NASA internal documents suggest that the US space agency is playing down risks of damage from shuttle debris that led to the 2003 disintegration of Columbia in order to resume shuttle flight quickly, The New York Times reported Friday.
The documents, given to the newspaper by the National Aeronautics Space Administration (NASA) employees who declined to be named, "show at least three changes in the statistical methods used in assessing the risks of debris like ice and insulating foam striking the shuttle during the launching."
The move has triggered a debate within NASA about whether the changes are a reasonable reassessment of the risks of flight or whether they abandon long-established rules to justify a quick return to space, the newspaper reported.
According to the newspaper, one presentation states that lesser standards must be used to support accepting the risks of flight, "because we cannot meet" the traditional standards.
A trunk of insulation foam that fell off from Columbia's external fuel tank damaged the shuttle's left wing, leading to the shuttle disintegration during its re-entry in February 2003.
NASA has redesigned the fuel tank to reduce the size of debris possible to fall off as a safety improvement measure in line with recommendations of the Columbia accident investigation board.
Experts who have read the documents told the Times that they do not suggest that the shuttle Discovery, which is scheduled to be launched from Cape Canaveral, Florida, on May 22, is unsafe.
The Times reported that several tables contained in the internal documents show no tolerance for ice impact from several sources under a worst-on-worst environment. Even the best-estimate environment does not meet the impact tolerance goals without lowering standards.
NASA is completing its analysis of 177 possible debris sources and is about to present the data to the task force overseeing the return-to-flight preparations.
NASA's new chief, Michael Griffin, has said that NASA may resume in May the first shuttle flight since the Columbia disaster no matter what the task force concludes on the flight safety.