NASA: Shuttle flights still risky

Griffin says launch decision near
BY CHRIS KRIDLER FLORIDA TODAY
Rollout delayed
Space shuttle Discovery's roll to the launch pad has slipped to early Tuesday morning, in part because managers want to move its cargo to the launch pad ahead of time -- Monday -- and partly because Discovery was mated to its new fuel tank later than expected.Another fuel tank scheduled to leave the Michoud Assembly Facility in Louisiana on Thursday was held up because of Tropical Storm Arlene. It was supposed to travel by sea and arrive at the Cape early next week.
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CAPE CANAVERAL - NASA said Thursday it had made progress in returning the shuttles to flight, though the orbiters still are vulnerable to disastrous hits by debris, a risk the agency accepts.
In an introduction to an update of the agency's return to flight plan, new Administrator Mike Griffin said NASA would not rush to flight, though it was close to making an "informed decision" about launching shuttle Discovery in July.
"Human space exploration is not and will never be without risk," he wrote. "However, I am convinced that this Nation and this Agency can execute the bold exploration agenda set forth by the President as safely as humanly possible."
The 288-page report summarizes how NASA has attempted to address the recommendations of the Columbia Accident Investigation Board.
Among other topics, the report goes into detail on efforts to make the shuttles more resistant to debris hits and heat. There will be more protection for vulnerable wing panels, the landing gear area, selected panels and side windows.
The report also sums up NASA's evaluation of the danger posed by foam and ice as they are shed by the external fuel tank. Foam from Columbia's tank hit the orbiter during launch, leading to a breach that became fatal when the ship tried to reenter the atmosphere.
Heat-shield tiles are easily damaged, but even when they take a hit, they stand up to heat well, the report concluded. On the other hand, reinforced carbon-carbon, like that on the wings' leading edge, is tougher but is open to disaster even if slightly damaged.
The wing leading edge is still vulnerable to ice and impacts of foam from the liquid oxygen flange area near the middle of the fuel tank, the report concludes. The orbiter's nose cap and chin panel would be vulnerable to the same foam impacts.
This "worst-case environment is very unlikely to occur," the report said.
When the shuttle returns to flight, "there will still be the potential for foam to cause damage to tile that exceeds safe entry limits . . . but this potential has been significantly reduced."
NASA has accepted this risk for the shuttles' return to flight, the report said. It admits that improved testing on the ground still "will not allow us to verify the precise condition of foam and RCC."
NASA is concluding its debris analysis before the flight readiness review at the end of June.
Discovery will carry only limited tile repair capability.
Contact Kridler at 242-3633 or ckridler@flatoday.net