Super Soaker Central

During my thermodynamics class we had a discussion about modeling a system based on a balloon. As a curiosity I Google "pressure of a balloon" to see what would come up. Check it out: http://www.vernier.com/caliper/spring02/balloon.html

The graph is similar to what I saw when testing the pressure of LRT. The pressure spikes at the beginning and then increases slowly. With LRT the spike was larger and the increase was slower, but the basic trend was the same.

Neat link and interesting findings. I wonder, though, what the pressure curve ends up looking like for Super Soaker CPS chambers since the walls are tapered to some degree.

The pressure curve would definitely be very similar. I'd imagine with a taper the slope of the linear part would be lower but that's just a guess. A smaller ID with a constant wall thickness has higher pressure compared against a larger ID with the same wall thickness.

That's really neat. I wonder what would happen if they didn't fill the balloons to bursting, and just refilled them. You probably wouldn't see the initial spike anymore.

The initial spike existed in all tests I did with latex tubing so I'd imagine it'd remain if they didn't pop the balloons. The initial spike seemed to end once the tubing started expanding so my guess is that it takes a certain pressure level to expand the tubing but the pressure drops after that.

I wonder if the taper is to suppress that spike?

@cantab: I believe, as Ben said, the initial pressure spike would remain. The taper likely serves a different function; perhaps keeping pressure more constant after the initial expansion point is reached or minimizing potential wall-friction as the chamber deflates/pushes out water through the nozzle.