Paragon Space Development Corporation (Paragon) will address NASA’s Z2.01 Spacecraft Thermal Management objective by developing and prototyping the Smart Passively Articulating High-turndown Radiator (SPAHR). The SPAHR concept has a base turndown capability of at least 13:1, with the potential of up to 43:1 using a propylene glycol/water (PGW) working fluid, providing unique capability to support crewed exploration with a non-hazardous working fluid. The two orientations of the SPAHR radiator are ideally suited for the operational heat loading (6-8 kW) and dormant loading (1-2 kW) as called out by the solicitation. The SPAHR capability also more than meets the stretch goal of 12:1 identified in the NASA technology roadmap TA14.2.3. This turndown capability is of the radiator device only; in a Thermal Control System (TCS) SPAHR turndown ratios can exceed the 50:1 goal in TA188.8.131.52 for Variable-Geometry Radiator. This very high turn down enables human exploration well beyond our present capabilities and enables single-loop thermal control of a crewed vehicle with a non-toxic fluid, which reduces TCS launch mass by 25% or more due in large part by eliminating the need for the external pump package.
SPAHR actuates via through solid-state, temperature dependent two-way shape memory torque tube. This actuation varies the view of radiator panels that also employ selective emissivity faces; the combination of which provides the high turndown. The shape memory torque tube is actuated by the working fluid temperature alone. No active control, instrumentation, or power is required; the passive nature of its behavior makes for a highly dependable and robust thermal control mechanism and decreases the complexity and mass of control systems that would otherwise be required to orient the radiators. When in its highest heat rejection configuration, SPAHR’s mass and heat rejection per unit area are on par with state-of-the-art conventional flat panel radiators.
SPAHR is applicable to future human exploration systems, habitation systems, and to satellite systems. In Technology Area (TA) 184.108.40.206 of NASA’s 2015 Technology Roadmap, NASA identifies the need to develop variable heat rejection radiator technology that can achieve a turndown ratio of 12:1 (stretch goal) with an even higher performance goal of a 50:1 turndown ratio possible. SPAHR will surpass the stretch goal and contribute substantially toward achieving to the higher performance goal.
SPAHR applies to vehicles, satellites, and habitats requiring pumped fluid loop radiators including large portions of the DOD and commercial satellite market. Elements developed for SPAHR are extensible to multiple radiator architectures not just the application described here. SPAHR has potential application as a lightweight, operationally responsive radiator for terrestrial DOD applications.