Saturday, March 28, 2009

The Shuttle Disaster that wasn't -- Barely

I follow space flight fairly close, but here's a chilling bit of history I wasn't familiar with. 21 years ago, just after the return to flight after the Challenger explosion, the Space Shuttle Atlantis came dangerously close to being destroyed by the same sort of tile damage that later destroyed Columbia.
Except that, in many respects, the tile damage to Atlantis, also caused by an insulation impact during launch, was actually worse than the Columbia accident. More than 700 tiles were damaged, and one tile in a critical area was completely destroyed, resulting in melting in the exposed aluminum underneath.

And because of a communications blackout on the top-secret military flight, NASA remained blissfully ignorant of the damage, even while mission commander Robert "Hoot" Gibson was looking at images of the tile damage and thinking, in his own words, "we are all going to die."

I just read the story on the web site Space Flight Now. Here's the gist of it, with some added insights of my own (based in part on the rather mundane picture from the NASA archives seen above):

In 1988, the second post-Challenger mission, STS-27, was launched with a secret spy satellite on board. 85 seconds after launch, a chunk of insulation broke loose from the nose of the right solid-rocket booster and struck along the right side of Atlantis.

It isn't clear from the story if the discovery of tile damage was accidental, but it appears so, and the astronauts were extremely alarmed by what they saw. The insulation had impacted near the nose, and resulted in a triangular-shaped cone of damage all the way down the right side of the spacecraft, from the nose almost to the rear of the wing. You've read Gibson's immediate reaction above.

But because of limitations on communications, the crew were unable to properly communicate their concerns to the ground. During military missions, strict limits are places on communications with mission control to insure secrecy. Anything that might even remotely reveal information about the payload, its characteristics, purpose, or orbit, are closely guarded. One hard-fast rule in this case was, no video.

Finally, reluctant permission was given to send encrypted video of the damage to the ground. But the encrypted video system was black and white, low resolution, and could only send one frame every three seconds or so.

It's also interesting that the only photo I could find in the searchable NASA photo archives referencing the damage is the one above. It shows the crew attempting to repair a video tape containing the video of the tile damage. Yes, that is a roll of duct tape floating there.

The implication I take from this is that video was recorded (using the shuttle's robot arm) of the damage was recorded on tape in order to be converted into encrypted format and sent back to Earth. Only the tape jammed somehow, and... This is a SNAFU of historic proportions. You can read a million things into the bemused expression on the mission specialist's face at right. I like to think he's something like, "we're f*cking about to die, and it all comes down to duct-tape and a Betamax."

Because of the poor quality video, engineers on the ground thought they were just looking at shadows on the surface of the tile and assured the crew there was no danger. The astronauts knew otherwise, but did not attempt to convince the ground, perhaps unaware of their line of reasoning. It was nothing a little open discussion couldn't have fixed, but apparently the communications restrictions didn't allow for that, or at least, encourage it.

And so, the mission continued as planned, with NASA doing nothing (not that there was a lot that could be done, since no repair tools or materials, besides that duct tape, were carried, nor had even been developed at this point), and the astronauts soldiered on, plauged by doubts that they would survive reentry.

Upon landing, they discovered the damage was even worse than the astronauts had realized. Without the new cameras and extension boom now routinely carried on the Shuttle, there was no way to image the entire underside of the shuttle, including large areas of damaged. In told, more than 700 tiles were damaged, including the missing tile, located under the orbiter's nose, an area subject to high heating. Upon landing, it was discovered that the exposed aluminum under the tile had actually begun to melt.

If it had burned through, a literal torch of plasma would have cut into the shuttle and its fragile systems underneath, quite likely dooming the spacecraft. Perhaps, as with Columbia, one of the first warnings would have been the pressure in the landing gear tires, as heat caused them to expand, and finally explode. Except, the indicator might have been on the front tires, rather than the rear.

It didn't happen though. One bit of luck, the missing tile exposed a mounting plate for an antenna, and so was thicker than the skin only inches away. That one detail may have saved Atlantis and its crew.

Post flight, NASA apparently minimized the damage and the risk to the crew. Secrecy may have been an issue, but it's almost impossible to ignore the potential CYA factor. A near disaster only two flights after Challenger, following what was supposed to be a complete safety overhaul of the program, could have grounded the shuttle again and heads were certain to roll. It's interesting that, even now, there are apparently no photos of the tile damage in the searchable on-line archives, though they exist (Space Flight Now has a few).

Of course, if Atlantis had been lost, the shuttle would have definately been grounded, and it very well could have been the end of the shuttle program, and perhaps American manned space flight. That's one grim alternate universe.

But in another one, NASA learned from the mission and launched an immediate review of the potential for tile damage. Methods might have been developed for routine examination of the tiles during each flight. Improvements might have been made to reduce foam shedding and ice build-up. Repair tools and techniques might have been developed. And in that world, Columbia might have survived, or at least its crew might have been rescued by an emergency launch of a second shuttle.

But that didn't happen.

are their grim alternate reality.

The shuttle is scheduled to be retired next year, and I will miss the capabilities we lose when that happens. But I will not miss the shuttle itself, with its inherent design flaws and dangers. There's no reason that the Constellation system that replaces it shouldn't be far safer for the women and men who fly in it.

Let's hope that's so. Space is a dangerous business, and more people will die in its conquest. But those deaths shouldn't be tragically avoidable, as was the case with Challenger, Columbia, and almost, Atlantis.

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