Local thermal management for space-borne inflatable RF antennas

Abstract

With the space shuttle payload cost at approximately $10 K per pound, emphasis is being placed on reducing the weight of space-based systems. NASA is presently developing lightweight RF components such as inflatable antennas. We have investigated one key issue of the inflatable antenna: thermal management of the RF electronics. Our approach, called local thermal management (LTM), is a technique of heat removal based on the dual use of the RF ground-plane layer of the antenna, which consists of a copper film with Kapton cladding on one side and an emissive IR material on the other. The copper reflects the RF antenna pattern and also spreads and transfers the heat to the IR emissive layer. Our LTM concept was investigated for a radar application at 1.25 GHz (L band) in which the dissipated power of the RF electronics is 1.2 W. Experiments were conducted in vacuum (3 /spl times/ 10/sup -6/ torr) on a unit cell of the antenna where a resistor was bonded and biased for 2 W heat dissipation. The experimental data was then used to calibrate an Icepak/spl trade/ 4.0 numerical simulation of an inflatable antenna cell in the low earth orbit (LEO) environment, taking into account the thermal fluxes from the earth and sun. The simulation predicted a junction temperature of 122/spl deg/C well within the range of safe electronics operation.