"The foam did it," says board member Scott Hubbard, and most of the Columbia Accident Investigation Board's recommendations are directed at identifying the cause, and preventing a repeat, of the Columbia accident and returning the Space Shuttle to flight. The 15 near-term return- to-flight recommendations "need to be done immediately", says board chairman Hal Gehman. The mid-term (three to 15 years) continuing-to-fly recommendations "are more fundamental and harder, but more important", he says.
Gehman says the return-to-flight recommendations are designed to "understand and reduce the debris that is shed by the external tank; toughen the orbiter so that it can fly through debris without damage; and inspect and repair the orbiter in orbit if it is damaged". He says the board has left a fourth step to NASA, that of enhancing crew survivability if the damage cannot be repaired.
NASA must initiate an aggressive programme to eliminate all external-tank debris shedding, but the board has not made the complete elimination of debris a condition for return to flight. "It is unreasonable to require for return to flight that they eliminate all debris shedding. There will always be some ice," says Gehman. "What we want is a programme aimed at understanding the foam, with the intent of eliminating shedding eventually."
The board has made development of a thermal-protection system (TPS) on-orbit inspection and repair capability a requirement for return to flight. NASA must also improve its launch and in-orbit imaging capability to help detect debris and damage, and in the longer term develop accurate computer models to evaluate TPS damage from debris impacts and establish damage thresholds for on-orbit inspection and repair.
Self-imposed schedule pressures tied to completion of the International Space Station contributed to the accident, the report says. The board recommends that, for return-to-flight, NASA adopt and maintain a Shuttle flight schedule consistent with available resources. The mission management team also requires training in safety contingencies involving potential loss of a Shuttle or crew.
Source: Flight International
