An experimental investigation of the jet damping effects of a solid rocket motor

The purpose of this experiment was to investigate the interaction between the combustion gases of laboratory scale (2.0 inch diameter) solid rocket motors and the rocket motor dynamics. Under normal conditions, this interaction leads to a decrease of a vehicle's lateral angular velocity. This is known as jet damping. But in larger, spin stabilized solid rocket motors, such as the STAR 48 family of motors, the lateral oscillations grow during the motor burn. This phenomenon is known as "coning" or "nutation" of the spacecraft. An experimental apparatus was designed and built to measure the magnitude and direction of the side force generated in small rocket motors. This test stand spins the rocket motor about two axes. One electric motor spins the rocket motor about its longitudinal axis, which simulates the spin of spin stabilized vehicles. The other electric motor spins the rocket about a transverse axis. Strain gages mounted on flexures measure the side force produced by the rocket motor during the motor burn. Both aluminized and nonaluminized rocket motors are utilized to investigate the effects of the accumulation of aluminum oxide slag in the combustion chamber. To date only one rocket motor has been fired, resulting in some damage to the hardware as a result of an O-ring failure. Testing is expected to continue when new parts are made. This test stand promises to provide useful results in the investigation of jet damping and jet driving phenomenon.