The September launch window for the second Space Shuttle return-to-flight mission, STS 121/Atlantis, is unlikely to be met because of engineering changes that have to be made to the external tank (ET).
Minor changes will be made to the wires supplying power to heaters that stop ice forming on the ET. The Teflon jacket on the bipod area heater wire under the foam may provide a mechanism for liquid nitrogen or air to become trapped causing foam loss on ascent, NASA says.
Ice was considered a possible cause for the breakaway of foam that fatally damaged Space Shuttle Columbia. The heaters have been added since the Columbia accident.
“We have to make some minor engineering changes to the tank and we will probably not meet the September window,” says William Gerstenmaier, NASA’s space station programme manager. Gerstenmaier will oversee the ET work. The next launch window is March 2006.
The technical investigation is being led by Dr Rick Gilbrech, NASA’s Engineering and Safety Centre deputy director.
His Tiger Team has already concluded that the three most important areas are the bipod ramp, the protuberance air load (PAL) ramp and the ice frost ramp. It was the loss of foam from Space Shuttle Discovery’s ET-121’s PAL ramp on ascent that caused the suspension of Shuttle flights. The remaining fourth area is the liquid hydrogen acreage area on the ET’s lower half.
- NASA’s Mars Reconnaissance Orbiter (MRO) lifted off from Cape Canaveral, Florida on 12 August on board NASA’s first Lockheed Martin Atlas V rocket. The probe will determine whether long-standing bodies of water ever existed on the planet.
ROB COPPINGER/LONDON
Source: Flight International
