Supersonic Rockets' Stability

[John Feller]

Hello all,

I am trying to design a supersonic rocket on Open Rocket program with N2900 motor. I wonder that how I can keep the stability between 1,5 and 3 during flight, since the propellant weight is really high and critically effects the center of mass of the rocket to the forward during the flight.

Thanks in advance!

 

[ether]

OR can plot the CP, CG and stability margin as the flight progress. RasAero (https://www.rasaero.com/) is great software for mach flights, provides same information (CP, CG and stability margin through the flight)

 

[OverTheTop]

If you keep your rocket relatively short, with some of the motor mass forward of the CG you can reduce variation during flight. That way you lose mass both forward and aft of the CG during burn. You need to get creative with recovery systems

I guess the other method would be to build a rocket heavy enough so that the mass change of the motor is not as significant.

I am guessing there will be a CP shift forward with a motor like that pushing the speed past supersonic. You need to make sure your sims take that into account also. Most do, and you can chart stability margin during the simulated flights.

 

[diyaerospace]

I recently had a 24mm mach 1 rocket flip out of control as it approached mach. Others on the forum suggested that that stability margin of 1.73 on that flight was to low. I have made changes to the design but have not yet tried them out. Based on my limited experience and suggestions from others a margin of at least 2.25 is good for mach 1 flights. But I don't know much about of your design and based on the motors your using it is probably much bigger than mine, so my previous words might not apply to your rocket