Catastrophic heat load on a solid-hydrogen dewar

The cryogenic limb array etalon spectrometer (CLAES) to be launched on board the NASA Upper Atmosphere Research Satellite will utilize a solid-hydrogen tank, insulated by a high-vacuum and multilayer insulation system. Any damage to the vacuum vessel prior to launch is considered catastrophic. As the sudden heat load causes the pressure to rise in the dewar, a burst disk in the emergency vent line will rupture to allow the escape of vaporized cryogenic fluid. For a given vent line system with a given stagnation condition at the inlet, there is a peak flow rate such that the flow will be subsonic throughout the line. Using this peak flow rate, the calculation of the dewar pressure profile depends on an accurate prediction of the dewar heat load. A catastrophic venting test was conducted on a subscale dewar.