Active Thermal Switching OHP Radiator for Lunar Science

The number one shortfall identified by NASA technology is the ability to survive and operate through the lunar night. ThermAvant Technologies (TAT) proposes a freeze-tolerant thermal switching Oscillating Heat Pipe (OHP) assembly using a low toxicity working fluid and freeze tolerant azeotrope working fluid to address the challenge posed by S16.05. NASA SBIR S16.05 calls for new capabilities in thermal management for long-duration lunar science, especially focused on surviving the lunar night with temperature excursions as low as -213°C for as long as 14 days, with low toxicity radiator working fluids, and gravity independent performance. TAT proposes to demonstrate the following capabilities not found in State of the Art (SOTA) radiator systems: Thermal conductance ratio of ON to OFF (or turn down ratio) in excess of 600:1. 240:1 has been demonstrated by TAT under a privately funded effort. TAT radiator panels will have a reservoir into which working fluid may be condensed (emptying the OHP and lower conductance) when an OFF condition is desired. This fluid reservoir will be managed with low power heaters to ensure reservoir stays warmer than the OHP when an ON condition is required and by turning the heaters off to allow reservoir to cool below radiator temperature and begin condensing fluid into the reservoir when OFF condition is desired. Calculated conductance in case study (ref Fig 1), is 2.27 W/K when the OHP is ON and 0.0033 W/K when OFF resulting in 688:1 predicted turn down ratio. This will be achieved with a 58% reduction in specific mass and 62% reduction in areal density compared with SOA radiator systems increasing lunar science SWaP-C as reduced mass reduces launch costs.