Adaptive Thermal Management System

NASA’s envisioned Lunar and Martian surface operations will require constant and reliable power systems. Traditional power architectures, including solar cells and batteries, cannot be solely relied upon due to the lengthy lunar nights and challenging thermal environments. How-ever, fuel cells, including primary fuel cells and regenerative fuel cells, represent a promising means for energy generation and storage on planetary and lunar surfaces. PaCeSS could further improve mission flexibility by significantly enhanc-ing reliability and longevity with fully passive fuel cell power generation capability. Test systems have been built to validate the performance characteristics of various PaCeSS technology elements, and many of the component materials have already been characterized. Some of these novel technology elements already demonstrated include a two-phase thermosyphon operation in fuel cell conditions, a passive shape memory actuator operation using two-phase water, and a shape memory alloy radiator turndown. Although the current design of the shape memory alloy actuated rad-iator system is dependent on partial gravity and space-like environments where heat rejection is performed primarily via radiation, there may be ways of using the same basic system for controlling fuel cell temper-ature via convective heat rejection for terrestrial applications. Addition-ally, other elements of this concept could be commercialized terrestri-ally, including the thermosyphon heat transport mechanism, a multi-purpose vapor chamber, and a thermal management system that uses water by-product as the thermal management medium. The Passive Fuel Cell Surface Power System is at a technology readiness level (TRL) 3 (analytical and experimental critical function and/or characteristic proof of concept) and is now available for patent licensing. Please note that NASA does not manufacture products itself for commercial sale.

Prototype thermal control valves for the next generation spacesuit were challenged in maintaining precise thermal control, so engineers created a design that functions like a traditional ball valve but added tapered-valley contours to the ball that yields a variable orifice which is more predictable at controlling flow. The key differences between the TCBV and traditional v-channel ball valves are that this technology has one inlet and two outlets allowing the split-flow of fluids whereas traditional v-channel valves only have one inlet and one outlet. Additionally, traditional v-channel ball valves don’t enable the full flow rate of a given system while this technology does. The ball valve is held in place within the TCBV using two PTFE seats compressed by spring-loaded side plates. The hole in the middle of the ball valve and adjoining tapered valleys mate with the PTFE seats to create varying sized orifices depending on valve position. Specially designed O-ring seals surrounding the ball valve assembly allow the seats to move within the pocket while preventing internal leakage. In this technology’s spacesuit application, coolant is fed to the ported ball valve where the coolant is apportioned to each valve housing exit either primarily feeding the cooling and ventilation garment or the bypass circuit back to the spacesuit’s thermal cooling system. The apportionment is determined by the astronaut’s manual valve adjustment or automatically by the suit.

One inner insulative layer, and one outer robust ablative layer comprise the AMTPS technology. When applying the heat shield to the surface of a spacecraft, the insulative layer is printed first and primarily functions to reduce the amount of heat soak into the vehicle. The formulation of the insulative layer has a slightly lower density (as compared to the robust layer) and is adjusted using a differing constituent ratio of phenolic and/or glass microballoon material. Both formulations combine a phenolic resin with various fillers to control pre- and post-cure properties that can be adjusted by varying the carbon and/or glass fiber content along with rheology modifiers to enhance the fluid flow for deposition systems. The robust layer is applied next and functions as the ablative layer that ablates away or vaporizes when subjected to extremely high temperatures such as those achieved during atmospheric entry. The formulation of the robust layer produces a gas layer as it vaporizes in the extreme heat that acts as a boundary layer. This boundary prevents heat from further penetrating the remaining robust material by pushing away the even hotter shock layer. The shock layer is a region of super-heated compressed gas, positioned in front of the Earth-facing bottom of the spacecraft during atmospheric entry, that results from the supersonic shockwave generated. Commercial space applications for this AMTPS technology include use on any spacecraft that transits a planetary or lunar atmosphere such as Mars or Saturn’s moon Titan. Additionally, the invention may be useful for launch system rockets to provide heat shielding from atmospheric reentry or to protect ground equipment on the launch pad from rocket exhaust plumes. As the number of government and commercial space missions to primary Earth orbits, the Moon, and the Solar System increase, there will be a growing need for cost-effective, on-demand, and timely fabrication of heat shields for space-related activities. AMTPS Formulations – Insulative and Robust Variation is at a technology readiness level (TRL) 5 (component and/or breadboard validation in laboratory environment) and is now available for patent licensing. Please note that NASA does not manufacture products itself for commercial sale.

NASA's TVS Augmented Injector includes an internal heat exchanger, a fluid injector spray head, and an external surface condensation heat exchanger - all combined with multiple intertwined flow paths containing liquid, two-phase, and gaseous working fluid. The TVS provides a source of coolant to the injector, which chills the incoming fluid flow. This cooled flow promotes condensation of the tank ullage dropping pressure and maintains incoming fluid flow. The system eliminates the potential for a stalled fill condition and reduces tank pressure during cryogenic fluid transfer. During fill operations, the tank vent can be closed early in the process before fluid is introduced, and, in some cases, the tank vent may not even need to be opened. Furthermore, the TVS Augmented Injector can remove sufficient thermal energy to reach a 100% liquid level in the receiver tank. A cryo-cooler can be used in place the TVS flow circuit for a zero-loss system. The TVS Augmented Injector couples internal fluid flow cooling and external surface ullage gas condensation into a single, compact package that can be mounted to small tank flanges for minimal impact insertion into any vessel. The injector is printed as one part using additive manufacturing, resulting in part count reduction, improved reproducibility, shorter lead times, and reduced cost compared to conventional approaches. The injector may be of particular interest in applications where cryogenic fluid is expensive, fluid loss through vents is problematic, and/or achieving high filling levels would be helpful. The injector can benefit typical cryogenic fluid transfer between containers or, alternatively, can serve as a tank pressure control device for long-term storage using a fluid recirculation system that pumps fluid through the injector and sprays cooled liquid back into the tank. Additionally, where ISRU processes are employed, the injector can be used to liquefy incoming propellant streams.

Advances in new polymers and composites along with growing industrial needs in below-ambient temperature applications have brought about the Macroflash development. Accurate thermal performance information, including effective thermal conductivity data, are needed under relevant end-use conditions. The Macroflash is a practical tool for basic testing of common materials or research evaluation of advanced materials/systems. The Macroflash can test solids, foams, or powders that are homogeneous or layered in composition. Test specimens are typically 75mm in diameter and 6mm in thickness. The cold side is maintained by liquid nitrogen at 77 K while a heater disk maintains a steady warm-side temperature from ambient up to 373 K. The steady boiloff of the liquid nitrogen provides a direct measure of the heat energy transferred through the thickness of the test specimen. Nitrogen or other gas is supplied to the instrument to establish a stable, moisture-free, ambient pressure environment. Different compression loading levels can also be conveniently applied to the test specimen as needed for accurate, field-representative thermal performance data. The Macroflash is calibrated from approximately 10 mW/m-K to 800 mW/m-K using well-characterized materials.