A critical review of cryogenic hydrogen storage and fuel-system integration for aviation

Airworthiness qualification of new materials, manufacturing processes and cryogenic system architectures can require 5–9 years after conception, meaning that the generation of certification evidence, rather than material performance, can become the rate-limiting step in translating innovations into aircraft. Liquid hydrogen (LH2) is attractive for medium- and long-range aviation because of its high specific energy, approximately 120 MJ kg−1, however hydrogen aircraft cannot be realised through fuel substitution alone. This review examines cryogenic hydrogen storage and fuel-system integration for aviation, arguing that LH2 tanks should be treated as active cryogenic supply systems embedded within the aircraft. It synthesises thermodynamic, fluid, material, structural, safety and certification challenges, drawing on aerospace, maritime and industrial cryogenic systems. A central finding is that desirable design directions are often antagonistic. A heat leak of only 1 W corresponds to approximately 2.24 mg s−1 of hydrogen boil-off, yet reducing heat ingress through more advanced insulation can increase mass and system complexity. Similarly, excess ullage improves pressure-control margin but reduces useable liquid volume, and sloshing controls may introduce thermal bridges. The review reframes aviation LH2 design as a coupled problem requiring aircraft-scale transient validation, full-field diagnostics, standardised testing and frameworks that capture reliability, inspection and interacting failure modes.