Decision to load hypergolic propellants off-line expected to pose safety challenges
NASA has decided to load the Orion crew launch vehicle with its hypergolic fuels before it reaches the pad and before it reaches the Kennedy Space Center's vehicle assembly building for stacking on to the Ares I crew launch vehicle. The decision could pose safety challenges during ground processing.
Hypergolics are fuels and oxidisers that remain liquid at room temperatures and pressures and ignite on contact, requiring no ignition source. But they are toxic and require special handling. Common hypergolic fuels are hydrazine, monomethyl hydrazine and unsymmetrical dimethyl hydrazine. The oxidiser is usually nitrogen tetroxide or inhibited red-fuming nitric acid.
"They have committed to off-line hypergolic servicing of the Orion with a back-up capability at the pad, so I expect to see some early operational and safety problems with Orion's 9,000kg [20,000lb] of hypergolics being stored and handled in the assembly building," says a NASA space programme source. "They are, in effect, treating Orion like they would a very large unmanned probe that is normally loaded offline before installation. Only the quantities involved are significantly higher and the manned complexity of the ship requires considerably more testing and interface verifications after installation," he adds.
The decision is part of the requirements baseline established by NASA for ground systems at Kennedy to support the Constellation programme. Despite completing its ground systems review, the space agency has delayed an industry day that was to provide information on the planned July 2009 award of a contract for ground processing services. With the request for proposals to be published in early September, NASA had planned an industry day in early April, but it was cancelled and, almost two months later, no new date has been set.
The Kennedy ground systems requirements baseline was set after an examination of the capabilities needed to support Ares launcher, Orion crew vehicle and Artemis lunar lander integration and ground processing launch processing infrastructure, including the vehicle assembly building, launch pads and control centre vehicle protection systems checkout and control crew safety and emergency egress and fault tolerance requirements.
After completion of all of the Constellation programme's project-level assessments, an integrated review in late May will be used to update and synchronise all of the programme's baseline requirements.
Source: Flight International
