We are just going to disagree on that. Remember, a gas is contained by a pressure vessel, not a tank. Pressure vessels are much thicker. As a result, they are more robust and less prone to impacts of flight dynamics. Metal fatigue is tested for periodically, just like structural integrity metal fatigue of the plane.

I'm looking at four welding tanks that are across the room from me. Pressure Vessel vs tank is semantics.

There are very light pressure vessels, and tanks that will hold insane pressure.

Liquid Hydrogen is kept liquid by keeping it COLD, How cold? Keeping it cold is easier/lighter than keeping it compressed to a pressure where it will have similar energy density. It is practically impossible to compress hydrogen to the density of liquid hydrogen in large quantities in anything light enough to fly. Hence why LH2 is the preffered way to fuel rockets.

Liquid Hydrogen boils at sea level pressure at 20K That's 20 degrees above absolute zero. -423F if you want to put it into Fahrenheit units.
If you aren't going to be using it faster than it boils off, you do need a way to vent it.

What do I know, I just worked with cryogenics for years. Have a fancy degree with letters after my name and before it if that matters.

I would suspect that the more likely source of leaks would be the plumbing not the tanks. But assuming we are talking about liquid H2 it actually doesn't have to be a pressure vessel at all, it could just be a tank that's vented for boil-off pressure relief.

Space launch vehicles tend to use pressure vessels because the pressurized tank is an integral structural component of the rocket. They also use near paper-thin walls, and it only needs to work once (for traditional expendable boosters).


For clarity I've been talking about liquid H2, pressurized gaseous H2 I don't think is practical for large airplanes...

Too little pressure and you can't carry enough. Too much pressure, and the weight of tank becomes impractical. And those points would overlap.

Pressure Vessels vs. Tanks. A lot of lay people say the difference between a jet engine and a piston engine is just semantics. You and I know that is incorrect. Just like gassing up a jet plane is not correct.

Pressure Vessels are most often designed to ASME VIII. They are designed, tested, and stamped for a Maximum Allowable Working Pressure, generally above 15 psig.

Tanks are designed to hold the static head of the liquid and a few inches of water column pressure (a fraction of a psig). They are entirely different design codes.

Big difference. Again, the lay person intersperses words that they think are fine, but are clearly incorrect.

Liquid Hydrogen or Gaseous Hydrogen still has the same size H2. They leak through exactly the same size holes.

Liquid Hydrogen boil off is like LNG boil off. Liquified Natural Gas (LNG) is dropped to -260F in its liquifaction process plants, on shore. It is then moved by ship, long distances. The ships use LNG as boiler fuel. Nothing keeps it cold, other than insulation, once it is in the storage vessels of the ship. As it boils off, the gaseous natural gas is used or is vented. There is nothing to reliquify it, once on board. When more is needed for boiler fuel, they have heat exchangers to use sea water to vaporize the LNG.