NASA still has no way to detect voids without damaging the foam. "We're developing techniques, with very promising results," said Marshall's Neil Otte, NASA's chief engineer for the external tank, but these will not be ready for a March return to flight.
"This is not an easy problem," Otte said in a telephone interview. "We're taking a system that was designed 25 years ago and we're defining and applying new requirements. What you would like to do is set out your requirements, and then engineer the system."
A bulldozer sits atop debris from the Kennedy Space Center's Vehicle Assembly Building at Cape Canaveral, where hurricanes Frances and Jeanne tore panels from the building.
(Peter Cosgrove -- AP)
Because there is no fail-safe method to eliminate debris, the investigation board recommended that NASA develop onboard inspection and repair capabilities for both the ceramic tiles that insulate the belly of the orbiter and the leading edge material on the wings.
Delays in developing a boom to inspect the orbiter's underside caused O'Keefe earlier this year to move the projected return to flight from its original date this fall to the current March time slot. The boom "is right on schedule now" for a November delivery date, Space Shuttle Program Manager William W. Parsons said in a telephone interview. "We will be able to inspect all the areas of the orbiter that we will need to look at."
The task group's Cuzzupoli agreed that the boom no longer presents "significant technical challenges."
Prospects are not as bright, however, for onboard repair. O'Keefe cited the shuttle's inability to make its own in-flight repairs as the main reason for canceling a mission to do maintenance on the Hubble Space Telescope.
Instead, the shuttle will fly only to the international space station, where it can use the station's robotic arm to help with any needed repairs. Engineers at the Johnson Space Center have developed an applicator for the caulking that astronauts would use to patch the ceramic tile, and engineers at the Langley Research Center, in Hampton, Va., are testing the caulk.
Repairing the reinforced carbon-carbon, however, is another matter. Developing onboard capability to repair any size damage is "years out," Parsons said. But "when it comes to smaller holes and cracks, we have a lot of optimism."
The hope is to develop a gun that astronauts would use to spread a special caulking material across a crack or small hole in the shielding's carbide coating, so when the orbiter's leading edge heats up during reentry, the caulk would melt into the crack. "It's still in the development phase, and I couldn't tell you how far we'll get," Parsons said. "I can't tell you if we'll have a certified repair capability."
Failure to plug a large hole in reinforced carbon-carbon would risk a repeat of the Columbia disaster, so NASA, apart from the investigation board recommendations, is exploring the possibility of allowing a shuttle crew to seek "safe haven" aboard the space station for some as yet unspecified time period until a second shuttle could pick them up.
In June, a pair of NASA reports painted a grim picture of the station's ability to support a seven-member shuttle crew and the two-member station team long enough for a shuttle to reach them.
The picture deteriorates further if return to flight slips past the current March date, because the space station's dwindling supplies and support capabilities will be further depleted as time passes.
Parsons said NASA has been deliberately "erring on the pessimistic side" and will seek to "maximize our capability" in coming months by shipping equipment and supplies to the station aboard Russia's relatively diminutive Progress cargo spacecraft.
"We have people that are looking at this, and as we get closer to launch they'll sharpen their pencils more and more," Parsons said. "We'll take a look, and the reality will be what it will be."