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NASA contends that replacement of tiles in orbit is not possible, citing the 20,000 different tiles that are used on the shuttle as one reason. However, replacement tiles may be made in orbit.
The proposal: A few oversized green tiles are maintained on the space shuttle. If a missing or damaged
tile is found, a data bank provides a template, which can be matched by hand carving one of the soft green tiles. The green tile can then be fired in one of the materials science kilns onboard the space station.
[added] If not required for scientific reasons, the shuttle should be placed in an orbit within reach of the ISS.
Tile inspection and repair on orbit
http://books.nap.ed...tml/47.html#pagetop
We'll probably be hearing more about this [lurch, Oct 17 2004]
Shuttle Thermal Protection System
http://www.centenni...logy/TPS/Tech41.htm
Background. [Monkfish, Oct 17 2004]
STS-1
http://www-pao.ksc..../mission-sts-1.html
Ironically talks about tiles under 'mission highlights' [madradish, Oct 17 2004]
THERMAL PROTECTION SYSTEM
http://science.ksc....s_sys.html#sts-hrsi
More technical details on the tiles [pluterday, Oct 17 2004]
Dictionary.com
http://dictionary.r...m/search?q=kneejerk
No further comment required. [DrBob, Oct 17 2004]
Feynman's Appendix F
http://science.ksc....sion/Appendix-F.txt
Feb 03 2003. "The fact that this danger did not lead to a catastrophe before is no guarantee that it will not the next time, unless it is completely understood. When playing Russian roulette the fact that the first shot got off safely is little comfort for the next." [krelnik, Oct 17 2004]
Sally Ride comments yesterday
http://story.news.y...nm/space_shuttle_dc
Apr 09 2003 - "I'm think I'm hearing an echo here" [krelnik, Oct 17 2004]
[link]
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I'm guessing there would be some interesting issues with installing them, I believe the tiles are "glued" to the ship. You might need a different glue that could be applied in a vacuum. |
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Hey pluter, I wanted to email you yesterday after you deleted your camera idea. Don't back off so quickly! It turns out the robot arm is not carried on all flights, and in fact was NOT on board the Columbia yesterday. So your idea still has merit, despite the naysayers who were annotating you. Give it another try. (Please delete this annotation when you see fit). |
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[Krelnik] Thank you for saying that the camera platform idea had merit. Actually, I deleted it because I later found that this identical idea had already been tested on a shuttle flight...
I have been astonished to hear NASA officials say that they did not inspect for damage to the tiles, because if there had been damage, nothing could have been done about it. This is just rubbish. And, I expect that there were people who disagreed, just like before, but were overridden by management.
[lurch] It appears from your link that at least some work was done – like developing a foam in place thermal coating for non-critical areas, as well as a free floating camera. The fact is that there were options, including leaving the shuttle at the station for the time being. You have to wonder if the crew was even brought into the discussion. |
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I think within days we'll see a new category: "other: spacecraft: Shuttle safety". It's on a lot of minds right now. |
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//leaving the shuttle at the station for the time being//
That may or may not have been feasible on this mission. If the shuttle's orbit is significantly different than that of ISS, it wouldn't have had nearly enough fuel to do a rendezvous. |
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[krelnik] - or anyone - // If the shuttle's orbit is significantly different than that of ISS, it wouldn't have had nearly enough fuel to do a rendezvous // |
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Seems like the delta-v required for the deorbit should be sufficient to change the orbital inclination to match up with the ISS. I have an awful headache right now and would rather kill than do math, so somebody shout me down if I've got it wrong. I realize that using the fuel to get to the station would leave the shuttle - and crew - stranded in orbit... I, for one, heartily wish we were right now trying to figure out how to get those seven people off the ISS. |
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I understand docking would have been impossible. I don't understand why the shuttle & ISS were not designed with integral docking capability. |
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<later edit>Delta-v for deorbit is a *lot* less than I thought. It almost certainly would not be sufficient to alter the orbit enough to rendevouz with ISS.</later edit> |
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Last I heard, replacing tiles took upwards of 40 man hours
*on the ground*. Doing it in space would be next to
impossible, the materials science kilns would certainly not
be on every mission in any case. I don't want to think of
the effect that the space environment would have on
trying to use adhesives. [pluterday] I can see that you're
mad at what happened, but I think NASA are being honest
in their appraisals. I have to give this a fishbone because I
don't think that it is even vaguely possible much as I'd like
it to be. |
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[BinaryCookies] I've never heard of tile repair kits being
carried on the shuttle, it'd be good if you could provide
some evidence. As for NASA becoming complacent, some
tiles fell off in space on Columbia's first mission and they
considered it safe enough to bring down. |
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It would have been very difficult or impossible for
Columbia to reach the ISS. Columbia was older and
heavier than the other orbiters and thus was seldom used
for ISS missions. With the spacehab on board it probably
wouldn't have had enough fuel. |
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[lurch] the shuttle was designed back in the 1970s, the
ISS designers had to work with the system as it was. They
did the best they could under the circumstances. |
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I agree with [waugs] that pointing fingers doesn't help.
