Problem Arose During Preparations For Fuel Loading

Engineers met at NASA's Kennedy Space Center in Florida Monday to discuss options following an issue that arose while venting space shuttle Discovery's aft fuel propellant tanks in preparation for fuel loading during the weekend.

The Right Reaction Control System, or RRCS, fuel helium tank pressure unexpectedly decreased in unison with the RRCS fuel propellant tank. At least one helium isolation valve is leaking or is remaining in the open position when it is expected to be closed.

NASA determined that two helium system regulators, a primary and a secondary, will be tested to verify they are functioning correctly. The regulators are "downstream" of the isolation valves, and help to maintain helium pressure to the fuel tank. Knowing whether the regulators are operating correctly is a key factor for managers who must decide whether to launch with the errant condition of the isolation valves. The test is expected to occur late this week once a ground support equipment test panel has been calibrated. The helium system will be brought to flight pressure and engineers monitoring the panel will ascertain whether the regulators function properly.

Currently, the rotating service structure rotation will be delayed to no earlier than Tuesday. Managers also are discussing when to take the STS-131 payload to the launch pad and whether to continue with its installation. As of now, the payload will go to the pad Wednesday. Launch still is targeted for April 5.

At NASA's Johnson Space Center in Houston, the STS-131 astronauts will spend downtime with their families during spring break this week.

FMI: www.nasa.gov