Engineering testing of the capillary pumped loop thermal control system for the NASA EOS-AM spacecraft

This paper describes the design and testing of the Engineering Development Model (EDM-2) for the Capillary Pumped Heat Transport Systems (CPHTS) which will be used on the NASA Earth Observing System (EOS-AM) Spacecraft for sensor instrument heat acquisition, transport, and rejection. EDM-2 testing was performed in ambient and thermal-vacuum conditions to verify the operation of the EOS-AM CPHTS design. During ambient testing the EDM-2 was configured in a horizontal orientation in order to most closely simulate 0-g conditions on Earth. All EDM-2 ambient tests were successful. Both loops 1 and 2 successfully started on the first attempts. Additionally, both have successfully undergone reservoir temperature change transient testing and five orbit simulations of instrument operation. EDM-2 was tested in a thermal-vacuum chamber in horizontal and reflux configurations. Both loops successfully operated in a horizontal orientation simulating 0-g operation despite problems with the Heater Control Electronics-3A (HCE-3A) used to maintain the reservoir setpoint temperature. One loop of EDM-2 was successfully tested in a reflux orientation to simulate operation during spacecraft thermal-vacuum testing. However, because of problems with the KCE-3A, the reservoir setpoint had to be controlled using the “on-off” heater controller supplied by the experiment´s control software. In summary, both EDM-2 CPHTS loops operated well during thermal-vacuum testing in horizontal and reflux orientations