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Spray Cooling

High-Power Microwave Amplifiers

Mainstream recently completed a highly successful project to demonstrate the benefits of spray cooling high-power microwave amplifiers (device-level) used in solid-state, phased array transmitters/receivers. Heat flux removal rates in excess of 100 W/cm2 were achieved at wall superheats less than 12 K, using inert, dielectric refrigerants. Amplifier output power was increased by 37%, and efficiency was increased by 14%. Although these results are significant in laying the groundwork for an integrated spray cooling system for phased array antennas, additional work must be performed to optimize the spray system and increase reliability of the thermal/electrical system.

Mainstream engineers, along with our commercial radar partner, are working to demonstrate the benefits of spray cooling a multi-channel transmitter (module-level). Based on prior experimental work, we expect a 40% increase in power output, a 30% increase in efficiency, and an order of magnitude increase in reliability.

This enabling thermal technology has immediate application to MDAs Medium Extended Air Defense, Theater High Altitude Area Defense, Ground-Based Midcourse Defense, Sea-Based Midcourse Defense, and Advanced Concepts Programs. In addition, the technology can be extended to other high-heat, flux-cooling applications, including MDAs Airborne Laser, Space-Based Laser and Kinetic Energy Laser Programs.

Solid-State Lasers

Industrial-sized, solid-state lasers cannot be scaled up in power to meet the demands of future missile defense systems due to stringent thermal constraints. Existing water-based thermal management systems are undesirable because water has a high freezing point and the military systems need to operate in low-temperature environments.

Mainstream recently verified experimentally the potential for spray cooling high-power laser diode arrays with non-water-based fluids. This patented system is capable of removing high heat flux at the laser diode array, maintaining a spatially uniform temperature over large laser slab surface areas, and accurately controlling laser temperature.

A complete spray cooling thermal management system is now being designed, fabricated, and integrated into a high-power, solid-state laser. Next, the performance of the integrated laser system will be tested. Gravity-independence will be demonstrated for adverse-gravity and space-based applications. The result of this program is not just an incremental improvement over an existing thermal solution. It is the enabling technology that will make laser defense systems a reality.