Spaceflight Now

On-orbit tile, RCC repair required to resume flights
Posted: August 26, 2003

NASA must develop the capability to repair damaged heat shield tiles in orbit, as well as cracks or breaches in the reinforced carbon carbon panels making up the shuttle's wing leading edges, before space shuttles return to flight, the Columbia Accident Investigation Board says.

In the board's final report, released earlier today, the CAIB made 29 recommendations, 15 of which are to be implemented before the next shuttle flight. Because of the way the report marked those recommendations, using boldface red type "RTF" tags, one five-paragraph recommendation was misinterpreted by some readers who initially thought RCC repair capability was not a requirement for return to flight.

At a news conference and later in an interview with CBS News, board chairman Harold Gehman left no doubt: NASA must be able to repair damage to both tiles and RCC panels before the next shuttle takes off.

"Recommendation 6.4.1 contains four provisions, all of which are return to flight," he said.

That is a significant requirement. While NASA is expected to have a working tile repair technique in hand within a few months, developing a reliable RCC fix is a much greater challenge because of the nature of the material and the extreme 3,000-degree temperatures it is exposed to during re-entry. Some observers believe that requirement alone will push the next shuttle flight into the summer 2004 timeframe if not later.

"We think that's probably the long pole in the tent," Gehman said in an interview. An innovative technique used by Thiokol to repair carbon composite rocket nozzles shows promise and other techniques are under study as well. But repairing breaches in RCC panels is, at present, a long way from reality.

In any case, here is the recommendation in question:

"For missions to the international space station, develop a practicable capability to inspect and effect emergency repairs to the widest possible range of damage to the Thermal Protection System, including both tile and Reinforced Carbon-Carbon, taking advantage of the additional capabilities available when near to or docked at the International Space Station.

"For non-Station missions, develop a comprehensive autonomous (independent of Station) inspection and repair capability to cover the widest possible range of damage scenarios.

"Accomplish an on-orbit Thermal Protection System inspection, using appropriate assets and capabilities, early in all missions.

"The ultimate objective should be a fully autonomous capability for all missions to address the possibility that an International Space Station mission fails to achieve the correct orbit, fails to dock successfully, or is damaged during or after undocking. [RTF]"