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PRISM: Passive Ramjet Inertial Stabilization Mechanism Open Access

Passive Ramjet Inertial Stabilization Mechanism, henceforth referred to as PRISM, is an aerodynamically driven gyroscope which aims to counter the natural pitching and yawing moments of a sounding rocket. The concept was originally developed for the Intercollegiate Rocket Engineering Competition, and strict requirements had to be met in order for PRISM to be accepted. PRISM must: integrate into a standard six inch diameter rocket, be a passive system (i.e. not able to be controlled after launch), limit the pitch and yaw of a rocket to within ten degrees, not add significant drag to a standard rocket, and must withstand the physical forces of launch and landing. Based on these requirements, the following design was conceived. It is made up of a forward hardpoint to direct the airflow through the nose cone to outlet holes, a turbine fan blade mounted on a steel shaft assembly, and an electronics bay located in a standard six inch rocket coupler. During flight, airflow is naturally forced through the hollow nose cone, the turbine blade extracts energy from that airflow, and the turbine blade-shaft assembly spins as a result. The spinning shaft provides the torque, or rotational force, to counter the pitch/yaw of a rocket through a phenomenon known as gyroscopic precession. A spin test was conducted to determine if the turbine blade would spin up using a compressed air line shot directly against the blade, and the shaft successfully spun up to about 3,000 revolutions per minute. A flight test was conducted with PRISM mounted on a standard six inch rocket; the rocket flew at about 305 miles per hour and PRISM spun up to 8,000 revolutions per minute, and the preliminary data shows that the rocket hovered at zero degrees in both the pitch and yaw directions. The results are promising for this pioneering system.

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