Description: Future human spacecraft will venture far beyond the relatively benign environment of low Earth orbit. They will transit through the deep space, but they may encounter warm transient environments such as low lunar orbit. Some spacecraft elements may be launched untended and would operate at relatively low power levels as they transit to their final destination. The combination of extreme environments and high turndown capability will be a major challenge for spacecraft thermal control systems. Thermal switches are among the thermal control devices that are required and can dissipate a wide range of heat loads in widely varying environments while using fewer of the limited spacecraft mass, volume and power resources. This SBIR project proposed by ACT will develop a low mass and high conduction ratio two-phase thermal switch as a thermal control system component for human spacecraft. The proposed device could work in thermal switch regime or in variable conductance regime while the set point can be changed remotely. A trade study will be conducted to define the three features of the low mass two-phase thermal switch and demonstrate the feasability of the concept. A preliminary full scale prototype will be designed, fabricated and tested at the end of the Phase I program.

Benefits: A major objective of the NASA science spacecraft systems development programs is to implement science measurement capabilities using small, affordable spacecraft enabling a single spacecraft to meet multiple mission requirements thus making the best use of the limited resources. Another objective of NASA is to extend human presence in the solar system. To accomplish these objectives, NASA is seeking for innovations in thermal control technologies to enable further scientific advancement at lower cost, lower risk, reduced power requirement, reduced volume, and/or reduced mass, while maximizing the lifetime, safety and reliability. The proposed low mass two-phase thermal switch (TPTS) technology shows great potential by reducing the complexity, mass and cost of previous devices while increasing the performance. The program will demonstrate the feasibility of modeling, designing, optimizing and manufacturing of such a high performance TPTS. NASA Orion Crew Exploration and Deep Space are among NASA's programs to benefit from this innovation.

The Low Mass Two-Phase Thermal Switch developed by this program can be used for both space and terrestrial applications. It can practically be implemented and used by other military or commercial satellite applications that require infrared imaging and sensors on advanced telescopes, such as Air Force Space-Based Infrared (SBIR) surveillance and tracking system architecture. For example, through the use of cryogenic thermal switch technology, the infrared sensing capability can be enhanced by reducing the parasitic heat load. Also, the device can be easily designed be used as thermal control component for any terrestrial application, both military and commercial.