NASA OKs Shuttle Flight, Despite Heat Shield

Oct. 17, 2007 — -- The debate: Is it safe to fly the Space Shuttle Discovery when three of the panels on its wings have deteriorated?

NASA safety engineers are split over the decision. In the end they were overruled by senior managers at the Flight Readiness Review, which gave the go-ahead for the shuttle countdown to start this weekend. The panels are made of reinforced carbon, coated with silica, which keep the searing heat of re-entry from burning through the space shuttle's skin. Three of the 44 composite panels that help protect the shuttle show evidence of degradation, which was detected by thermo graphic imaging.

STS 120 Discovery is now scheduled to launch at 11:38 a.m. EDT Oct. 23. The mission is the most complicated space station construction mission to date. It will add a new module to the orbiting outpost, and the crew will relocate a truss, a delicate and painstaking three-day process. Five demanding spacewalks are scheduled including one just to practice damage repair techniques.

Space Shuttle Program Manager Wayne Hale says he is comfortable flying with the panels "as is." He admits the decision to fly came after a very spirited debate that lasted four hours. But in the end, he said, "The preponderance of evidence shows an acceptable risk in flying, not a safe risk, but an acceptable risk. There are things we do not understand about this vehicle after 26 years of flying."

What is the worst-case scenario? According to Hale, "The potential is catastrophic loss of vehicle so we have to pay close attention to it."

Hale doesn't believe that is a serious prospect; he believes the wing panels may simply lose more of their protective coating. But he contends NASA is prepared to deal with it during the mission.

"If we find something during the inspection we have a repair technique," said Hale. "What evidence is there we will be in trouble during the actual re-entry? After working through all that, I think the majority of engineers and I decided that there is a good analysis that we could survive even if the worst thing happens to us during re-entry.