NASA managers could decide as early as today whether to try to launch Discovery in March or postpone its International Space Station assembly mission until April.At issue: Whether it's safe to launch the shuttle with suspect main propulsion system valves whose failure - in a worse case scenario -- could trigger catastrophe in flight.
A go-ahead could lead to a launch attempt around March 7. A decision to redesign the valves could lead to a lengthy delay.
NASA must launch Discovery by March 13 to complete its station assembly mission before an already scheduled crew rotation at the outpost. Otherwise, the earliest launch date would be around April 7.
"They're going to finalize the plan," Kennedy Space Center spokeswoman Candrea Thomas said Tuesday.
In either case, NASA contractor technicians today will begin to replace three valves designed to control the flow of gaseous hydrogen from Discovery's three main engines to its 15-story external tank during flight.
About the size and shape of small, pop-up lawn sprinklers, the valves are key to keeping pressure within the tank at proper levels as propellant within it is exhausted at a rate that would empty a backyard swimming pool in 25 seconds.
Too much pressure could trigger a relief valve and dump combustable gaseous hydrogen overboard - a potentially explosive fire hazard. Too little pressure could lead to a premature engine shutdown.
One of the valves on Endeavour failed in flight last November. Extensive tests are being carried out at several NASA centers to determine whether the valves present an unacceptable risk to the shuttle and its crew.
NASA engineers think valves that have flown on fewer flights are less susceptible to failure. The valves being removed from Discovery each have flown 12 times. Two of the replacements have flown four times; the third has flown five times.
Seven Discovery astronauts aim to deliver a set of American solar wings to the station. Launch time on March 7 would be about 10 p.m.
ABOUT THE IMAGE: Click to enlarge and save this awesome photo that shows shuttle Discovery blasting off last June on a mission to deliver the Japanese Kibo science laboratory module to the International Space Station. Tree branches across the pond from Launch Pad 39A here at NASA's Kennedy Space Center frame the fiery liftoff of the shuttle fleet leader on its 35th flight. Photo credit: NASA/Sandra Joseph, Tony Gray, Robert Murray, Mike Kerley.
2 comments:
According to Bill Harwood of CBS they already made the decision to swap out the valves on Tuesday, leading to a launch as early as March 12.
Our understanding is that the current NET date is March 7. NASA managers okayed the valve swap Tuesday and the R&R work begins today.
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