Tangentially related. I worked on a space opera setting where the hydrogen economy was a big thing. Gravity and mass were still issues for space travel although there were some FTL and alien tech. In any case, the Sol system gas giants were being mined for Helium-3 fusion fuel. Helium-4 is the inert gas we commonly thing about when we say helium. Due to mass concerns, space ships would often use helium as a buffer gas instead of nitrogen. And the dive ships which would enter the atmosphere of Uranus had multiple pressure hulls, plus hardsuits for the crew. Even then, they would use a heliox mixture for the dives. These were some of the bravest and baddest ass mutha fraggers in the solar system and they all sounded like mickey mouse because of the helium.
