One of the main elements of NASA’s Space Launch System (SLS) Core Stage that makes it more than just a big fuel ... large valves that control the flow of liquid oxygen and liquid hydrogen ...

Mr Bruno said the issue occurred in a valve which controls fuel pressure ... oxygen and hydrogen from the Atlas V first and second stages was also removed to ensure the rocket's safety.

Silent Depths: How Hydrogen Valves Power Modern Submarines** Submarines ... systems use hydrogen fuel cells to generate electricity, ensuring near-silent operation when submerged.