Development of a Rocket Motor Burn Rate Measurement System

The technique chosen to develop into a microwave burn rate sensor was that of the microwave interferometer. Microwave engery is beamed through a 'window' in the rocket motor case and into the propellant. At the burning propellant surface, this microwave energy is reflected and beamed back through the 'window' to a detector system. At this detector system, the combination of transmitted and reflected energy produces a standing wave of energy which is monitored by the detectors. As the burning surface moves, the standing wave will also move a proportional amount. Thus, by monitoring the motion of the standing wave, the motion of the burning surface is obtained. (Author)