I wasn't saying there's no alternatives; indeed current ICBMs use very little helium. It's not just about pressurizing the liquid fuels for main engines. It's

I wasn't saying there's no alternatives; indeed current ICBMs use very little helium. It's not just about pressurizing the liquid fuels for main engines. It's a purging gas; it can be used to pressurize RCS systems where other approaches are less practical; etc etc etc.