Comment Re:7.5 ton UAV testing flight (Score 4, Informative) 63
intercalation (a saturated solution of hydrogen in a charcoal-like solid).
Neither liquid nor compressed gas can match intercalation for volumetric efficiency.
It's safer than compressed, as well as lower-storage-cost than refrigerated liquid.
Compressed gas is a no-no for flight safety
reasons: you can't depend on soft landings.