Asets-Ii Oscillating Heat Pipe Space Flight Experiment: The First Six Months on Orbit

Abstract

On September 7th, 2017 the U.S. Air Force Research Laboratory launched the second Advanced Structurally Embedded Thermal Spreader (ASETS-II) flight experiment to space on Orbital Test Vehicle 5. The ASETS-II experiment is made of three low-mass, low-cost oscillating heat pipes (OHPs) and an electronics/experiment control box. The three primary science objectives of the experiment are to measure the initial on-orbit thermal performance, to measure long duration thermal performance, and to assess any lifetime degradation. The three OHPs on ASETS-II are of varying configuration (center heating with single-and double-sided cooling) and working fluids (butane and R-134a) in order to isolate specific performance parameters of interest. OHP #3 was specifically designed in order to explore the operating limits on OHP operation in microgravity without requiring excessive operating temperature or pressure. Data collected during the first 6 months of on-orbit operations are presented in this paper. It is shown that each OHP performed as expected, where on-orbit data for OHPs #1 and #2 mirrored ground-truth performance, and the OHP #3 on-orbit maximum operating evaporator temperature increased from ground-truth. The OHPs experienced no significant hysteresis effects and OHP #1 performed successfully in six-week long continuous operation.

A pulsating heat pipe embedded radiator: Thermal-vacuum characterisation in the pre-cryogenic temperature range for space applications

“…The tests have all been conducted in horizontal orientation because for a planar capillary device on ground this is the closest condition to the microgravity [20].…”

“…For space applications, the ability to achieve low equivalent thermal resistance without the assistance of gravity nor the presence of a porous wick to help the return of the condensate attracted the attention of many research groups. The PHP characterization in space environment has just begun in the last few years, supported by research programmes also from space agencies and scientific research organisations, like the ESA Microgravity Application Programme, which funded the project on Innovative wickless heat pipes for ground and space applications (INWIP) [17] [18] [19], the two on-orbit technology demonstrators from U.S. Air Force Research Laboratory STP-H4-ATT [20] and JAXA SDS-4 [21], with the aim of increasing the TRL of the technology. Due to the complexity of experimental research in space, the two demonstrators could prove their long-term reliable operation with a single set of parameters, but a thorough thermal characterization was intrinsically not possible.…”

Low-Order Model of the Dynamics and Start-Up of a Pulsating Heat Pipe

“…In the literature on PHPs, two foci have developed: On the one hand, there are many papers that investigate the performance of PHPs experimentally (Quan and Jia, 2009;Ma et al, 2008;Song and Xu, 2009;Qu et al, 2009;Khandekar et al, 2003;Singh et al, 2021), often with the goal to correlate performance with design and operational parameters, such as tube diameter, filling ratio, and orientation with respect to the field of gravity. Also note recent experimental investigations on PHP operation in micro-gravity by Taft and Irick (2019). More recently, performance improvements were achieved by deviating from the classical structure of a PHP and introducing e.g.…”

Research and Development of Loop Heat Pipe – A Review

“…It can transmit a large amount of heat through a small cross-sectional area for long distances without external power, which is recognized as one of the most effective passive heat transfer technologies and is widely used in the field of electronic cooling (Singh et al 2019;Mirmanto et al 2018;Faghri. 2012;Li et al 2016;Krishna et al 2017) and energy recovery (Srimuang et al 2012;Yodrak et al 2011) and space flight (Brenton et al 2019). Gaugler (1944) and Grover et al (1964) pointed out that the thermal conductivity of heat pipe is far more than any other metal materials.…”