Agency says emergency thermal protection fixes must undergo development tests in orbit before certification
NASA could decide later this month which thermal protection system (TPS) repair techniques will be tested in orbit on the first two Space Shuttle return to flight (RTF) missions.
The space agency does not expect to have a certificated repair kit available for the first flight, but does not believe this should delay the launch, set for May.
"We are working to conduct development tests on orbit," says Bill Readdy, associate administrator for space operations.
"We are reluctant to use a repair on the first flight until we demonstrate it first, bring it back and test in the arcjet [re-entry simulator]." There is also some debate within the agency on which repairs to test in orbit.
The Columbia accident investigation board (CAIB) recommended NASA develop a practicable capability to make emergency repairs to the widest possible range of TPS damage before return to flight. Two years after Columbia's disintegration, repairs for both tiles and reinforced carbon-carbon leading edges are still under development.
"We are bound by the CAIB to work on repair techniques," says Readdy, but NASA believes it cannot certificate a repair before first demonstrating it in orbit.
The task group overseeing NASA's implementation of the CAIB's recommendations also believes the lack of a certificated repair kit should not hold up the return to flight.
The repair kit remains one of the final issues to be resolved before the Shuttle can be cleared to fly again. In the absence of approved repairs, NASA plans to use the International Space Station (ISS) as a safe haven for the Shuttle crew in case of TPS damage on either of the RTF missions.
"Everything appears tracking in the direction that we will meet the CAIB recommendations to the best of our ability at return to flight," says departing NASA administrator Sean O'Keefe, unveiling a NASA budget request for fiscal year 2006 that funds five Shuttle assembly flights to the ISS.
NASA expects to decide by the third quarter the number of Shuttle flights needed to complete assembly of the ISS configuration agreed with its international partners. The current plan is 28 flights, but NASA wants to reduce this.
"Are there ways to accomplish the mission without needing the Shuttle? For logistics, yes," says Readdy, citing Europe's Ariane-launched automated transfer vehicle (ATV) and its Japanese equivalent, the H2-launched HTV.
NASA has earmarked $160 million in FY2006 to begin buying commercial crew and cargo services for the ISS, and a request for proposals is expected in the third quarter. "We are ready to move on alternatives for logistics," says Readdy.
He envisages a two-tier system, the first tier for high-value, complex cargo and restricted to the ATV, HTV or similar module.
The second tier, for "more mundane, easily replaceable" cargo such as food and water, would be open to new commercial launch providers. "It is hard to meet the maturity gate to compete. We are trying to eliminate that as a barrier," he says.
GRAHAM WARWICK / WASHINGTON DC
ADDITIONAL REPORTING BY TIM FURNISS
Source: Flight International
