Wednesday, August 26, 2009

Live At KSC: Tests Tonight Should Tell Shuttle Tale

A relatively short series of tests tonight should yield results that will either put NASA on track for the launch of shuttle Discovery Friday or push its International Space Station mission back until October.

Discovery and seven astronauts are tentatively set to launch at 12:22 a.m. Friday. There would be a second opportunity to set sail for the orbiting outpost at 11:59 p.m.

The weather forecast for launch is favorable. There is a 70 percent chance conditions will be acceptable for launch. The prime concerns are a chance of electrically charged clouds around the launch pad, thunderstorms within 20 nautical miles of the shuttle runway and high seas for solid rocket booster recovery.

Check out the details in this Official Forecast from the U.S. Air Force 45th Space Wing Weather Squadron. The wing provides tracking, range safety and weather forecasting services for all launches from Kennedy Space Center and Cape Canaveral Air Force Station.

NASA engineers at this hour are inerting shuttle Discovery's external tank, which was drained of about 500,000 gallons of liquid hydrogen and liquid oxygen after a launch scrub on Tuesday. The process ensures all flammable gas has been purged from the tank.

A main propulsion system liquid hydrogen fill-and-drain valve appeared to fail near the close of external tank propellant-loading operations. The eight-inch-diameter valve plays a key role in enabling the offloading of liquid hydrogen after a scrubbed launch attempt. It also is critical to dumping excess liquid hydrogen from the main propulsion system once the shuttle reaches orbit.

The valve appeared to fail to close properly. However, engineers think a sensor designed to indicate valve closure might have failed instead of the valve. So to test that theory, NASA will cycle the valve open and shut five times. A pressure decay test of an associated manifold also will be performed.

The tests are scheduled for around 5:30 p.m. The data from the tests should be available for review around 8:30 p.m.

If the sensor is the culprit, then NASA could press ahead with plans to launch Friday. If any more invasive work is required -- such as removing and replacing the valve -- then the launch likely would slip until mid-October.

NASA officials say they would yield to previously scheduled Japanese and Russian missions to the station. The next opportunity for Discovery in that case would come on Oct. 17.


Anonymous said...

We're just not giving them enough money. Cut Social Security $20.00 a month and give it to NASA. The Shuttle will be old enough for SS soon.

Anonymous said...

TS Danny is supposed to be going by on Friday. Wonder how that affects the booster recovery with the rough seas. Any launch criteria for that situation?

Anonymous said...

Downrange sea states are a consideration, but there is no hard and fast rule:

"A downrange weather advisory shall be issued by the Shuttle Weather Officer to the Mission Management Team for their consideration if the wind in the solid rocket booster recovery area is forecast to exceed 26 knots during retrieval operations. Seas in excess of Sea State 5
(8-13 feet) may also be a factor considered by the Mission Management Team"

Conor said...

Does it matter at this stage of the game? Would any of the components of Discovery's SRBs ever fly again with only six more flights on the manifest?
Launching Discovery by the end of the month seems more important to me than the safety of the boosters. Although I suppose they could be a hazard to shipping if not retrieved.