Radiator panels are the baseline heat rejection approach for most space systems. This approach is sound, but requires a large amount of surface area to radiate the anticipated heat load. The large panels require support structures to hold them in place and prevent damage. These structures impact mass and cost. Additionally, it is not practical to launch, transport, integrate, and relocate large panels as monolithic units. For this reason, a foldable scissor assembly is envisioned to stow the panels compactly and extend them before system startup. The moving parts and flexible fluid connections required for this approach add complexity and potential failure modes to the system. Some mission plans also require power system mobility for exploration well beyond the base camp. For this scenario, the radiator assemblies must be retracted, stowed, and redeployed each time the system is moved. These activities require time and effort, and they expose the radiator panels and associated mechanisms to damage risk. Even when properly stowed, the relatively thin panels could be damaged during transportation.

The innovation is an ultra-compact heat rejection system comprised of a high-speed axial-flow fan and microtube heat exchanger modules. Fundamentally, the approach relies on forced convection instead of radiation heat transfer, which makes the system much more compact than conventional radiator panels. Additionally, this approach can eliminate intermediate pumped liquid loops if gas from the system being cooled passes directly through the fan-cooled heat exchanger instead of through a separate liquid-cooled unit. The resulting technology will reduce operating temperatures while decreasing heat rejection system size and mass dramatically. This outcome will enable better performance for a broad range of applications, and make them more affordable and practical to launch, deploy, and relocate.

The low atmospheric pressure on Mars, other planets, and moons beyond Earth is a key factor that impacts the design. In particular, the fan must provide a high volumetric flow rate because the ambient density is low. The primary challenges are to (1) develop a compact fan that provides a high volumetric flow rate with low power consumption, (2) produce compact heat exchanger modules with low mass and low pressure losses, and (3) ensure reliable, long-life operation without maintenance.

The proposed heat rejection system will enhance ambient cooling for an extremely broad array of applications. Compact, high-reliability cooling is universally desirable and will be adopted wherever it is economically practical. The most significant benefits associated with this approach are compact size, low mass, low power consumption, operation in any orientation, dust tolerance, zero maintenance, and long life. HVAC systems, mobile electric generators, aircraft, land vehicles, and watercraft are all potential applications with military, industrial, commercial, and residential markets.

This work was done by Marc Gibson of Glenn Research Center, and Jeffrey Breedlove and Thomas Conboy of Creare, LLC. NASA is seeking partners to further develop this technology through joint cooperative research and development. For more information about this technology and to explore opportunities, please contact This email address is being protected from spambots. You need JavaScript enabled to view it.. LEW-19374-1