Posted on Friday, February 08, 2013 - 12:01 am:

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During the last week of Columbia�s flight, I was in Houston and attended the MMT on Monday morning in person. Calvin Schomberg of JSC�s Engineering organization gave the discussion of preliminary results on possible damage to the shuttle tiles from the ascent debris strike. Much has been made of this analysis in the CAIB report. There were flaws in the analysis, but post accident testing showed that the bottom line was correct: a glancing foam strike on the underside of the left wing would have damaged the soft thermal tiles but probably not to the point at which fatal heat would reach the interior of the wing. Calvin was a recognized expert on the shuttle tile system. After discussion of other minor issues on the mission and the status of the ongoing experiments, the MMT was adjourned.

In the hall outside the meeting, I encountered Don Curry. I asked him if there was any concern with the RCC. His reply �Oh, the RCC is tough stuff. You know during qualification testing we even shot ice at it. The RCC is OK.� That was good enough for me. The expert had spoken. It never occurred to me to ask anyone else; nor did the question come up formally during the MMT review.

And of course, the accident investigation � all those pieces picked up in East Texas � showed that the tiles were intact; the RCC had taken the strike � and had broken.

So all the discussion in the accident report about the flaws in the tile analysis are simply not applicable. We were working the wrong problem. The hard RCC panels in the very front of the wing, not the soft silica thermal tiles on the bottom of the wing were at issue.

I spent a lot of time the early part of the week in the Mission Evaluation Room where the engineering analysis teams were headquartered; I sat through more than one MMT; and I visited with my fellow Flight Directors in the Flight Control Room. All was quiet, nobody talked about any serious concerns about anything; just the usual logistical administrivia of getting on with a routine shuttle mission.

Jon Harpold was the Director of Mission Operations, my supreme boss as a Flight Director. He had spent his early career in shuttle entry analysis. He knew more about shuttle entry than anybody; the guidance, the navigation, the flight control, the thermal environments and how to control them. After one of the MMTs when possible damage to the orbiter was discussed, he gave me his opinion: �You know, there is nothing we can do about damage to the TPS. If it has been damaged it�s probably better not to know. I think the crew would rather not know. Don�t you think it would be better for them to have a happy successful flight and die unexpectedly during entry than to stay on orbit, knowing that there was nothing to be done, until the air ran out?�

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