NASA’s plans to further expand human and robotic presence in space and planetary surface automatically involve significant thermal challenges. A hot reservoir variable conductance heat pipe (VCHP) that can provide much tighter passive thermal control capability is an ideal thermal management device for future planetary landers and rovers. Based on previous ISS test results, advanced fluid management features and strategies are the key to maximize hot reservoir VCHP’s reliability during long-term planetary exploration missions. In STTR Phase I, Advanced Cooling Technologies, Inc. (ACT) in collaboration with Case Western Reserve University (CWRU) performed a fundamental study to understand the complex fluid transport phenomena within a hot reservoir VCHP. A Loop Hot Reservoir VCHP (LHR-VCHP) concept was devised during the program. With the novel loop configuration, two mechanisms to induce a net transport flow for VCHP purging (i.e. removal of working fluid from the reservoir) were identified: (1) by momentum transfer from vapor to NCG through shearing (2) by filtering the pulses (via a Tesla/check valve) generated in the heat pipe section of VCHP loop. The existence of momentum transfer flow and its effectiveness on VCHP reservoir purging were demonstrated through modeling and experiment. In Phase II, ACT-CWRU team proposes to further mature the LHR-VCHP technology and demonstrate its reliability by maximizing the flow rate induced by the two mechanisms stated above. Phase II work plan will include systematic studies of both momentum transfer induced flow and pulses generation and filtering induced flow within a loop VCHP, development of fluid diodes for pulses filtration, design and optimization of LHR-VCHP prototypes based on the two mechanisms. At the end of the program, a prototype-flight LHR-VCHP for planetary landers and rovers thermal management will be developed based on the best solution that potentially could result from both mechanisms combined.
The next generation of Lunar rovers and landers require variable thermal links. A hot reservoir VCHP with established reliability is needed since it is able to operate during large tilts, shut down during the long Lunar night and maintain the payload temperature nearly constant over wide sink temperature fluctuation on the Lunar surface. The LHR-VCHP technology developed under this STTR will benefit the Artemis program, which envisions to establish a sustainable presence on the moon by 2028.
Non-NASA applications include commercial landers involved in lunar exploration. UAVs can also benefit from the developed technology under the proposed program. ACT already works prime contractors to develop thermal control systems for their UAVs. The new Hot Reservoir VCHP provides superior thermal control over the currently used solution that is based on cold biased reservoir VCHP.