Cryogenic Heat Pipe Temperature Control for Space Applications

Introduction to Cryogenic Space Applications

The ongoing development of space-based communications, sensors, and experiments, as well as the evolution of spacecraft electronics, are driving demand for tighter thermal control and more efficient heat removal in low temperature microgravity environments.

NASA’s goal was to develop reliable Refrigerator/Freezer (R/F) modules for future Life and Biomedical Sciences spaceflight projects. To do so, they sought to identify, develop, and demonstrate the complicated key Refrigerator/Freezer technologies required for these advanced R/F modules.

Traditional thermal management solutions such as air or liquid cooling are not viable options in space applications. Instead, Boyd developed passive, two phase cooling solutions specifically designed for cryogenic applications for NASA to test during space shuttle missions.

Problematic Refrigerator in the Spacelab Life Sciences on STS 40

The NASA Cryogenic Temperature Control Challenge

NASA was developing the Stirling Orbital Refrigerator/Freezer (SOR/F) experiment to prove out technologies that would enable reliable refrigeration during orbital projects. The subsystem candidates for the SOR/F were to be tested on Space Shuttle Discovery (STS 60).

The Boyd Solution for Cryogenic Temperature Control

As there is little to no atmosphere in space, dissipating heat into ambient air is not an option for effective thermal management solutions. Radiation is the most reliable cooling method in space, but internal components may not have access to radiation surfaces.

Boyd has pioneered the development of cryogenic heat pipes and loop heat pipes designed for use in microgravity environments. Engineers from Aavid have demonstrated a wide range of heat pipe/fluid systems for cryogenic thermal management, including helium at -270°C (3K), hydrogen at -250°C (23K), neon at -240°C (33K) and oxygen at -220°C (53K).

Boyd, known then as Thermacore, recommended that NASA use cryogenic heat pipes to transport heat on the SOR/F experiment. Boyd designed and fabricated copper and acetone heat pipe assemblies for NASA to test on the Space Shuttle Discovery.

The Results of the Stirling Orbital Refrigerator/Freezer Test

The acetone working fluid enabled the heat pipes to function in operating temperatures between -30°C (243K) and -60°C (213K) during Discovery’s STS-60 mission. The SOR/F heat pipes were proven capable of removing up to 10 W of power in the microgravity environment of space.

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