One of the toughest problems the Ascent Flight Director faced was how to get the crew back home safely if the shuttle engines quit during the launch phase. We studied and worked out procedures and techniques for over thirty years. Single engine failures were automatically handled; it was the multiple engine out cases that were tough. The orbiter is a glider with a terrible life over drag ratio. Many of the situations we just didn’t have enough range to get to a runway. Plopping the crew down in the middle of the Atlantic Ocean was not a satisfactory answer; stretching the glide to make a runway – like Shannon in Ireland – that was a much better solution. The orbiter does a belly flop during re entry to dissipate the energy; this keeps the temperature down on the heat shield; particularly the hottest part of the wing leading edge which is made up of 02 inch thick composite material: reinforced carbon carbon. At 40 degrees nose high, the temperatures there stayed right around 3,000 degrees F for about half an hour. If the nose were lowered, the temperature climbed, but if the wing stayed intact, the lift over drag ratio was much better. During the early 1990’s we worked very hard with the RCC experts to determine exactly how much we could lower the nose, increase the glide, make the runway, and not destroy the wing. For transatlantic aborts, that number was 31 degrees nose high. The recognized expert on the RCC was Dr. Don Curry of Johnson Space Center. He knew everything there was to know about the wing leading edge materials, structure, testing, and capabilities.
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?”
I was hard pressed to disagree. That mindset was widespread. Astronauts agreed. So don’t blame an individual; looks for the organizational factors that lead to that kind of a mindset. Don’t let them in your organization.
After the accident, when we were reconstituting the Mission Management Team, my words to them were “We are never ever going to say that there is nothing we can do.” That is hindsight.
That is the lesson.