Design and fabrication of a thrust stand for a 30-kw class plasma arcjet engine
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Thermal arcjet thrusters because of their high specific impulse ranging from 1000 to 2000 seconds are promising candidates for primary propulsion applications in many of the ambitious space projects currently under consideration. Thermal arcjet research began in the late 1950s, and continued until the mid 1960s. In 1960s, the AVCO engineers and scientists, who carried out most of the initial work in the development of the thermal arcjet thrusters, designed a pendulum type thrust stand to use in their 30 kW arcjet development program. Work on arcjet engines stopped during the late 1960s, because development work on suitable power sources had ceased. In the 1980s, when thermal arcjet research was restarted in this country, JPL and others used the AVCO thruster design while they used their own thrust stand designs to repeat A VCO performance. The thrust decay over time after the power supply is turned off was rapid for these thrust stand designs compared to A VCO results. The two factors contributed to the time involved in the thrust decay are the response time of the thrust stand and the thrust produced by the heat input to the propellent gas from the hot arcjet engine walls. The objectives of this research were to design and fabricate a repetitive and reliable thrust stand similar to the A VCO design and to determine the response time of the thrust stand by conducting cold flow tests. A detailed description of the thrust stand design, design of the subsonic nozzle used for the cold flow test, calibration of the thrust stand under different conditions and the cold flow tests are given in the following chapters. Different calibrations proved the repetitiveness and the reliability of the thrust stand. The response time of the thrust stand was found to be close to 2.4 seconds while opening and 3 seconds while closing.