Results Positive On Helium Iso Valve Test

On Launch Pad 39A at NASA's Kennedy Space Center in Florida, technicians completed a test Wednesday to pressurize space shuttle Discovery's Right Reaction Control System's helium tank to verify the overall health of the regulators downstream of the helium isolation valves. Preliminary data shows positive results for the test. Crews then began preparing Discovery for further testing on the system.

The testing was initiated because of an issue that occurred over the weekend while Discovery's aft fuel propellant tanks were being vented in preparation for fuel loading. The Right Reaction Control System, or RRCS, fuel helium tank pressure unexpectedly decreased in unison with the RRCS fuel propellant tank when the fuel tank was vented. This indicates that at least one of the two parallel helium isolation valves is leaking or is remaining in the open position when it is expected to be closed.

The 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.

Also this week, managers are targeting Friday to move Discovery's payload to Launch Pad 39A, starting at 0001 EDT.

There still are a few days of contingency left in the schedule to make the targeted launch date of April 5.

FMI: www.nasa.gov