Calculating...

I've written a very simple simulator to try and do some vehicle optimizations.
Using a very simple drag model... I used the data from page 16 of
http://www.jmrconline.org/Drag_Coefficient_Prediction.pdf built a table of mach number and Cd and interpolated. (This is actual data from a 5" rocket, were building a 6" rocket so it seems reasonable)


One of the interesting results is this graph:

It shows peak altitude achieved (y axis in meters) piloted against the equivalent peak drag. The peak drag units here are equivalent velocity at sea level in m/sec. The peak is at 50500m and 303m/sec (165Kft and 677mph)

Another interesting result (from a slightly different run) I'm not using any real fancy integrator and the results vs time steps don't change much:

Time Step	Alt
1	47458
.1	49532
.01	49576
.001	49593

So this means for very crude integration steps you get reasonable results, thus allowing one to use the model for optimization seeking. Right now there are a number of limitations, the model assumes that the ISP does not change as the motor is throttled for peak drag limiting etc... so as I add more detail to the model it will be interesting to see what happens.