Cryogenic Thermal Design of Electromagnetic Formation Flight Satellites
- Paper number
IAC-08.C4.3.3
- Author
Mr. Daniel Kwon, Massachussets Institute of Technology (MIT), United States
- Coauthor
Prof. Raymond Sedwick, University of Maryland, United States
- Year
2008
- Abstract
An emerging method of propellant-less formation flight propulsion is the use of electromagnets coupled with reaction wheels. This technique is called Electromagnetic Formation Flight (EMFF). In order to create a large magnetic moment necessary for actuating formation flying spacecraft, EMFF uses high temperature superconducting (HTS) wire since it is able to hold a large current. To achieve superconductivity, the HTS needs a cryogenic thermal control system to maintain the wire temperature below the critical temperature and this temperature must be maintained over the entire EMFF coil, which could be as large as two meters in diameter. For commercially available HTS wire, this critical temperature is 110 K. Since EMFF obviates the need for consumables for formation flying maneuvers, the thermal system must also be consumable-free. This paper investigates a consumable-free method of maintaining isothermalization for a large scale HTS coil. The HTS coil resides inside a thermally conductive jacket which is used for isothermalization. A cryocooler is attached to the thermally conductive jacket and is used for heat extraction. Wrapped around the thermally conductive jacket is multilayer insulation which is used to reduce the heat load into the HTS coil. This thermal system has the flexibility for a rapidly changing thermal environment, such as low Earth orbit. Both a solid conductor and a heat pipe were investigated for use as the thermally conductive jacket. Analytic and finite difference models were developed to model a single coil in space and a coil inside a vacuum chamber. In addition, this paper investigates the design, operation, and testing of a cryogenic heat pipe. The heat pipe uses nitrogen as a working fluid and a stainless steel mesh as the wicking structure. As a proof of concept, a 90 cm heat pipe was constructed as the thermally conductive jacket enclosing the HTS wire. The working fluid, at saturation temperatures, maintains a constant temperature below the critical temperature. Testing of the heat pipe in a vacuum chamber was conducted to verify the power capacity of the heat pipe. Verifying the proof of concept cryogenic heat pipe has lead to construction of a full scale heat pipe integrated with HTS wire for testing in a six feet diameter toroidal vacuum chamber. The results of this test will demonstrate the feasibility of operating large HTS coils for future formation flying missions.
- Abstract document
- Manuscript document
IAC-08.C4.3.3.pdf (🔒 authorized access only).
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