NASA does everything in their power to ensure the safety
of astronauts but they are not omniscient. The people
with NASA are probably feeling this the worst (other than
families). I have great sympathy for them and applaud
their dedication in the face of adversity. |
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Telling them that they should have tried harder won't
bring these seven back. |
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I think there is a reasonable argument for simplifling the shape of the space shuttle so you need less differently shaped tiles. Prehaps they should return to more of a single continious curved heat-shield concept that they used for the first space flights and missions to the moon. You might need to land in the sea, if you abandon the idea of a flying landing, but it might offer some advantages in terms of durability. |
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[lurch] Yeah I'm no good on orbital math, but going forward if they wanted to use ISS as a possible backup plan, they could voluntarily limit the Shuttle to orbits that are within achievable range of ISS. An open question is how debilitating a limit that would be, I know it would limit their launch windows. |
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As for the docking equipment not being on board, that is not an idea killer. In a rescue situation involving a different failure mode, parts of the shuttle including the RCS might be disabled. So docking might be dangerous anyway. Just get across to the ISS via EVA. |
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That reminds me of another question. When they have the "lab" in the cargo bay, do they still have a way to go EVA? Their normal airlock opens into the cargo bay, and becomes their door into the lab on these types of missions. Is there another airlock in the back of the lab? (I guess you could depressurize the main deck and go out the entry door in an emergency situation, that's on the side of the Shuttle). |
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In my mind, there is a design defect here from a systems analysis level that needs addressing. The safety of the mission depends on a part which is difficult, and perhaps impossible to replace in flight, and subject to statistical failure. |
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I propose that the tiles find a new method of attachment, although the problem may be the specialized tile material itself, and not a function of the glue. If I remember right from the solar car project, the Hysol (3M commercial airplane glue) we used was much stronger than the material that we bonded it with, (carbon fiber panels). |
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If the tiles interlocked somehow in addition to the glue, perhaps they'd be more inclined to stay in place. |
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I would think there would be a way to devise an adhesive compound that would supply its own environment for drying, given a way to 'bag' it. |
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//If the tiles interlocked somehow in addition to the glue, perhaps they'd be more inclined to stay in place.// |
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True, but then the only failure mode would be 'catastrophic' where a whole bank of tiles come off. |
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I just received an email with these (abridged) comments by a person that has been in the space program since Mercury. These comments have not been published, as far as I know.
"They didn't take care of the hardware…
"The leading edge of the wing is critical. If you get a gap between the RCC (leading edge of the wing) and the tiles you have a disaster. There are two segments of the RCC. If Plasma gets in there it goes everywhere. It punches
random holes.
"The plasma takes out the instrumentation first and then heats up the tire and blows up the tire which is right below the crew module. It then takes out the crew module. As a matter of fact we were worried about the tire design in the first place. People underestimate how much power is contained in the tires.
"Most of the things that would blow up are in the back, the APO'S, OMPs Pods, if one of those had blown up the crew would have been aware and not just suddenly stopped talking with ground control. As it was they noted problems with the instrumentation, the tires and then just stopped talking altogether.. which would be consistent with the crew module having blown-up."
This makes me wonder if draining the air pressure from the tires could have bought enough time to get the shuttle low enough to eject. |
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I believe the quoted text is referring to the front landing gear tires which are directly below the crew compartment. This is different than the left rear landing gear tires, which is where the sensors went out---these are far behind the crew compartment. However it is in an interesting comment. |
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<krelnik> You are correct, I believe. This NASA veteran’s logic appears to be flawed. Perhaps he is senile. |
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[[In a now-deleted annotation, waugsqueke said...]]
