Significant Increase in the Cryogenic Pumping System Capacity and Reliability for the CHAFF-IV Plume and Contamination Facility

摘要

The interactions between exhaust plumes and the ambient, high altitude atmosphere have been investigated by the components of the Department of Defense for many years. To date, laboratory investigations of space plumes from firing thrusters and simulated ambient environments have been difficult to achieve due to limitations in pumping speed. The major limitation of ground- based facilities in accurately predicting the effects of thruster operation on spacecraft systems has always been driven by the facility's background pressure. The Chamber-IV of the David P. Weaver Collaborative High Altitude Flow Facility (CHAFF-IV) at the University of Southern California is used for such investigations. One of the critical components of the CHAFF-IV pumping system is a cryogenic helium refrigerator (or cryostat) that supplies gaseous helium at 15 - 20 K to the pumping panels. Higher speed CHAFF-IV pumping for both chemical and electric thrusters allows accurate thruster interaction studies to be performed through the addition of a high capacity commercially available cryostat. Significant increases (approximately a factor of 5) in the pumping speed allows for higher power thrusters (on the order of 10 - 15 kW) to be operated in the facility. This addition satisfies recent interest in very high power electric ion thrusters and also high flow rate chemical engines operating on advanced (higher temperature) propellants. Additionally, it allows for multiple small thrusters to be fired simultaneously to simulate microspacecraft platoon or constellation formation and operations.