Mageth

A couple of more things about repairing tiles in space:

- There is a risk that the astronaut would cause as much or more damage than he/she would fix.

- From here:

The RTV silicon adhesive is applied to the orbiter surface in a layer approximately 0.008 inch thick. The very thin bond line reduces weight and minimizes the thermal expansion at temperatures of 500º F during entry and temperatures below minus 170º F on orbit. The tile/SIP bond is cured at room temperature under pressure applied by vacuum bags.

The properties of the adhesive (in its liquid state) used to adhere the tiles to the shuttle in the vacuum and cold of space is questionable, to say the least. Thus I'm not certain that it could be applied succesfully on orbit. And one certainly couldn't perform a room temperature curing under pressure.


One more note about sending up a "rescue" shuttle:

If it was obvious that there may be a serious systemic problem (e.g. insulation from the main tank breaking off and hitting the wing) that is a significant risk to damage to tiles during launch, or potentially one or more other structural or other problems that may have contributed to the catastrophic failure, launching a rescue shuttle would itself be subject to the same risks as Columbia. We might end up with two orbiters with damaged wings on orbit.

Albion

It'll be interesting to see if this is a systemic problem. It sounds as if it's happened before, but it doesn't seem to have been serious enough to have raised a major warning flag. According to some colleagues of my husband (one of whom was involved in the investigation of the Challenger disaster), one problem is that if a piece of insulation comes off and hits at the right angle, it can cause a domino effect with the tiles and dislodge quite a few of them.

As far as repairing in space is concerned, didn't they try some sort of caulk in a repair kit early on or something rather than carrying spare tiles? And didn't they find in tests that it didn't work? Just not sure where I read that now.

Shadowy Man

I would imagine that if a large number of tiles fell off they would have been able to determine this. In the past, a Keyhole spy satellite has been used to examine the underside of the Space Shuttle, so if they were concerned about it this time, I would imagine they would have done the same thing. The Keyhole might not have been able to spot cracks in the tiles, but it would have been able to tell if tiles were missing.

I haven't heard yet that they looked at the Shuttle with a Keyhole, but I wouldn't be surprised if they did.

Mageth

I believe I remember hearing one of the NASA spokespersons saying the other day that in previous missions, they had tried using ground-based and/or space-based methods to examine the shuttle for damage on orbit and found it not very useful, so they didn't bother doing it this time. They also indicated that they probably couldn't positively detect a single (or possibly even a few) tiles missing using such methods due to the contrast problems (black-on-black). I seriously doubt if they could conclusively detect simple damage to one or a few tiles, either.

Shadowy Man

Yeah, I guess contrast problems could be bad. A Keyhole satellite can resolve about 6 inches on the Earth, from a couple hundred miles up, but I don't know how close one of those gets to the Shuttle, nor do I know how big the tiles are.

Maverick

I found a couple of answers to the questions we were raising in this article.

If, in the midst of its 16-day flight, wing damage had been found to be dire, the only potential--but still unlikely--option would have been the formulation over several days by Mission Control of a profile that could have, perhaps, reduced heating on the damaged wing at the expense of the other wing for an unguided reentry, with scant hope the vehicle would remain controllable to about 40,000 ft., allowing for crew bailout over an ocean.

Maverick

Autonemesis

Here are some images of the shuttle as it passed over California that I don't think have been generally released yet. These were taken from video frames shot by a longtime member of the astronomy club I belong to, and are posted on the club's website: here, here, and here.

WhiteKnight

In a word, tragic. I was actually working in a shuttle mission support room during landing, as the loss of comm stretched out longer and longer.

I've spent the last week poring over the "additional 32 seconds of data", extracting GN&C info for use by the accident investigation teams.

If anyone has questions, I'll try to provide some answers (some I can't provide at this time). My background is in shuttle flight software, but I have a decent familiarity with shuttle systems in general.

WhiteKnight

Jimmy Higgins

How do we know that such things aren't actually normal on re-entry. I mean, if the shuttle was already falling to pieces, about what 20 minutes before Texas, wouldn't have the telemetry have read so?

Mageth

How do we know that such things aren't actually normal on re-entry. I mean, if the shuttle was already falling to pieces, about what 20 minutes before Texas, wouldn't have the telemetry have read so?

No, it's not normal for pieces of the shuttle to come off during re-entry. And the pictures were taken only about 8 minutes before the breakup over Texas, I believe. Telemetry wouldn't record pieces of tile falling off; at most, I think, automated adjustments performed to overcome drag problems caused by any damage would be reported, which I believe is what the telemetry showed either at about this time or a little later.