I guess I'm asking the wrong question. Let me rephrase with another example.
Assume I have a bottle of liquid hydrogen. It's connected to a non-porous balloon with no elasticity made of, say mylar. The maximum volume of that balloon is 1,000 cubic meters. I open the valve on my hydrogen and the balloon begins to fill. Assuming the balloon never breaks, for every liter of liquid hydrogen I let escape, what is the pressure inside that balloon? How does that pressure change based on temperature? And assuming the maximum volume of that balloon won't increase or decrease, based on altitude will the internal pressure change (I assume it won't)?
Please, I need a simplified mathematical formula I can plug into game code that gives me this pressure. This formula will represent the filling of gas bags in a rigid airship and I basically need to know when to make them rupture based on over/under inflation.
I know this has to do with the ideal gas law. But, for the past 2 days I've been researching and trying to get a working formula with no success.