There is a lot if information on the net about the physics. Here is one link.
http://web.mit.edu/womens-ult/www/sm...ee_physics.pdf
But it is probably more useful to obtain empirical data on your particular launcher design than working from these equations. I think the science give you a good idea of what to expect, and how to influence the result. But might be difficult to use to evaluate a design without initial test data.