Worries must be resolved before decision is made on July launch window
A propellant loading test with Space Shuttle Discovery on 20 May failed to satisfy concerns over two external tank components that were raised during the launch-pad tanking exercise in April. Worries remain about sensors in the liquid-hydrogen tank and these must be resolved before launch of the STS 114 return-to-flight mission.
The sensors command Shuttle main engine cut-off at fuel depletion. Also, a pressure-relief valve in the hydrogen tank opened and closed 13 times during the tanking test, as it did in April. This is considered the maximum number of times the valve can operate. Inspections are also planned to look for potential cracks in the landing gear after defects were found in the orbiter Atlantis.
A test of Discovery's auxiliary power unit is planned before the Shuttle stack is rolled back into the Vehicle Assembly Building at Kennedy Space Center, where it will be fitted with a new set of solid rocket boosters and the modified external tank originally scheduled to fly on the second RTF mission, STS 121. After Discovery's second roll-out in mid-June, there will be another tanking test before the decision on whether to stick to the 13-31 July launch window.
Meanwhile, NASA administrator Mike Griffin says there is no chance of delaying the Shuttle's planned retirement in 2010, especially as work on the Crew Exploration Vehicle is being accelerated.
TIM FURNISS/LONDON
Source: Flight International
