Copper - Ammonia Heat Pipes for Small Satellites (Cu-NH3 HPs for Space)

A new product, copper-ammonia Heat Pipe (HP), will be developed and characterized for space applications. The main objectives are:

1. Produce first in the world copper-ammonia HP.
2. Demonstrate superior performance in the temperature range from -60℃ to +60℃. This temperature range covers most of Small Satellite applications as well as many others.
3. Obtain life test data to demonstrate HP reliability for space applications.

The proposed technology will provide a product with new capabilities:

1. HP operation in any orientation during ground testing.
2. Freeze tolerance.
3. Miniaturization (minimum diameter reduction by >50%).
4. High heat flux capability (>50 W/cm²).

• This will be the first HP that can survive ammonia freezing! It will be a great value to Goddard’s lunar programs and other missions where component temperature could drop below ammonia freezing point (-78°C).

• The ability to operate with higher tilts during ground testing will overcome orientation issues during instrument and observatory testing. This allows optical instruments to be ground tested without limitations associated with axial grooved HPs.

• The reduction of the heat pipe diameter will be achieved. The smaller diameter HPs are well suited for CubeSats. That could potentially be groundbreaking for thermal management within CubeSats.

• Also, the small diameter ammonia HPs (<4 mm) will be able to replace thermal straps in some next generation thermal systems. Small diameter copper-ammonia HP will be more flexible than copper straps. As a result, the amount of force applied to optical sensors and other electronics will be reduced (i.e., better mechanical isolation).

• The test results will be utilized to expand the existing HP models. The results will be presented to the thermal space community to enhance Goddard’s reputation.

• The effective thermal conductivity of copper-ammonia HP will be at least an order of magnitude higher than the Annealed Pyrolytic Graphite (APG is the most conductive solid material used for space applications). The copper-ammonia HP approach offers a compact passive heat transfer and reduced weight in comparison with APG, copper or aluminum thermal straps.

The short-term Return on Investment (RoI) will be realized from lunar programs and savings during ground testing. The proposed technology could save tens of thousands of dollars spent on one system that employs freeze protection of ammonia HPs. The cost of cold plates used in ground testing to overcome inability of conventional ammonia HPs to operate against gravity ranges from hundreds of dollars to several thousands of dollars. The labor associated with installation and removal of these cold plates often reaches additional thousands of dollars. The proposed HPs could reduce complexity and eliminate these expenses due to their ability to operate in any orientation in 1-g environment. The long term RoI is anticipated as well since thermal challenges are not always apparent during the design phase of the program. As a result, thermal loads could become an issue during the testing phase. The proposed copper-ammonia HP will allow us to resolve thermal problems with minimal design impact. The return from one situation of this type could be substantially higher than the investment into the proposed effort.

This is early/mid-stage (TRL 3) — 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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