Two senior NASA officials who voted not to proceed with a July 1 launch of the space shuttle Discovery said Monday that astronaut safety is foremost in their minds, and that the upcoming spaceflight holds no threat to the STS-121 crew's safe return.
"Crew safety is our first and most important concern," read the statement prepared by NASA's chief engineer Christopher Scolese and Bryan O'Conner, a former astronaut and the space agency's chief safety and mission assurance officer. "We believe that our crew can safely return from this mission."
NASA officials said in a June 17 briefing that Scolese and O'Conner offered dissenting opinions on whether the Discovery orbiter was ready for a July 1 launch. The upcoming spaceflight will mark NASA's second shuttle flight since the 2003 Columbia accident and follows the STS-114 mission that launched last year.
William Gerstenmaier, NASA's associate administrator of space operations, said in the June 17 briefing that the dissent revolved primarily around a series of foam-covered ramps that prevent ice from building up on brackets that connect cables and pressurization lines to the exterior of Discovery's external tank. Scolese and O'Conner voted to delay the STS-121 launch until engineers developed a proper fix for the ice frost ramps, he added.
On Saturday, NASA decided to launch Discovery's STS-121 mission on July 1 knowing that some of the 34 ice frost ramps on shuttle tanks could shed foam debris during launch. In the past, top shuttle program officials have said that ice frost ramp foam debris could inflict serious damage to an orbiter and future fixes are planned for the problem.
But NASA chief Michael Griffin said Saturday that - given NASA's ability to inspect spacecraft in orbit, some rudimentary repair methods, and the option to keep astronauts aboard the International Space Station (ISS) in an emergency - ice frost ramp foam should not lead to a crew-loss situation for the STS-121 mission.
Scolese and O'Conner added in their statement that, the orbiter aside, ice frost ramp foam loss should not pose a threat to crew safety.
"We both feel that there remain issues with the orbiter - there is the potential that foam may come off at time of launch. That's why we feel we should redesign the ice/frost ramp before we fly this mission," the statement reported. "We do not feel, however, that these issues are a threat to safe return of the crew. We have openly discussed our position in the Flight Readiness Review - open communication is how we work at NASA."
The statement by Scolese and O'Conner reported that all different engineering positions were heard during NASA's two-day STS-121 mission Flight Readiness Review (FRR). The statement also reported that the FRR meeting's board members and Griffin made an "informed decision and the agency is accepting this risk with its eyes wide open."
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