Description: Innovative aspect: The morphing radiator uses SMAs to passively change its heat rejection area (opening/closing its cylindrical panel). The concept can provide high turndown: >12:1 with a single loop active TCS. During FY16 a composite radiator panel was developed, and demonstrated actuating with SMAs in ambient and thermal vacuum environments.FY17 objective: Develop an entire practical radiator design and produce a subscale segment of a multi-panel radiator with the following approach: 1) Create custom SMAs to open/close the radiator at the hot/cold cases expected by a single loop active TCS for a manned spacecraft (cis-lunar/mars missions). 2) Integrate the SMAs into the radiator panel design. 3) Develop a processing method to bond SMAs to the radiator face sheet. 4) Develop a robust method to bond the radiator panel to its flow tube. 5) Build upon existing analytical tools to expedite radiator design. Next steps after FY17 work: 1)System-level ground test on the produced radiator. 2)Investigate methods to provide a low absorptivity/high emissivity coating of the radiator panel. 3)ISS express pallet flight demonstration. Comparison to other variable heat rejection approaches: As opposed to stagnating, freezable, and digital radiators, this concept does not require emptying/refilling of passages (which risks freezing upon refilling), or modification of the radiator fluid's state (recovering from freezing/stagnating can be very slow and difficult to predict). JAxA/ISAS developed and thermal vacuum tested a passive SMA actuated flat radiator panel for a 100W class satellite [Nagano and Nagasaka 2006].

Benefits: Technology need for future crewed Mars missions: Variable heat rejection radiators that 1) enable a single-loop manned spacecraft thermal control system (TCS) (lowers system mass/complexity and improves crew safety), 2) maintain a TCS with a maximum to minimum heat rejection ratio (i.e. turn down ratio) of 12:1 (EMC target need is 12kW of heat rejection at ~220K and 1kW at ~0K.), and 3) improve TCS reliability. State-of-the-Art: Dual loop TCS with oversized radiators and an external flow loop with a toxic low freezing point fluid that connects to a non-toxic inner cabin loop via an interface heat exchanger. This TCS architecture is employed in Orion and can achieve a 3:1 turndown ratio. Design concepts for cis-lunar habitats have employed a dual-loop architecture with a regenerative heat exchanger to achieve a 8:1 turndown ratio.