Loop Heat Pipe (LHP) has been the leading two-phase heat transport technology for space-based thermal control subsystems (TCS) for more than 20 years. LHPs are capillary-pumped devices having no mechanical moving parts to wear out or break down. Due to the excellent phase-change heat transfer efficiency, for the most part, two-phase loops are lightweight and more compact than the single-phase counterparts. Hence, it has become popular among the thermal engineers for the operational reliability, robustness, long life, and more importantly, requiring no maintenance. Nevertheless, after more than two decades in service, the thermal requirements imposed on the TCS by the ever-increasing demand for the payload power are finally outpacing the LHP capability. Sintered metal powder wicks of todays technology generate a maximum capillary pumping head of about 5psid with Ammonia as the working fluid. Nominal room-temperature Ammonia LHPs have heat transport capacities of approximately 5kW-m, which is sufficient for most space-based TCS at the present. However, the NASA Artemis program in which an astronaut lunar base camp is planned shall require the heat management in excess of hundreds (if not thousands) of kilo-Watts over long distances. In addition, the lunar human base includes many heat-dissipating equipment situated at far-apart locations. The heat collection would be a serious challenge for a single-evaporator LHP for it has only one heat collection site with a limited external surface to interface the heat source. Hence, more capable heat transport technologies (with multiple evaporators and condensers) need to be developed and flight qualified quickly to achieve the Technology Readiness Level (TRL) of 7-8 for the LHP replacement in 10-20 years. Anticipated
Benefits: The proposed cooling technology employs a magnetic levitation impeller pump to provide fluid circulation in a hermetically-sealed closed loop. It has only one moving part - the impeller. Hence it is highly reliable and durable for manned or unmanned space nissions. Potential applications are the thermal control systems (TCS) for spacecraft or to support the planned human habitation on the Moon or Mars. Specifically, megawatt cooling technologies shall be needed for spaced-based high energy propulsion, conversion and storage. The proposed technology is perhaps ultimately necessary for the development of all-electric platforms that the U.S. Department of Defense advocates for the near future from aircraft, ships/submarines, railguns. The heat dissipation for these systems may reach several megawatts.
