A Compact, Gravity-Insensitive Gas Trap for Extreme Temperature Environments

NASA is working toward missions involving crewed habitats for extended stays within orbital platforms. Environmental control of these habitats is enabled by use of thermal control systems to maintain conditions within a tight temperature band. These thermal control systems must be highly reliable, lightweight, and able to effectively control cabin and equipment temperatures to within several degrees under varying heat loads in conditions of low gravity. For existing spaceborne habitats and survival of payloads, thermal control is established by pumped liquid coolant loops, often employing low-surface-tension fluids. Ensuring reliable operation of the coolant pump is paramount; methods to reduce operational risk to the pump are needed to enable long-term human presence. To address this need, Creare has developed a compact, gravity-insensitive gas trap capable of passively sequestering, then venting non-condensable gas buildup in liquid coolant loops with low surface tension fluids. In Phase I, we proved the feasibility of this approach by developing a preliminary gas trap design, demonstrating key processes involved in fabrication of the gas trap including development of novel microporous materials. We assembled a subscale dual-membrane gas trap and characterized its performance through laboratory testing. This allowed us to demonstrate that the gas trap accumulates gas, can passively vent to a coolant loop accumulator gas manifold, and ultimately to the cabin. In Phase II, we will further develop the gas trap technology through expanded trials, we will fabricate a full-scale gas trap capable of serving a multi-kW spaceborne thermal coolant loop, demonstrate its steady state and transient performance in a laboratory coolant loop. We will then conduct microgravity flight tests of the gas trap within an aerated coolant loop, using our anticipated concept of operations. Finally, we will deliver the prototype to NASA for further performance evaluation. The overall project goal is to develop a lightweight, low maintenance, gravity-insensitive gas trap for accumulation of trapped non-condensable gas in spaceborne coolant loops circulating low surface tension fluids. Our technical approach is to develop a dual membrane gas trap featuring both hydrophilic and superhydrophobic microporous titanium alloy tube structures. The specific innovations include (1) the use of novel microporous hydrophilic material treated with FLSP techniques to enhance bubble point with negligible impact to liquid permeability; (2) the use of novel microporous superhydrophobic material treated with FLSP techniques to enhance liquid entry pressure with negligible impact to gas permeability; (3) the unique design layout including an inlet separation stage and gas accumulation core, and (4) the development of a concept of operations for the gas trap venting that eliminates large pressure gradients on porous materials. In Phase II, we will work with NASA and our partner, Sierra Space, to further develop, demonstrate, and lay the groundwork for commercialization of the gas trap technology. Our proposed effort includes the following specific technical objectives: (1) We will conduct further work to further optimize hydrophobic and hydrophilic structures in small scale trials with larger sample size, then extend the process to processing of external hydrophilic and hydrophobic tube structures; (2) With this process developed, we will fabricate a full-scale gas trap capable of serving a multi-kW spaceborne thermal coolant loop; (3) We will demonstrate its steady state and transient performance over a wide range of conditions in a laboratory coolant loop with bellows-type accumulator. The loop will be suitable for installation onto a parabolic flight for microgravity testing; (4) We will then conduct microgravity flight tests of the gas trap within the aerated coolant loop, using our anticipated concept of operations, aboard a series of parabolic flights to advance the technology to TRL-6 (ie, demonstration in a representative environment). Finally, we will deliver the prototype to NASA for further performance evaluation.

Gas traps are needed for enhanced reliability in thermal control for NASA missions including on-board the ISS. The current proposed effort would enable high reliability coolant loops for use in future lunar habitats or extreme environments circulating low-surface-tension fluids. Other governmental applications (e.g., DoD) are similar to NASA uses, specifically high reliability coolant loops operating in extreme environments for aircraft, ships, and ground vehicles. The superhydrophobic membrane development has commercial applications for various chemical industries including steam separation and chemical processing with two-phase caustic chemical flows. The gas trap itself has application in high reliability coolant with minimal available maintenance such as in nuclear power plants or in other remote power stations.

This is early/mid-stage (TRL 4) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

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