[Ford4000]

Anyone know why they use helium rather than some easier-to-contain gas?

[bankwalker]

it is inert ...

[know.your.why]

Fun at parties?

[The Louiswu]

"Anyone know why they use helium rather than some easier-to-contain gas?"

My understanding is that Helium has been used since Apollo to pressurize the fuel tanks. Helium does not mix with the fuel used as propellant and it forces the rest of the fuel into the fuel lines.

Early Apollo flights, before the introduction of Helium encountered a pogo effect as the fuel would "bounce" and swish inside the tanks since there was "nothing to hold it down", pressurized Helium solved that issue and they have been using it every since.

I just read this in a book about the Apollo 8 mission.