Joey:
Some inputs:
1) Others can confirm, for supersonic rockets my RASAero II software is more accurate than RockSim. For a "yolo" or "bragging rights" flight, if you are not taking any in-flight data, you should run the rocket on the most accurate software, because that is the Mach number which you are going to claim for your rocket. RASAero II is free, and it can import RockSim files, but since more details on the rocket have to be inputted you'll have to spend a little time converting your rocket file.
2) I'd really encourage you to put at least a simple barometric altimeter on the rocket. Others here can recommend some units, but they are quite small and would not really decrease the performance of your rocket by much. From this you would get the apogee altitude of the rocket. Why is that useful? If your RASAero II predicted apogee altitude is very close to the barometric altimeter apogee altitude, then you can be reasonably confident that the RASAero II predicted maximum Mach number is probably very close also. Just this one piece of additional information will tell you a lot about how the flight went. Without it, you just shot a rocket off, and then exclaim "it went Mach 2!".
3) I would not use the velocity from the barometric altimeter, because it is not hooked up to a calibrated pitot (air data) system. But it will take accurate altitude data through apogee, as the rocket is flying at very low velocity through apogee. (As a note, combining an accelerometer with a barometric altimeter is a powerful combination, the accelerometer provides the best data during boost and early in the coast, the barometric altimeter provides the best data through apogee.) Many of these small barometric altimeters just record the apogee altitude, and then they beep it out when you recover the rocket via a series of beeps. Again, they are small, they will have little impact on the performance of your rocket. But you will have to get your rocket back, the data is stored on-board the rocket, not telemetered to the ground. Thus, see item 4).
4) Since you have to get the rocket back to get your flight data, depending on what kind of field you fly from (grass or a dry lakebed), for this type of small rocket you likely want to put a beeper in the rocket (others can recommend units) that lets out a shrill beeping sound to help you figure out where the rocket has landed. Your rocket will be flying high and fast, and since you have made it as small as possible to maximize performance, you are likely going to have a hard time finding the rocket.
By the way, this is very doable. For STEM classes I've thought of similar just over supersonic rockets using smaller motors using similar instrumentation.
Charles E. (Chuck) Rogers
Rogers Aeroscience