Innovative, Lightweight Methods For Thermal Management of HEL Mirror Subsystems

The Air Force (AF) is interested in innovative, unique approaches for thermal management of HEL mirror subsystems which include active and passive methods for both web-based and foam-core lightweighted mirrors.  Optical Physics Company (OPC) proposes to investigate three (3) active methods for cooling foam-core lightweighted mirrors in which flows of He or another gas, water and water with phase changing wax through the foam-core mirror will very rapidly remove the energy deposited (180 KJ to 6 MJ over 100 seconds) such that the temperature of the optical surface will rise very minimally.  In fact, all of these cooling approaches can provide a steady state solution for a matching laser irradiance on a lightweight silicon carbide or silicon foam-core HEL optic.  .   During Phase I, OPC will use a model of a flat 5 diameter, 0.6 thick lightweight silicon carbide optic with a 100 pore per inch foam-core for CFD and thermal analyses of the 3 active cooling methods.  A test optic will be manufactured and used to demonstrate the thermal management technology with open-loop water cooling.  If Phase I is successful this optical thermal management technology would achieve TRL 4-5. BENEFIT: A complete prototype closed-loop thermal management system would be demonstrated in Phase II.  This system would include a compact, lightweight refrigeration/metal foam-core heat exchanger subsystem and would achieve TRL 6.  In Phase III and beyond, OPCs compact, lightweight thermal management system would be upgraded to be field deployable and modified as required for application to other AFRL HEL programs and other commercial functions where heating occurs.  The military applications include cooled mirrors for Relay Mirror systems, Advanced Tactical Laser and mobile THEL.