Lightweight Compact Deployable Radiator

Project Objective  

Create a flexible deployable radiator for small satellites.

Project Description 

The goal of this project is to develop a lightweight, compact, deployable radiator that can be used to sink heat for small satellites. The project was awarded for $29.6k in procurement money; 0.25 WYE; and 0.35 FTE for a year to experiment with the production and testing of this lightweight; compact radiator concept. We constructed the radiator's core technology (flexible heat pipes) using a few different processes and tested the conductance of the heat pipes.

Project Results and Conclusions 

Several different flexible heat pipe constructions were tested. We varied the heat pipe's wick, water loading, plastic tubing, and end caps during testing. The main technical issues that we ran into were loading the heat pipes with the right amount of water, removing all air from the heat pipes, and getting a hermetic seal at the interface between the plastic tubing and metal end caps. We did get a measurable conductance in one of the heat pipe designs, but it was not large enough to beat already existing alternatives. More design iterations are required to further advance the technology.

We determined that the most promising material for the heat pipe housing is a trilaminate material that likely consists of fluorinated ethylene propylene (FEP) and nylon layers with an aluminum moisture barrier. FEP degrades very slowly in the low Earth orbit (LEO) environment based upon tests performed by  the Materials International Space Station Experiment (MISSE). Nylon provides greater structural integrity and is often used in retort food packaging. For optimal radiator optical properties, silver could be used within the material stack to provide high solar reflectivity and high infrared emission similar to second surface silver radiator tape. Uncoated glass fiber wicks were compared to a highly porous copper wicks, and the glass fiber wicks were found to be the best flexible wicking material.

The primary challenge was to iterate the design quickly. We were able to try six different heat pipe constructions. This was limited by the lead times for procurement and receiving. Some items took weeks or months for vendors to ship, but most of the lost time was due to waiting on procurement (caused by a reduction in the number of p-card holders and the overall procurement process that requires manual actions with several people in the loop on our side and the vendor side instead of typical instantaneous e-commerce transactions) and waiting on receiving to deliver the item to us. It would typically take around four weeks to get items that vendors already had in stock. The logistics around getting hardware for new design iterations was the limiting factor on the rate of improvement of the design.

This radiator design can reject more W/kg than currently available alternatives. It is particularly useful for high power density applications like Cubesats, Smallsats, high-throughput communication systems, space-based solar power, etc.

This is early/mid-stage (TRL 2) — 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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