FRIDGE – The next generation freezer/refrigerator/incubator for food and experiment conditioning onboard the ISS

Abstract

The Freezer / Refrigerator / Incubator Device for Galley and Experimentation (FRIDGE) is a middeck locker-sized unit developed by BioServe Space Technologies for use within the Galley rack of the International Space Station (ISS) for food storage as well as in the EXPRESS rack for science experiment support. FRIDGE was optimized to provide a large Temperature Controlled Compartment (TCC) volume with the interior dimensions of 43.8 × 28.2 × 19.7 cm (17.25 × 11.10 × 7.75 in, DxWxH), which can be temperature-controlled from -20 to +48 °C. Temperature control of the TCC is accomplished using a total of four thermoelectric coolers (TECs) mounted to the top and bottom surfaces of the TCC. FRIDGE utilizes the ISS-provided Moderate Temperature Loop (MTL) as a thermal sink for the TECs and avionics. FRIDGE is based and improved on the Space Automated Bioproduct Lab (SABL) that has been in continuous operation onboard the ISS for over 5 years. Thermal improvements include the addition of vacuum panels into the insulation, optimized heat exchanger heat distribution and removal, improved door design, as well as the use of novel multistage bidirectional heat pumps (TECs). FRIDGE was designed without a single rotating part to minimize any maintenance work. This paper focuses on the thermal, mechanical, electrical, and software design of the payload compared to the initial test results from the verification testing. Thermal feedback control and safety monitoring is implemented using a suite of sensors that interface to an NI sbRIO-9636 data acquisition and control computer. Performance of the engineering unit was characterized to verify thermal models of operation, cooling/heating times, and robustness against uneven internal heat loads and off-nominal operation. After starting development at the end of 2018, the first two out of eight FRIDGE units were launched onboard NG-14 and commissioned onboard the ISS in the fall of 2020.This work was made possible by the National Aeronautics and Space Administration under grant REMIS-C2A-TO-003-GRF.