How can I calculate the propulsive force produced by ejection of a gas? I suppose it depends on the gas, the velocity with which it ejects, the amount of gas, and some other parameters, like the geometry of the nozzle for example. I would like a calculator to play with the gas density, the gas velocity etc, and see the various propulsive forces generated.
It's pretty basic conservation of momentum kind of problem. A converging diverging nozzle is used to accelerate the gas such that it's supersonic leaving the nozzle. These problems are pretty well-defined. There are lots of calculators out there that let you monkey around with varying different parameters without getting into a full on mathematical understanding of compressible flow. Here's one: