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Feasibility Study of Jupiter Icy Moons Orbiter Permanent Magnet Alternator Start SequenceThe Jupiter Icy Moons Orbiter (JIMO) mission was a proposed, (recently cancelled) long duration science mission to study three moons of Jupiter: Callisto, Ganymede, and Europa. One design of the JIMO spacecraft used a nuclear heat source in conjunction with a Brayton rotating machine to generate electrical power for the electric thrusters and the spacecraft bus. The basic operation of the closed cycle Brayton system was as follows. The working fluid, a heliumxenon gas mixture, first entered a compressor, then went through a recuperator and hot-side heat exchanger, then expanded across a turbine that drove an alternator, then entered the cold-side of the recuperator and heat exchanger and finally returned to the compressor. The spacecraft was to be launched with the Brayton system off-line and the nuclear reactor shut down. Once the system was started, the helium-xenon gas would be circulated into the heat exchangers as the nuclear reactors were activated. Initially, the alternator unit would operate as a motor so as to drive the turbine and compressor to get the cycle started. This report investigated the feasibility of the start up sequence of a permanent magnet (PM) machine, similar in operation to the alternator unit, without any position or speed feedback sensors ("sensorless") and with a variable load torque. It is found that the permanent magnet machine can start with sensorless control and a load torque of up to 30 percent of the rated value.
Document ID
Document Type
Technical Memorandum (TM)
Kenny, Barbara H.
(NASA Glenn Research Center Cleveland, OH, United States)
Tokars, Roger P.
(Purdue Univ. West Lafayette, IN, United States)
Date Acquired
September 7, 2013
Publication Date
February 1, 2006
Subject Category
Spacecraft Propulsion And Power
Report/Patent Number
Funding Number(s)
WBS: WBS 22-982-10-50
Distribution Limits
Work of the US Gov. Public Use Permitted.
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