Discovery Launch Now Back To Feb. 22

NASA is bumping the launch of shuttle Discovery back to at least Feb. 22 to give engineers more time to perform tests aimed at determining whether lingering problems with critical main propulsion system valves might endanger a seven-member astronaut crew.

Senior shuttle program managers now plan to meet Feb. 13 to review test data and determine whether to press ahead with a flight readiness review on Feb. 18. A Feb. 22 launch date would be 10 days later than originally planned and three days later than the agency's most recent estimate.

Discovery and seven astronauts had been slated to launch Feb. 12 on a mission to deliver a fourth and final set of massive American solar wings to the International Space Station.

That plan was scrapped earlier this week when senior agency executives decided NASA needed more time to analyze potential problems with gaseous hydrogen flow control valves in the orbiter's main propulsion system.

One of three valves aboard Endeavour failed to operate as intended during launch last November on a station supply run.

Similar to small pop-up lawn sprinklers, the valves are key to keeping pressure within the shuttle's 15-story external tank at proper levels during an 8 1/2-minute climb into orbit.

Proper pressure is required to make certain the giant tank doesn't rupture. It's also key to ensuring a steady flow of propellant into an orbiter's three main engines.

Sensors detected higher-than-normal pressures in the liquid hydrogen reservoir inside Endeavour's tank last November. Two other gaseous hydrogen valves compensated and Endeavour zoomed into orbit without consequence.

Post-flight inspections showed the failed valve had cracked. Engineers are concerned that sharp debris could cut into gaseous hydrogen tubing, causing a pressure drop -- and a potential engine shutdown -- in flight.

NASA is conducting tests to see if debris liberated from a cracked valve could rupture gaseous hydrogen tubing. The data gathering and review process will take longer than initially anticipated, so NASA is pushing back its next meeting on the matter until Feb. 13. It had been scheduled for next Tuesday.

ABOUT THE IMAGE: Click to enlarge the photo of shuttle Discovery blasting off last February on a mission to deliver the European Columbus science laboratory to the International Space Station.