Hughes hitchhikes on Shuttle to test satellite thermal system

Citation

(1998), "Hughes hitchhikes on Shuttle to test satellite thermal system", Aircraft Engineering and Aerospace Technology, Vol. 70 No. 5. https://doi.org/10.1108/aeat.1998.12770eaf.001

Hughes hitchhikes on Shuttle to test satellite thermal system

Hughes hitchhikes on Shuttle to test satellite thermal system

Keywords Aerospace, Heat pipe, Heat transfer, Hughes, Satellite

November 1997's space shuttle mission included a test of a high-efficiency temperature control system similar to that on a new satellite being built by Hughes Space and Communications Company.

The test provided additional zero-gravity performance data on a loop heat pipe design being used on Hughes' powerhouse HS 702 satellite. When the first space-craft in the series flies this year, loop heat pipes will be attached to deployable radiator panels to dissipate heat generated by the high-power satellite's electronics.

"We have flight data from similar Russian systems and we have done considerable testing on the ground, so we are confident of the loop heat pipe design. We did the best we could to simulate zero-gravity on earth, and this test will give us more data about the system's performance in real conditions", said Hughes's project manager, Bruce Drolen.

The compact heat pipe payload travelled as a "hitchhiker" on the space shuttle Columbia, which began its 15-day mission on 19 November 1997. The "hitchhiker" category is for small payload packages carried in the Shuttle cargo bay. Dynatherm Corporation, which builds the heat pipes, developed the flight experiment and leads the test team. Hughes, which will put the technology to its first commercial use, is a major partner. Other teammates are NLR, a research laboratory in The Netherlands, Center for Space Power at Texas A&M, Naval Research Laboratories, Wright-Patterson Air Force Base, Air Force Phillips Laboratory, NASA's Goddard Space Flight Center and The Aerospace Corporation.

A heat pipe is a metal tube in which a fluid alternately evaporates and condenses, transferring heat from one region of the tube to another. They are used in satellites to transfer the heat generated by on-board electronic equipment to radiator panels that dissipate the heat into space.

In previous heat pipe designs, the heat is transported along the length of the tube as the liquid vapourises and condenses in the same tube. A loop heat pipe system can be compared to a car's cooling system. The vapourised liquid, in this case ammonia, moves through a transport line to a condenser, or a series of coils similar to a car's radiator. The liquid cools and condenses and flows through another line back to the starting point. By keeping the vapour and the cooled liquid separate, the loop heat pipe can carry more heat for greater distances than other pipes. The "pump" that moves the fluid around the loop is a cylindrical porous wick with extremely small pores that is located at the heat input portion of the loop. The small pores act as both a capillary pump and an effective separator between the vapour and liquid phases.

The HS 702 series is designed to be the most powerful, largest-capacity communications satellite line to date, generating between 11 and 20 kilowatts and carrying electronics payloads of up to 1,000 kilograms. To dissipate the heat from such a high-powered system, Hughes engineers realised they needed larger radiator panels and more efficient heat pipes. For the HS 702, one loop heat pipe system uses more than 50ft of tubing. Most of the tubing forms the coils of the condenser, which is built into deployable extensions of the radiator panels. One loop heat pipe takes the place of about ten traditional heat pipes.

For further details contact Hughes Space and Communications Company. Tel. +44 (1) 310 3646363.