I have now completed a basic 0-D two stage LGG simulation to get an idea of design parameters (for those not familiar, 0-D codes do not account for the mass of the gas, resulting in the pressure of one large body of gas being uniform anywhere inside that body at a given time). This code works similarly to GGDT, except it doesn't have a GUI, and doesn't do this:
There's so much more to learn with the inclusion of double-staging. I'm having to develop a whole new intuition for gun behaviour, and there's so much more to consider that it can easily take an hour to roughly optimize a single design for a given projectile mass and diameter.
What I was trying to determine here was just how much higher the driver gas pressure could exceed the diaphragm's rupture pressure (you just can't do an 80kpsi burst disk - it's too thick). That was a success - using a 100MPa diaphragm, I can easily get the model to produce average
propelling pressures of three times that (and maximum pressures over fifteen times that, if I'm not careful...).
I'm a bit short for time here and will update later, but the next step is to develop a proper 1-D code to refine the process, and possibly a 2-D CBA code for the driver gas side (more on that later).
Spudfiles' resident expert on all things that sail through the air at improbable speeds, trailing an incandescent wake of ionized air, dissociated polymers and metal oxides.