NASA Gears Up For Shuttle Valve Swap

NASA is gearing up for a valve swap deemed critical to plans to launch Discovery Feb. 12 on a mission to deliver a final set of American solar wings to the International Space Station.

Now poised on launch pad 39A at Kennedy Space Center, Discovery is scheduled to blast off at 7:32 a.m. Feb. 12 with seven astronauts aboard, setting sail on a mission to haul up the final segment of the station's lengthy central truss.

Standard launch preparations are continuing without major problems, but NASA contractor technicians still must install three refurbished flow control valves that arrived at KSC this morning.

NASA program managers ordered the change-out after gaseous hydrogen flow control valves failed to work properly during the launch last November of shuttle Endeavour.

Similar to pop-up lawn sprinklers, the poppet valves are critical to keeping pressure within the external tank's liquid hydrogen reservoir at proper levels as the shuttle is thundering toward orbit and propellant in the tank is fed into the orbiter's three main engines.

One of the three GH2 flow control valves on Endeavour failed to operate as intended during ascent, but the other two compensated and the spaceship zoomed into orbit.

NASA nonetheless wants to make certain that Discovery is equipped with three good GH2 flow control valves. The valve swap must be completed and the new poppets must pass subsequent testing for NASA to remain on track for the planned Feb. 12 launch.

NASA contractor technicians also are retesting a wire harness in the rear engine compartment of the orbiter that failed an earlier checkout. The harness routes computer commands to the pyrotechnic devices used to separate the orbiter from its launcher platform, solid rocket boosters and external tank during flight.

Senior NASA managers, meanwhile, will meet at KSC next Tuesday for an executive-level flight readiness review. Assuming the valve swap-out and other prelaunch work goes as planned, NASA is expected to firm up the Feb. 12 launch date at the conclusion of that meeting.

ABOUT THE IMAGES: Refresh this page to see the latest still images from live video feeds in the Launch Complex 39 area at Kennedy Space Center. The view on the left is from a camera atop the Vehicle Assembly Building. The image on the right is from a camera at launch pad 39A. Click to enlarge either photo. You can see Discovery's external tank poking up over the Rotating Service Structure in the image on the right.