Liquid hydrogen tanks are definitely a different problem, but I don't know if "orders of magnitude safer" is necessarily true. Many spacecraft have run into pro

Liquid hydrogen tanks are definitely a different problem, but I don't know if "orders of magnitude safer" is necessarily true. Many spacecraft have run into problems involving liquid hydrogen storage for a variety of reasons: - Liquid hydrogen is so cold that many metals weaken - Exposure to hydrogen itself weakens many metals (hydrogen embrittlement) - Liquid hydrogen expands rapidly if exposed to heat, so venting is needed - Hydrogen leaks through the smallest of seams Now imagine trying to build a tank that prevents all that from happening, and it has to be lightweight for usage on spacecraft / aircraft.