Author(s): Capt. Donald C. DePreesm
Published in: NAVIGATION, Journal of the Institute of Navigation, Volume 17, Number 2
Pages: 190 - 199
Cite this article: DePreesm, Capt. Donald C., "THERMAL PRECONDITIONING UTILIZING A RADIOISOTOPE HEAT SOURCE", NAVIGATION, Journal of The Institute of Navigation, Vol. 17, No. 2, Summer 1970, pp. 190-199.
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Abstract: Gyroscopes and accelerometers used as sensors in inertial navigation systems have errors which change with temperature. In order to obtain adequate performance from these devices; precise, elevated (above ambient) temperatures are usually required to aid in maintaining close tolerances of temperature control. Most systems include electrical heaters on these sensors for this purpose. The time required for the sensors to reach operating temperature has been excessive, especially if the ambient temperature is low. Thermal preconditioning eliminates the warm-up time by maintaining the entire inertial measurement unit (IMU) near the operating temperature of the sensors. This technique has not been practical in the past because continuous electrical power could not be provided and sources of portable power were not adequate to supply the heating requirements of large inertial systems. The size of inertial systems has been decreasing and the small systems can be kept near operating temperatures with less than 65 watts of thermal power even at low temperatures. A joint AFC/Air Force program to test the feasibility of using radioisotopes as heat sources to keep the inertial measurement unit at or near operating temperature was conducted. This paper discusses the design, operation and test of the thermal preconditioning unit utilizing a radioisotope heat source. Thermal and radiological safety aspects are also included in the discussion.