Chair Force Engineer

Sunday, August 12, 2007

TPS Report

Tile damage on shuttle Endeavour looks much more serious than initially thought. Recent scans of the shuttle's underside show that two tiles have been completely gouged through to the felt layer underneath.

Depending on the tile location, scars of this depth could prove fatal. On STS-27, the mission was saved by a heavy plate being located underneath the damaged tiles. In our current situation, the damaged tiles lie below wing structural members near the right landing gear.

NASA's current options include flying the shuttle back as-is, repairing it and flying it back, or rescue of the crew by another orbiter, accompanied by an unmanned return of the repaired Endeavour. Of these, I think that doing no repairs is probably out of the question. Even if NASA was able to return the shuttle safely, the perceived dangers of doing so would call into question the safety culture that was supposed to have improved after the loss of Columbia.

I also think that a rescue mission is unlikely. While there's supposedly a system for auto-landing a damaged orbiter, I doubt that the agency is very enthusiastic about testing the system during a mission. A rescue mission would also add an additional delay in the ISS completion schedule. Worst-case, a "rescue" mission is a sign to the public that the shuttle program is too dangerous to fly any more missions; it would likely mean the abrupt end of the space shuttle program.

At the same time, NASA has twice exercised the capability to perform minor "repairs" on the shuttle since return-to-flight. While neither the gap filler on STS-114 nor the loose blanket on STS-117 represented a risk to mission safety, they were performed anyway. NASA wants to demonstrate that it will make the additional effort to rule out even tiny threats to astronaut safety. It also wants to show off the repair capabilities that were developed, at considerable expense, in the aftermath of Columbia's loss.

What do I expect to happen? I think that Michael Griffin is going to go on CNN and tell the world that the astronauts are going to repair the damage and bring the shuttle back as scheduled. He's going to express his confidence in the repair techniques that have been developed to fix the thermal protection system. And the astronauts are going to ride the CanadArm extension to the underside of the shuttle, and fill in the gouges with ablative material. With some divine intercession, they'll make it back home in one piece.