Development of a Deployable Radiator Equipped with Loop Heat Pipes for High Throughput Communication Satellites

High heat-rejecting technology becomes increasingly necessary as communication capacity grows for the next generation of geostationary communication satellites. Engineering Test Satellite-9 (ETS-9), to be launched in fiscal 2025 or later, is being developed by the Japan Aerospace Exploration Agency (JAXA) to demonstrate its innovative bus technology for high- throughput communication satellites. The main technologies to be newly developed for the ETS-9 are high electrical power supplies, electric propulsion, and high heat rejecting technology. Although it is not installed on the ETS-9 flight model, we have developed a deployable radiator (DPR) equipped with loop heat pipes (LHPs) that have completed qualification testing (QT). Since the DPR is equipped with a flexible heat transport device using an LHP, the DPR can unfold 180o after launch to dissipate heat efficiently into space. QT included a deployment test and performance evaluation of its heat-rejecting capacity. In addition to the qualification tests, we conducted long-term operation tests using a breadboard model (BBM) and tests in the microgravity environment of the International Space Station (ISS), confirming the design’s high reliability. The long-term operation test using the LHP BBM determined that no non-condensable gas (NCG) was generated after high-temperature operation for seven years, from the end of May 2017 to the end of February 2025. This paper describes the results of the DPR qualification test, an overview of the in-orbit pre- demonstration of LHP, and an overview of the long-term operational test using LHP BBM.