Thermal Testing of an AMDROHP (Additively Manufactured Deployable Radiator Oscillating Heat Pipes) for Use in High-Powered CubeSats

Abstract High-power small satellites will play an important role in reducing the cost of space missions. High power levels are required to satisfy high bandwidth communication needs, as well as to accommodate other critical systems such as propulsion and high-power electronics. One of the current high-power limitations is the need to overcome the thermal challenges associated with high thermal loads. While substantial work has been done in the development of deployable solar arrays, relatively little attention has been given to small satellite deployable radiators. Previous deployable small satellite radiators rely on a mechanical hinge to conduct heat from spacecraft to radiator. However, this presents a thermal choke point and limits heat flow. Thus, a deployable radiator design concept is currently being explored as a thermal solution for high powered electronics in CubeSats. This Additively Manufactured Deployable Radiator Oscillating Heat Pipes (AMDROHP) design concept combines the function of a deployable radiator with high performance Oscillating Heat Pipes in this compact thermal solution. In this project, significant efforts have gone into developing the mechanical, deployable aspect of this design while maximizing its thermal performance, and this joint development has been discussed in previous publication. This initial design was additively manufactured and thermally tested at the Jet Propulsion Laboratory. The results of the thermal testing of the initial AMDROHP design are discussed and presented in this work. The device is tested across a range of heat inputs under “micro-gravity” and “gravity-assisted” orientations for the working fluids R134a and Ammonia. The performance and behavior of the AMDROHP device are characterized by transient temperature measurement data under these different conditions. The results were interpreted to determine the feasibility of the design. Although AMDROHP did operate under “gravity-assisted” orientation, it did not start-up under “micro-gravity” orientation. Furthermore, the range of operation under “gravity-assisted” orientation was less than expected. Based on these results, possible design changes have been identified to improve AMDROHP performance under space-like conditions. These changes include creating a shorter adiabatic length by decreasing the path length of the helical joint, as well as increasing the inner channel diameter. These changes will allow for better thermal performance and to better avoid any imperfections in the additive manufacturing process to cause negative effects on OHP operation. In this study, experimental testing provided actionable information about the initial design of AMDROHP to lead to design improvements. These design improvements will be implemented in the next design iteration of AMDROHP.