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Testing Fundamental Properties of Ionic Liquids for Colloid Microthruster ApplicationsNASA's New Millennium Program is scheduled to test a Disturbance Reduction System (DRS) on Space Technology 7 (ST7) as part of the European Space Agency's (ESA's) LISA Pathfinder Mission in late 2009. Colloid Micronewton Thrusters (CMNTs) will be used to counteract forces, mainly solar photon pressure, that could disturb gravitational reference sensors as part of the DRS. The micronewton thrusters use an ionic liquid, a room temperature molten salt, as propellant. The ionic liquid has a number of unusual properties that have a direct impact on thruster design. One of the most important issues is bubble formation before and during operation, especially during rapid pressure transitions from atmospheric to vacuum conditions. Bubbles have been observed in the feed system causing variations in propellant flow rate that can adversely affect thruster control. Bubbles in the feed system can also increase the likelihood that propellant will spray onto surfaces that can eventually lead to shorting high voltage electrodes. Two approaches, reducing the probability of bubble formation and removing bubbles with a new bubble eliminator device in the flow system, were investigated at Busek Co., Inc. and the Jet Propulsion Laboratory (JPL) to determine the effectiveness of both approaches. Results show that bubble formation is mainly caused by operation at low pressure and volatile contaminants in the propellant coming out of solution. A specification for the maximum tolerable level of contamination has been developed, and procedures for providing system cleanliness have been tested and implemented. The bubble eliminator device has also been tested successfully and has been implemented in recent thruster designs at Busek. This paper focuses on the propellant testing work at JPL, including testing of a breadboard level bubble eliminator device.
Document ID
20070023747
Acquisition Source
Jet Propulsion Laboratory
Document Type
Preprint (Draft being sent to journal)
External Source(s)
Authors
Anderson, John R.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Plett, Gary
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Anderson, Mark
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Ziemer, John
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Date Acquired
August 23, 2013
Publication Date
July 9, 2006
Subject Category
Fluid Mechanics And Thermodynamics
Meeting Information
Meeting: 42nd AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit
Location: Sacramento, CA
Country: United States
Start Date: July 9, 2006
End Date: July 12, 2006
Distribution Limits
Public
Copyright
Other
Keywords
bubble formation
propellant
micropropulsion
cleaning methods
bubble eliminartor

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