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A thermal management concept providing high heat flux capability for High Power Microwave (HPM) source devices used in Directed Energy Weapon (DEW) Systems is presented. Obstacles to the practical application of DEW to aircraft require effective solutions to high heat flux thermal management. Our approach utilizes enhanced cooling mechanisms (subcooled nucleate flow-boiling) coupled with an optimized cooling channel geometry fully integrated within the HPM source device structure. The concept developed has demonstrated effective cooling for heat fluxes up to 900 W/cm2. The design and integration of our thermal management system with HPM source hardware is presented. In addition, experimental testing validating the thermal capability and demonstrating the overall operation of the HPM pulsed-power system is discussed.

An innovative thermal management system (TMS) that provides both effective active heat transfer and high passive thermal energy storage capacity has been developed and successfully demonstrated. The TMS integrates the high latent heat advantages of a phase change material with an actively cooled cold plate design. The resulting TMS concept has direct use on many transient system applications, where the amount of heat dissipated varies over time. The example discussed in this paper is the transient operation of electric flight control actuator hardware that is proposed for the More Electric Aircraft (MEA) Initiative. The development of the TMS concept, the successful fabrication and validation testing on actual flight control electronic hardware is provided. The advantages of the Thermal Management System include: significant weight savings, high thermal performance, high thermal energy storage capability, high reliability and reduced maintenance.

An advanced composite housing for the F/A-18C/D Generator Converter Unit (GCU) has been developed. The composite housing directly replaces the existing aluminum housing, and provides lighter weight and improved thermal performance. The composite housing uses IM7/954-2A material, with embedded aluminum pin fins in selected areas for thermal management. A fabrication procedure for the composite housing was developed, using matched metal compression molding, with adhesive bonding of secondary components. Two prototype housings were fabricated and will be tested for qualification.

This paper provides an overview of the development of an organic matrix composite housing for an aircraft generator. The specific component discussed is the main housing for the F/A-18 C/D Generator Convenor Unit (GCU). This component fulfills both structural and thermal functions. The composite housing will be a direct replacement for the existing aluminum component, and will offer lighter weight and improved thermal performance, at a comparable cost. The composite housing will be consolidated by matched metal net molding, and will demonstrate the use of embedded metallic pin fins within the composite material to improve thermal performance. The paper addresses the design development, thermal and structural design verification analyses, material compatibility testing, and fabrication process development and tooling design.

Supercritical cryogenic hydrogen is being considered as a coolant for certain high heat flux thermal management applications, including hypersonic vehicles such as the National Aero-Space Plane and high power spacecraft systems for the Strategic Defense Initiative. The safety issues associated with hydrogen make testing with this coolant difficult and costly. Supercritical cryogenic helium is an attractive alternate coolant for prototype component testing. This paper presents a comparative analytical study of the behavior of supercritical cryogenic hydrogen and helium coolants. A detailed three-dimensional finite element analysis of a coolant channel in a test panel was used to compare the calculated heat transfer coefficient and panel temperatures for four different, commonly used turbulent flow heat transfer coefficient correlations for supercritical hydrogen and helium.