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Microsystems in Spacecraft Thermal Control 201
low heat capacity, and low thermal conductivity heat transport paths, they can
exceed their survival temperatures very easily in a short time.
MEMS thermal control devices need to be properly protected for physical
damages. Sensors and actuators coming into contact with the environment
must be protected against adverse affects, especially if the devices are subject to
long-term reliability concerns. Careful procedures need to be considered during
design and handling of MEMS TCS to prevent potential threat of humidity,
contamination, and charging. Ground handling is as much of a concern as in-
space operations.
Similar to other components on a spacecraft, MEMS thermal control devices
are susceptible to space environment induced damages. Therefore, ground-based
environmental tests must be conducted on the final flight design to verify surviv-
ability of MEMS thermal control devices. Based on mission conditions, a list of
environmental test requirements will typically be established for the MEMS de-
vices.
9.5 CONCLUSION
Spacecraft TCS use both passive and active thermal control devices to maintain
spacecraft systems within allowable temperature ranges. Passive thermal control is
the most commonly used, while active thermal control is employed to accommodate
stringent temperature control requirements, high power dissipation, and to provide
design flexibility. Passive thermal control devices do not contain either moving
parts or fluids. Based on these distinct characteristics, MEMS TCS are categorized
as mainly an active thermal control concept.
Future space missions require complex spacecraft design, operation scenarios,
and flight configurations. The push for low-cost and short-assembly schedules
increases the demand for nano- or microsatellites. MEMS thermal control devices
may become a critical element in such applications as they offer some unique
advantages, especially for small spacecraft. Although the development of MEMS-
based technology is still in its infancy, the advancement in MEMS thermal control
devices is moving forward.
REFERENCES
1. Birur, G., G. Siebes, and T.D. Swanson, Spacecraft thermal control, in Encyclopedia of
Physical Science and Technology. 2002.
2. Incropera, F.P. and D.P. DeWitt, Introduction to Heat Transfer. Third ed. 1996, John
Wiley and Sons, Inc., New York, NY.
3. Wingate, C.A., Spacecraft thermal control, in Fundamentals of Space Systems, Pisacane,
V.L. and R.D. Moore, Editors, 1994, Oxford University Press, New York, NY, p. 443.
4. Biter, W., S. Oh, and S. Hess, Electrostatic switched radiator for space based thermal
control, in Space Technology and Applications International Forum — STAIF 2002.
2002, Albuquerque, NM.
© 2006 by Taylor & Francis Group, LLC