Cryogenic hydrogen fuel tanks for large hypersonic cruise vehicles

•A tank sizing code for hypersonic hydrogen-fueled aircraft is presented.•Different insulation systems for hypersonic hydrogen tanks are assessed.•Foam-load bearing aerogel and foam-fibrous concepts lead to the lightest tank system.•Aerogel, foam-aerogel and foam-fibrous are sensitive to the external wall temperature.

The design of light yet highly insulated cryogenic tanks is a key enabling technology for hydrogen-fuelled flights, especially when operation in the harsh thermal environment associated with hypersonic speeds is envisaged. This paper examines the use of different insulation systems for cryogenic hypersonic tanks. The investigation for a Mach 5 flight shows that a combination of foam and fully load-bearing aerogel blanket leads to the lightest tank, with a gravimetric efficiency of 73%. If the aerogel blanket cannot be strengthened sufficiently so that it can bear the full load, then a combination of foam and fibrous insulation materials gives the best solution with a gravimetric efficiency of 70.3%. This is around 10% better than (non-load-bearing) aerogel or multi-layer insulations. However, the performance of the foam-fibrous insulation is more sensitive to the external skin temperature than that of other insulation materials so that a foam-multilayer insulation system becomes more efficient at speeds beyond Mach 9. This demonstrates that it is critical to make the best use of each material and that proper combinations of materials can considerably improve the performance of the insulation system.