Hybrid LHP/Composite Heat Rejection Panels for UAV

Ongoing work should lead to a flight test of a Loop Heat Pipe based anti icing system in late 1998 or early 1999 aboard the Global Hawk UAV. The Loop Heat Pipe condenser tubing will be integrated into the composite skin of the engine inlet cowl. This essentially turns the composite skin into a radiator panel. The proposed program will address and quantify the use of these panels as heat rejection radiators. Such radiator panels can be applied to most of the upper surface of the aircraft and are equally suited for convective or radiative heat rejection. The concept supports a self-contained by-pass system which will autonomously switch in additional panels as the system temperature rises in response to diminished convective heat loss with altitude so the system will passively maintain operating temperature limits. The avionics compartment of the Global Hawk is presently cooled by pumping fuel through the compartment. The proposed system will keep the fuel out of the avionics compartment and also increase operating margins for end-of-mission conditions.