Proportional Flow Control Valve (PFCV) for Electric Propulsion Systems

State of the art flight xenon feed systems typically operate using a two stage architecture: a pressure control system and a flow control system. The pressure control section typically contains a pressure regulator, either mechanical or electronic, while the flow control section usually contains either a thermal throttle or a fixed orifice. As electric propulsion technology matures and becomes a larger part of the standard spacecraft propulsion system, active flow rate control to the engine will become standard. This active flow control wiil replace the two separate systems flying today with a single flow control element. The resulting system will be smaller and lighter while directly controlling the key parameter for engine operation: xenon flow. This paper describes the development effort that has been completed by Moog to design a Proportional Flow Control Valve (PFCV) that has extensive flight heritage to other Moog Electric Propulsion (EP) components. Background design information as well as development test results conducted at Moog are presented. Introduction The Moog PFCV, shown in Figure 1, is a proportional electro-mechanical valve that has demonstrated excellent control capability over a large range of xenon inlet pressures. Development tests have demonstrated controllable flow rates from 0.2 seem to more than 300 seem over the full range of inlet pressures from 3200 psia to less than 1 psia for the lower flow rates. One of the primary design considerations for the PFCV is the use of extensive flight heritage designs. Therefore the PFCV has design heritage from the Moog 1 Engineering Section Head, AIAA Member 2 Staff Design Engineer Copyright © 2000 The American Institute of Aeronautics and Astronautics Inc. All rights reserved solenoid valves that were used on Jet Propulsion Lab's (JPL) Deep Space One (DS1), Moog Module M Xenon Feed System and various mono-propellant and bipropellant applications. A summary of the qualification history for these Electric Propulsion solenoid valves is shown in Table 1. Valves of the PFCV family have the following critical characteristics: • Common parts to allow for larger manufacturing and assembly runs. This reduces the overall cost of the valve. • No sliding fits. Moog utilizes a suspended armature design which incorporates Moog standard S-Spring technology. This is critical for EP feed systems since contamination control is a driving design requirement. • Vespel® seal which is used to provide isolation as well as flow metering. Vespel is utilized in EP systems due to its dimensional stability as well as its lower outgassing properties. Again, the selection of Vespel® is driven by the contamination sensitivity of the EP feed system. • Common interface for direct integration with standard Moog EP solenoid valves, Moog Models 51E190 and 51E186. This facilitates integration to the top level assembly. • All welded configuration. • 0.125 inch inlet and outlet tube configured for orbital tube welding into standard EP systems. Figure 1, Moog PFCV, Model 51X198 1 American Institute of Aeronautics and Astronautics (c)2000 American Institute of Aeronautics & Astronautics or Published with Permission of Author(s) and/or Author(s)' Sponsoring Organization.