Final Publication Released on the Second Advanced Structurally Embedded Thermal Spreader (ASETS-II) Experiment
The final publication for the ASETS-II experiment has been published, Advanced Structurally Embedded Thermal Spreader Oscillating Heat Pipe: Postflight Hardware Analysis.
The paper found that the oscillating heat pipes (OHPs), also called pulsating heat pipes (PHPs), in the ASETS-II experiment did not experience physical degradation to the fluid nor structure.
This lack of degradation over the 780 days of on-orbit operation shows that OHPs are viable heat transfer devices for on-orbit applications.
Overview of the Experiment
The second Advanced Structurally Embedded Thermal Spreader Oscillating Heat Pipe (ASETS-II) experiment was developed by the Air Force Research Laboratory (AFRL) to evaluate oscillating heat pipes (OHPs), also called pulsating heat pipes (PHPs), in a long-duration on-orbit environment. The experiment set out to determine OHP functionality, characterize their behavior, and explore the predicted limits of operation in a microgravity environment. The resulting thermal data and physical analysis of the hardware was published in 6 journal and conference papers and the thermal data was released on the NASA PSI website for 3rd party analysis.
ThermAvant developed and delivered 10 OHPs to AFRL for the experiment. Starting in 2016, six of the OHPs were tested on ground to establish a performance baseline. The results and analysis of these prelaunch ground truth tests was published by Taft and Smith [1]. On September 7, 2017, AFRL launched three of these OHPs on board the X-37B Orbital Test Vehicle 5 (OTV-5) for a 780-day mission, landing on October 27, 2019. The other three OHPs remained on-ground. The first 6 months on orbit were published by Taft and Irick [2] and the thermal results of the complete 2-year mission were published by Drolen et al. [3]. Drolen et al. found that the thermal performance was constant throughout the entire experiment and that the performance was predictable via on-ground testing and modeling. This demonstrated the viability of the OHP as a heat transfer device in satellites. The thermal data from this experiment was released on the NASA Physical Sciences Informatics website for 3rd party analysis and model development [4-5].
After the X-37B landed, the on-orbit and on-ground hardware was evaluated for physical changes over the course of the experiment to the fluid and the structure. No degradation was found. The results of this analysis are in this final ASETS-II paper published on December 2 [6]. This experiment and the series of publications demonstrate the viability of OHPs for long-term satellite applications.
References
1. Taft, B. S., and Smith, S. M., “ASETS-II Oscillating Heat Pipe Space Flight Experiment: Ground Truth Results,” ASME 2017 Heat Transfer Summer Conference, Bellevue, Washington, D. C., July 2017, Paper HT2017-4706.
2. Taft, B., and Irick, K., “ASETS-II Oscillating Heat Pipe Space Flight Experiment: The First Six Months on Orbit,” Frontiers in Heat and Mass Transfer (FHMT), Vol. 12, No. 1, 2019, pp. 1–7. https://doi.org/10.5098/hmt.12.24
3. Drolen, B. L., Wilson, C. A., Taft, B. S., Allison, J., and Irick, K. W., “Advanced Structurally Embedded Thermal Spreader Oscillating Heat Pipe Micro-Gravity Flight Experiment,” Journal of Thermophysics and Heat Transfer, Vol. 36, No. 2, 2022, pp. 314–327. https://doi.org/10.2514/1.T6363
4. Wilson, C. A., Drolen, B., Taft, B., and Allison, J., “Advanced Structurally Embedded Thermal Spreader II (ASETS-II) Oscillating Heat Pipe Flight Experiment and Database,” Joint 21st International Heat Pipe Conference and 15th International Heat Pipe Symposium, Melbourne, Australia, Feb. 2023, Paper 3.
5. Allison, Jonathan & Taft, Brent. “Advanced Structurally Embedded Thermal Spreader II (ASETS-II) Oscillating Heat Pipes (OHP).” NASA Physical Sciences Informatics (PSI). https://psi.ndc.nasa.gov/app/record/164634
6. Wilson, C. A., Miller, A., Drolen, B., Taft, B., and Allison, J., 2024, “Advanced Structurally Embedded Thermal Spreader Oscillating Heat Pipe: Postflight Hardware Analysis,” Journal of Thermophysics and Heat Transfer, 0(0), pp. 1–7. https://doi.org/10.2514/1.T6983.