Freeze Tolerant Water Heat Pipe and Thermal Switch

unar night poses a significant thermal challenge to small, low power payloads, rovers and landers. Due to the slow rotation of the lunar surface, the environmental temperature drops to below 100K for approximately 14 earth days. In order to enable long duration science missions on the lunar surface it is necessary to maintain the electronics above survival temperature during the lunar night. This requires thermal management technology with high turndown ratios, capable of rejecting waste heat during the hot lunar day and minimizing heat leaks during the lunar night. Other key features include passive operation, high reliability, and lightweight. Variable conductance heat pies (VCHP) and thermal switches can achieve many of these goals but come with drawbacks. For example, ammonia VCHPs require bulky reservoirs of gas and stainless-steel envelopes to achieve the high turndown ratio, and many thermal switches are limited in how much power they can transport. In this SBIR program, Advanced Cooling Technologies will develop a freeze-tolerant water-based heat pipe that uses freezing of the working fluid as a thermal switching mechanism to provide a high turndown ratio (>1000:1). ACT’s innovative approach to freeze tolerance will enable the heat pipe to survive an indefinite number of freeze/thaw cycles without experiencing damage due to the expansion of freezing water. The thermal switching feature enabled by freezing the working fluid results in a highly versatile thermal management device with many advantages for lunar applications as well as other space missions and terrestrial uses. The highly variable temperature environment of the lunar surface presents a significant challenge to small, low power payloads, landers, and rovers. An ideal thermal control device for this application has a very high turndown ratio, high heat transport capability, is passive, and lightweight. A water heat pipe can carry more power than other working fluids and provides a natural thermal switch at low temperatures due to the freezing temperature of water; however, water is typically excluded because of damage caused by expansion of water during freezing. Advanced Cooling Technologies, Inc. (ACT) will develop a freeze tolerant water heat pipe that uses freezing of the working fluid as a thermal switching mechanism. Freeze tolerance is achieved by using a non-azeotropic binary mixture of water and an anti-freeze compound. A small amount of an anti-freeze compound can prevent damage caused by volumetric expansion of water during freezing while having a minimal impact on heat pipe performance. This concept addresses NASA’s top identified technological shortfall of lunar night survival.

The immediate NASA application of the proposed heat pipe technology is in enabling long duration missions on the lunar surface for small, low power payloads, rovers and landers. These missions require variable heat rejection thermal control systems to allow for operation throughout the complete lunar cycle, and the ability to remain above survival temperatures when powered down during lunar night. Many current, near and long-term missions could benefit from this system including many of the payloads selected as part of the NASA CLPS program. The proposed heat pipe technology is of interest to commercial space companies which are focused on developing unmanned and manned probes for lunar exploration as well as exploration of other similar planets or moons. ACT plans to reach out to commercial companies like Astrobotic Inc., FireFly Inc., Blue-origin, Intuitive Machines and others to seek non-NASA applications for this technology.

This is a mature technology (TRL 7+) — the realistic path in is usually NASA's Technology Transfer Program: licensing an existing NASA patent, or a Space Act Agreement to use NASA facilities/expertise directly. NASA also runs a startup licensing program with no upfront fee for companies formed to commercialize a specific NASA technology.

None of these are guaranteed paths for this specific project — TechPort itself doesn't have an "apply" button. Reaching out to the contact(s) above with a specific question is usually the fastest way to find out what's actually open.