Liquid Hydrogen

Basics

• The liquid state of hydrogen
• Useful as a fuel storage method, and as a Cryogen
• Often Abbreviated as LH2
• According to wikipedia "To exist as a liquid, H2 must be cooled below its critical point of 33 K. However, for it to be in a fully liquid state without boiling at atmospheric pressure, H2 needs to be cooled to 20.28 K[3] (−423.17 °F; −252.87 °C)."
• A Common Rocket Fuel (Usually with LOX )
• Neutron Scattering Supposedly Uses LH2
• LH2 is also used for particle physics with Bubble Chambers although they have largely been replacecdd by other technologies

Advantages

• Density of storage

Disadvantages

• It's a Cryogenic Liquid (thus can burn people), and requires intense cooling
• Cryogenic Liquid Boil-Off caused losses, or required active cooling
• Asyphxiation Hazard (although not as bad as heavier gasses, in large enough volumes, it can displace oxygen, thus ventillation and/or sensors are needed
• As with any hydrogen, a pure flame is invisible in the visible spectrum, and thus may be harder to detect
• As spacex's starship tests have shown, poorly welded/constructed tanks have a nasty habit of bursting and/or exploding

Useful Links

• The Wikipedia Page on Liquid Hydrogen
• Archival Footage of 1960's Testing on Liquid Hydrogen Storage Hazards by the USA Air Force (shows leaks, and fires, and compares them to similar JP-4, and gasoline etc events) (Didn't detonate in small leaks (1+1/4 gal), only a slow flame (still a flame, but not an explosion) ,similar for 32 gallon (albeit more flame), All in all, without pre-mixing detonation does not happen, in premixed, little to no overpressure was observed, but the thermal radiation may start fires
  • All in all less bad than an ignition event of liquid hydrocarbons (If not mixed with air/oxygen, if ignighted NOT by an explosive, etc), but is easier to ignite
  • Granted this is OLD, and the main measurements were with film? NEEDS MORE RESEARCh