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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