What are those things that detach from the shuttle at the last minute?

Originally Posted by Me

On Jul 5, 7:07*am, peanutaxis
wrote:
They look like hoses or something. I mean I can understand that things
need to be attached, but do they really need to be attached until the
split second the rocket takes off?

--
peanutaxis

Yes, they do
They carry propellants. If the shuttle were to delay or scrub, they
used to replenish or drain the propellants. Dangerous hydrogen gas is
being vented off and that needs to be attached for the same reasons.

Some hoses carry conditioned air/nitrogen, others carry data and power.

Why is there hydrogen gas around. I thought it'd be all liquid and all contained!