Torsional thrust balance measurement system development for testing reaction control thrusters

The paper describes the design, development, and testing of a torsional-type thrust stand to evaluate the performance of <40 N class cryogenic propellant reaction control thrusters. New thrust measurement techniques for cryogenic propellant fed reaction control systems at this thrust class are needed as current methods are deficient in providing reliable test data. The torsional thrust stand primarily consists of a balanced moment arm rotating around a set of frictionless pivots. The displacement of the moment arm due to applied thrust was tracked using a laser displacement sensor. A post-processing technique was developed to determine thrust values from displacement data. The measurement capability of the thrust measurement system is exemplified herein through the test firing a LOX/Methane thruster at steady-state and pulsing conditions. Effects of thruster mass and feed system stiffness on thrust-stand measurement characteristics were also assessed. The measurement system provided repeatable thrust data at steady-state and pulsing operating conditions.