//There has been impact damage to it on ascent in the past and it has never compromised missions before.//
The late, great Richard Feynman pointed out the inherent fallacy of this kind of thinking in his Appendix F to the Rogers Commission report on the Challenger disaster. (see link). His bottom line was that we should expect to lose a shuttle in one out of 100 flights, and it seems he was unfortunately prescient. |
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Please read the link, waugsqueke, I've provided a secondary copy. |
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[krelnik] I do not see that waugsqueke is trolling you. He
is simply coming to terms with this tragedy as are the rest
of us. I'm sure you are not helping him. If you can't say
anything nice, please piss off. |
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I've removed the comment about trolling, since [waugs] removed the most offensive part of his annotation (which I'll assume you did not see [madradish]). |
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I read that NASA doesn't train for "no win" situations, since such training would be analagous to telling a motorist what to do after his car goes off a 400' cliff. On the other hand, the failure that occurred on Apollo 13 was one which had previously been deemed a "no win" situation and yet the astronauts survived. |
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I think one of the big problems in this particular situation is that people may have recognized that there was a certain likelihood of failure, but any contingency plans would necessarily involve considerable risk. In the case of Apollo 13, many of the decisions were easy in the sense that the alternative to trying out the new untested procedures was certain death. In this case, the alternative to accepting an unknown risk was accepting a different unknown risk. |
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To my mind, the one thing which could have been tried if the damage were believed to be significant and circumstances permitted would have been to buy a launch-ready Soyuz from the Russians and retarget it to rendezvous with the shuttle, carrying a supply of life-support goods and diagnostic equipment (EVA tethers, cameras, etc.). This would get two crew members home and hopefully provide enough time to outfit a second Soyuz capsule with the goods needed to make a repair. |
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Of course, if a Soyuz can't be prepared and launched within a week of finding the original problem, that approach won't work. |
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Out of curiosity, how do the launch, recovery, and reprep costs of the shuttle compare with those of the Russian's Soyuz program? Even when everything goes right, I doubt that the shuttle really saves money. To the extent that high-stress components have to be built tougher (and heavier) to survive multiple takeoff/landing cycles than they would have to be to just survive one, and to the extent that frequent major overhauls are required on the Shuttle, it would seem that building a craft to survive one takeoff, and protect the crew well enough for one landing, would be a more practical design. |
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[supercat] What is the limitation here? Is it oxygen, food, water, what? Why can't the crew go for a few days without food or water? I can understand if it was oxygen... |
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The limitation was the soon-to-be-ex head of NASA's ego I think. Just because the shuttle couldn't have reached the ISS doesn't mean they had to de-orbit that day. It also doesn't mean they couldn't have sent the Soyuz capsule down to get them or something. I know that this too could have been impossible for any number of reasons, but it seems to me that the people who got what was essentially half a spaceship, that wasn't anywhere near Earth orbit (Apollo 13) home gave up. Of all the things I've seen, this I find to be one of the most shocking. I mean really, what kind of excuse is : "We didn't look because there was nothing we could do anyway." Inevitability I can accept, but a half-assed job I cannot. There may have been nothing that could be done for that crew, though I doubt it. Even so, I find it hard to believe so little was done for them as there was. |
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MadCat: I don't think they knew the Shuttle was doomed. They may have realized it had a 50% chance of destruction on re-entry, but even if they knew that, what would you have had them do? |
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The rescue of the Apollo 13 astronauts was a 1000:1 shot; since the astronauts had no other choice, however, they took it. Using unprecedented procedures and having a 0.1% chance of rescue and a 99.9% chance of ending up dead is still better, though, than following normal procedures and having a 0% chance of rescue and a 100% certainty of ending up dead. |
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In this case, trying unprecedented procedures might, in retrospect, have saved the astronauts but I doubt there was any way that could be known at the time. I would think it likely that NASA figured such procedures would be more likely to make the mission fail when it otherwise would have succeeded, than to make it succeed where it otherwise would have failed. |
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It appears that Sally Ride may agree with my February 3 annotation, re: Feynman's analysis of the fallacies of logic about safety margins that led to both shuttle disasters. Yesterday she said: "I'm think I'm hearing an echo here," referring to how foam hits on the shuttle had been seen before, but had not been considered a problem. See link. (To read what she is hearing an echo of, see the link above it to Appendix F of the Rogers Commission report). |
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I think what they need is to have an extra shuttle parked at the station. If the launced one is damaged, they can either go back down on the spare or cannibalize the extra ship for spare parts. ( replacement can be sent on the next mission) |
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Science, schmience. What I wanna know is: can you play Scrabble In Space with these tiles? |
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