience they wouldn't have gleaned any useful info, however, new/modified scopes using adaptive optics possibly could have shown problems (if they existed, which isn't known with any certainty). Was certainly worth a try.

I'm not sure if this is much of an option, and it would depend on the orbit. I'm sure that will be taken into consideration on future missions, though.


If a risk of flight issue had been determined early in the flight, the crew could have been put on minimum life support, ala Apollo 13, to extend their time in orbit. Atlantis, which was being readied for an early March launch, possibly could have been used as a rescue vehicle - IF it could have been readied and safely launched in time (a big if) - with just a "skeleton" crew.

That's the most realistic scenario I've heard of, IMO. Certainly more realistic than trying to fly the shuttle to the ISS, since they were in the wrong orbit.


Then NASA could have attempted to either repair Columbia, and/or bring it home un-manned, which as far as I know is possible via onboard computers and remote control, landing on auto-pilot at Edwards AFB (much more room for error).

They would have likely risked a re-entry as you suggested, since repairs are pretty much out of the question. There's no capability to replace tiles in orbit.

That's been one of my pet peeves lately, too. The argument that they should have sent up a "patch kit", and should include it on every shuttle flight. People who argue in favor of that don't understand what's needed to put the tiles in place, as well as their delicate nature.


-Adam

joema
2003-Feb-27, 08:04 PM
On 2003-02-27 13:21, patrioticamerican wrote:
First, I was surprised that the astronauts didn't have the capability to inspect the exterior of Columbia, either with the arm or an EVA...And I still find it hard to believe that they didn't try to inspect Columbia with ground based telescopes, especially after discovering the wing impacts...new/modified scopes using adaptive optics possibly could have shown problems (if they existed, which isn't known with any certainty)...
If a risk of flight issue had been determined early in the flight, the crew could have been put on minimum life support, ala Apollo 13, to extend their time in orbit. Atlantis, which was being readied for an early March launch, possibly could have been used as a rescue vehicle...repair Columbia, and/or bring it home un-manned, which as far as I know is possible via onboard computers and remote control

Columbia didn't have the robot arm -- it was removed to give room for the SpaceHab module.

Some in NASA did want to inspect it with the Maui AEOS or Starfire adaptive optics telescopes. DoD started marshalling the resources, but then it was shut down because of not being requested through appropriate channels. Here are the actual emails (it's toward the bottom), 2.4MB .pdf file:
http://www.msnbc.com/modules/space_pdfs/COL_email_030226.pdf?0cb=-113139197

If the damage had been identified very early in the mission, there was a small possibility of an Atlantis rescue. Atlantis was already being prepped for a nominal March 1 launch (six weeks after Columbia liftoff). Columbia had about 16 days nominal consumables, probably 20 days absolute. They could have probably stretched this 50% to 30 days (Apollo 13 stretched nearly 100%). If Atlantis processing could have been expedited from six weeks to about four weeks, it might have worked. However there would be risk Atlantis could encounter the same problem that damaged Columbia, plus all the EVA risks and expedited launch risks.

The shuttle can almost make an unmanned return but not quite. The autopilot was significantly enhanced as part of the EDO (Extended Duration Orbiter) kit to allow mostly unpiloted operation, in case the pilot was partially incapacitated by the long mission. However a few items like dropping the landing gear are fully manual and require a human on board. In the future these could easily be automated, but current orbiters require manual intervention.

-- Joe

joema
2003-Feb-27, 08:15 PM
On 2003-02-26 14:01, sts60 wrote:
A guy on a mailing list I frequent wants to avoid Columbia-type problems by the following...
2. Aerobrake until heated up to a predetermined amount.
3. Use control surfaces to maneuver back up to less dense air (speed-for-altitude).
4. Cool off.
5. Repeat until Orbiter has lost most horizontal velocity component.

This is called a skip reentry. It was planned for the X-20 Dyna-Soar. It is theoretically possible but wouldn't have helped Columbia, nor was it possible for Columbia.

A skip reentry places much higher peak heat loads and G loads on the airframe. The shuttle's airframe and thermal protection (TPS) is designed for a specific reentry profile, not a skip profile. Basically it would break up or burn up trying a skip reentry.

If a lower-heat reentry was possible, they'd have designed the shuttle's TPS around that and saved a lot of weight.

-- Joe

<font size=-1>[ This Message was edited by: joema on 2003-02-27 15:16 ]</font>

Thumper
2003-Feb-27, 08:24 PM
Many of the topics brought up by patrioticamerican have been discussed before in several threads on this board. I'd search and link but I just don't have time right now. The links above are very informative. Here's another:Space.com. (http://www.space.com/columbiatragedy/) It's FAQ page is pretty comprehensive.

The topic of some sort of tile patching material has been brought up. To date according they have been unable to create a caulk or patching material that can successfully be applied in the vacuum of space. (I learned this listening to a former astronaut being interviewed on TV right after the tragedy. His name currently escapes me.) This is in addition to the multitude of other problems with trying to get an astronaut safely down there, in a position able to perform the work, and back.

Joe is correct, the Shuttle has a very comprehensive autopilot but currently needs human pilots for several key tasks including lowering the landing gear.

(fixed BBcode)




<font size=-1>[ This Message was edited by: Thumper on 2003-02-27 15:26 ]</font>

Thumper
2003-Feb-27, 09:05 PM
On 2003-02-27 15:15, joema wrote:

If a lower-heat reentry was possible, they'd have designed the shuttle's TPS around that and saved a lot of weight.

There have been more "Why didn't they do this" or "could they have tried this" scenarios than I can count. IMO you can bet that nearly every one if not all of these ideas have been bantied about, discussed, tested, simulated and what not for YEARS prior the final designs, ascent profiles, re-entry profiles, not to mention the construction and first launch.

The risks, benefits, tradeoffs etc. would have been looked at and the best possible system was developed given the technology available, budget constraints et al.

The shuttle was designed to do exactly what it usually does, as safely and efficiently as possible. There are certainly risks. They have been mitigated and compared to the risks and benefits of many other types of systems.

patrioticamerican
2003-Feb-28, 02:29 AM
Thanks for all the good info. Really surprised to learn that the landing gear doors have to deployed manually. And thanks for the pdf of NASA e-mails - fascinating reading, especially the one where Daugherty says the damage/thermal analysis was done for a strike on the gear door or wing only and not the door/wing interface, and that their conclusions about burn through could be incorrect for the interface/seals. Hard to believe that they wouldn't do that analysis, so I wonder if that's in error?

We can speculate forever on what could have been done. It's even quite possible that the foam didn't cause the damage that resulted in the catastrophe. Still, one thing that really irks me is that NASA went to an inferior ET insulation foam because of EPA requirements. Why would they do ANYTHING to compromise the safety of this incredibly complex and expensive machine, not to mention the lives of it's crew?

A couple years ago my rocket propulsion prof said that the pollution from one Shuttle launch is roughly equivalent to all the pollution caused by automobiles in the LA basin in one month. If that's true (have no reason to doubt him) why should they be so concerned about the relatively small amounts of CFCs (or whatever) in the ET foam? Seems almost mind boggling in its stupidity.

patrioticamerican
2003-Feb-28, 02:52 AM
I agree Thumper, when you consider the complexities and extreme environments of a shuttle mission, it's pretty amazing that they had something like 86 consecutive succesful flights post-Challenger, and 111 re-entries without failure. Yet, no matter how smart we are we're only human, and prone to mistakes. Using an inferior foam on the ET - especially when it had caused problems in the past - is definitely one of them.