Performance measurements on a pulsed ablating thruster.

Abstract

A new type of pulsed thruster is described, and measurements of the momentum communicated to a pendulum by the gas blast are reported. With the use of a honeycomb collector on the pendulum, the error introduced by reflecting particles was eliminated. At a maximum total electrical discharge energy of 2800 joules, of which approximately 1700 joules were dissipated in the thruster, a momentum of 8150 g-cm/sec was measured. Measurements of mass consumption per shot yielded values ranging from 2-8 mg shot, depending on operation. Momentum and mass consumption measurements point to effective specific impulse values of approximately 1000 sec. Direct measurement of exit velocities using high-speed photography yielded effective specific impulses close to 2000 sec. The two measurements are compatible with each other because the photographic measurements are expected to yield data that are too high. Measured efficiency for conversion of electrical energy dissipated in the thruster into directed thrust-producing flow was determined to be 20%.