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Completed TRL 2 (started at 3, targeting 5)
Project Objective
Breadboard demonstration (and associated math model) of an advanced single phase, pumped loop thermal radiator innovation utilizing a serpentine flow path with highly thermal conductive face-sheets is proposed for Moon-to-Mars surface, transit, habitation and lander missions.
Project Description
Pumped loop radiators are commonly used to reject large amounts of heat associated with crewed spacecraft. The State of the Art (SOA) for crewed systems is represented by the International Space Station (ISS) External Heat Rejection System (HRS) Thermal Radiators. The ISS HRS utilizes a manifold design with many parallel flow paths coupled to thin face-sheets and low viscosity ammonia as the working fluid, which may not be preferred for future missions due to toxicity concerns. Although contemporary coolant choices provide lower freezing points, the current SOA design may not be well positioned to provide both sufficient heat transfer and manageable pressure drop due to adverse fluid thermo-physical properties, including viscosity.
A serpentine flow pattern, commonly used in two-phase systems may better balance the two competing demands for heat transfer and pressure drop. A highly conductive pyrolytic graphite layer would be added to the face-sheet in the breadboard radiator for improved efficiency.
Project goals are to develop an advanced thermal radiator breadboard optimized to offer lower mass, improved performance, improved failure tolerance and greater compatibility with current coolant choices over the SOA.
Correlated thermal math-models to predict radiator performance will also be developed to parameterize performance and mass for the serpentine geometry (height and cross-sectional area) and working fluids.
Total other direct costs (ODC) of $34k are allocated to the project for the procurement of raw materials, a fluid pump, instrumentation, a heat exchanger and costs associated with fabrication and consumables needed for thermal vacuum testing.
Project Results and Conclusions
The project is scheduled for completion in the 1st quarter of CY25. Radiator thermal model development, design of the test article and procurement are complete.
Modeling and hand calculations were used to size the pump required for the test setup using Galden HT170 and a 2x5ft serpentine radiator with 8 passes (along long edge) of 3/8" outer diameter (OD) tubing. A detailed SINDA/FLUINT (Systems Improved Numerical Differencing Analyzer/Fluid Integrator) model was completed in Thermal Desktop to consider heat transfer and pressure drop in the serpentine radiator and to aid in the design optimization of the radiator.
The thermal model allows for investigating the impacts of using alternate transfer fluids. As part of the model development, a tool was developed utilizing the OpenTD API (Open Thermal Desktop Application Program Interface) that allows for building thermal radiator models quickly, with easier variation of design parameters such as panel dimensions, tube spacing, and passes of the tubing within a serpentine radiator.
Also finished procurement of hardware and materials needed for the construction of a radiator, fluid loop, and testing instrumentation in preparation for a Thermal VAcuum Chamber (TVAC) test of the serpentine radiator with Galden fluid. Fabrication of the radiator will be accomplished via brazing the tubing onto the radiator face-sheet.
An advanced thermal radiator, optimized to provide lower mass, improved performance, improved failure tolerance and greater compatibility with current coolant choices could be an enabling technology for future NASA exploration missions, including Lunar/Mars Surface & Transit Habitation, Lunar/Mars Surface Fission Power, In-Situ Resource Utilization (ISRU), Landers, Rovers and other high-power assets.
Developing advanced Thermal Control System (TCS) technology will well position MSFC to participate in the many facets of NASA’s Artemis Program and provide substantial technology.
This investment will provide hands-on experience and skill enhancement for EV30 engineers, particularly early career employees, in the discipline of thermal engineering.
This investment will also provide enhancements to the MSFC HI-TTeMP thermal laboratory as well as provide the capability to formulate and propose future TCS related development projects.
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