NASA Targets March 11 For Discovery Launch

NASA is pressing ahead with plans to launch shuttle Discovery next week and is moving its target launch date up a day to Wednesday. The date is expected to be firmed up at a flight readiness review on Friday.

The decision followed an all-day review of extensive testing and engineering analyses prompted by the failure of a critical main propulsion system valve during Endeavour's successful launch last November.

Managers "feel confident enough that they can press ahead with a Flight Readiness Review based upon all of the testing and analysis," said Kennedy Space Center spokesman Allard Beutel.

At the end of the meeting, NASA shuttle program manager John Shannon polled all members of a board responsible for making key program decisions, one that includes independent safety offices.

"It was a unanimous decision by all parties to press ahead," added Kyle Herring, a spokesman at NASA's Johnson Space Center in Houston.

Liftoff time on Wednesday would be 9:20 p.m.

NASA must launch Discovery by March 13 to complete its planned 10-day stay at the International Space Station and then depart before the March 26 launch from Kazakhstan of an already planned station crew rotation mission. Otherwise, the shuttle launch would have to be postponed until around April 7.

Seven astronauts aim to fly Discovery on a mission to haul up a fourth and final set of American solar wings to the International Space Station.

Discovery mission commander Lee Archambault and his crew will go into quarantine tonight at Johnson Space Center in Houston to protect the option to fly on March 11. The crew includes pilot Tony Antonelli and mission specialists Joseph Acaba, Steve Swanson, Richard Arnold and Koichi Wakata of the Japanese Aerospace Exploration Agency.

Wakata will repplace current station engineer Sandra Magnus, who will return to Earth on Discovery. He will be the first Japanese astronauts to serve a long-duration tour on the outpost.

The crew will arrive at Kennedy Space Center about 3 p.m. Sunday. A three-day launch countdown will begin about 7:30 p.m. that night.

One of three gaseous hydrogen flow control valves failed during Endeavour's successful launch last November.

About the size and shape of pop-up lawn sprinklers, the poppet valves regulate the flow of gaseous hydrogen into the shuttle's external tank during the nine-minute flight into orbit. The gaseous hydrogen keeps pressures within the tank at proper levels as propellant within it is exhausted by the ship's three main engines.

Too little pressure could cause an engine shutdown in flight. Too much pressure in the tank could force open a separate relief valve that would dump combustible gaseous hydrogen overboard - a potentially explosive fire hazard.

Post-flight inspections on the failed Endeavour valve showed a piece of its lip cracked off. Engineers had feared debris could rupture gaseous hydrogen pressurization lines that run between the shuttle's main engines and the external tank.

Of particular concern are 90-degree bends in the lines about five inches from the engines. High-velocity impact tests have shown that debris could puncture the lines in that area in a worst-case scenario.

Some engineers thought the area should be reinforced as a result, but managers decided that work would not be required to press ahead with Discovery's launch. Tests have shown three valves installed on Discovery earlier this week have no discernable flaws, so no debris large enough to cause critical damage could be created, the analyses show.

"We've installed the best crack-free poppets -- at least to the limit of detection capability that we have," Herring said.

NASA also has been running tests designed to determine the effectiveness of inspection techniques the agency uses to detect microscopic cracks in the valves.

The agency traditionally has used electron microscopy and dye penetration tests to detect cracks. But extensive analyses of valves in inventory have shown that cracks have gone undetected after those tests.

NASA in the last several weeks has been using a non-destructive technique known as an eddy current test to detect cracks. The process uses electromagnetic induction to detect subtle changes in current that are indicative of cracks. Cracks as small as 1/20,000th-of-an-inch can be detected.

A growing confidence in the effectiveness of eddy current testing led to the decision to press ahead with a formal, executive-level flight readiness review on Friday. The flight rationale that will be presented will note that any cracks on the valves on Discovery would be so small that they could not possibly liberate any debris that would puncture a pressurization line.

ABOUT THE IMAGE: Click to enlarge and save the awesome NASA image of shuttle Discovery rolling out to Kennedy Space Center's launch pad 39A in January. You can also click the enlarged image to get a bigger, more detailed view. Photo credit: NASA/Troy Cryder.