NASA engineers are testing a leaky helium valve on thespace shuttle Discovery to see if the shuttle can still launch to theInternational Space Station next month or if it must stand down for repairs.
Discovery is slated to launch a crew of seven astronautson a cargodelivery mission to the space station on April 5, but shuttle techniciansmust determine the spacecraft is ready to fly in the next few days to maintainthat launch target.
The helium leak was detected Friday as engineers ventedDiscovery?s two aft-mounted thruster systems while preparing to load them withpropellant. That was when fuel helium tank pressure on Discovery?s right sidereaction control system unexpectedly dropped, suggesting that one of twocritical isolation valves is either leaking or stuck open when it should beclosed.
NASA spokesperson Allard Beutel told SPACE.com thatengineers were able to complete the fueling operation after manually closingthe valves.
?We physically, manually closed the isolation valves, sowe know they work,? Beutel said. NASA wants to be sure the valves will work asdesigned once the shuttle Discoveryreaches space, he added.
Discovery?s aft thrusters are located to either side ofthe shuttle?s tail near pods that contain larger engines. They include reactioncontrol thrusters for fine adjustments in space.
Engineers plan to test two helium system regulators,which are downstream of the faulty valve, to help make a decision on whether arepair will be required.
?Knowing whether the regulators are operating correctlyis a key factor for managers who must decide whether to launch with the errantcondition of the isolation valves,? NASA officials said in a statement.
That test is slated for later this week, they added.
When NASA hauled Discovery to the launch pad on March 3,the space agency had more than a week of cushion time to handle any unexpectedglitches and still maintain an April 5 launch target. There are still a fewdays remaining in that cushion, Beutel said.
The valve tests have delayed plans to deliver Discovery's cargo to the shuttle's seaside launch pad at the Kennedy Space Center in Florida. That move was slated for this morning, but has been rescheduled for early Friday, Beutel said.
Top NASA shuttle managers are also slated to meet nextweek to select a firm launch target for Discovery, but that decision may hingeon the result of this week?s tests.
Discovery?s 13-day mission to deliver fresh supplies,refrigerator-sized racks of science equipment and other gear is one of NASA?sfour finalshuttle missions before the space agency retires its three-orbiter fleetlater this year.
NASA has launched one shuttle flight this year ? lastmonth?s two-week flight aboard Endeavour ? to deliver a new room and stunning observationdeck to the International Space Station.
Any delay to this mission could have a ripple effect downthe line for the remaining three missions, which are slated to launch May 14,July 29 and Sept. 16.
Discovery is also currently scheduled to make that finalspaceflight, which will deliver supplies and a permanent cargo module toessentially serve as a spare closet for space station astronauts.
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