Monday, March 22, 2010

Weekend Valve Tests Pave Way For Discovery Launch-Date Decision

NASA engineers successfully tested helium regulator valves in shuttle Discovery's right-hand Orbital Maneuverimng System pod over the weekend, clearing the way for a decision this week on whether its safe enough to proceed with the planned April 5 launch of an International Space Station outfitting mission.

Discovery and seven astronauts are tentatively slated to blast off from launch pad 39A at 6:21 a.m. April 5, setting sail on a mission to deliver science experiment racks and tons of supplies and equipment to the International Space Station.

That plan, however, hit a snag when a helium isolation valve associated with shuttle steering thrusters failed during a propellant-loading operation at the pad earlier this month. Helium is used to push propellant into the thrusters and keep the system pressurized at proper levels. NASA engineers believe the valve was stuck in the open position.

NASA over the weekend tested helium regulator valves downstream from the isolation valve to determine whether pressure within the system could be maintained at proper operating levels. The tests showed the valves worked as intended.

The balky isolation valve cannot be replaced at the pad. A decision to replace it would prompt a rollback of Discovery back to its processing hangar, and that move likely would cause up to a three-month delay in one of four final shuttle flights before fleet retirement.

Data from the weekend tests will be presented to senior shuttle program managers this week. The issue also is expected to be briefed Friday at a traditional flight readiness review. A firm launch date typically is selected at the conclusion of that review.

1 comment:

Anonymous said...

There's a very good technical overview of this here:

If you read Todd's first if you aren't shuttle technical, and then the NSF article, you'll get a good grasp.