Understanding the Refrigeration Systems on the International Space Station
Have you ever wondered why there is no refrigerator on the International Space Station (ISS)? While it may seem convenient to store food and samples, the space station has its own set of sophisticated refrigeration systems designed for specific purposes.
Why No Refrigerator in the Crew's Living Space?
The notion that astronauts leave food outside and watch out for space bears is a humorous exaggeration rather than an accurate depiction of life on the ISS. In reality, the design of crew meals on the ISS does not require refrigeration. Fresh milk and beer aren't readily available, and all main meals come pre-packaged, eliminating the need for a domestic refrigerator.
Refrigeration on the ISS: More Than Just Food
However, the ISS does have refrigeration systems for scientific experiments, storage of samples, and occasionally, the luxury of ice cream for the crew. There are several in-use refrigerators and freezers on the ISS designed for different purposes. Let's explore these systems in detail:
GLACIER: The General Laboratory Active Cryogenic ISS Experiment Refrigerator
GLACIER, the General Laboratory Active Cryogenic ISS Experiment Refrigerator, is a rear-breathing or water-cooled cryogenic freezer. This freezer is designed to preserve samples requiring extremely low temperatures, ranging from 4°C to -160°C. Samples can be stored and transported with significant precision, making it a crucial tool for scientific research in space.
Key Features:
Cooling via thermoelectric elements Operates with ISS water cooling or air cooling Temperature range: -20°C to -5°C (optional) Structural design for minimal crew interactionMELFI: The Minus Eighty-Degree Laboratory Freezer for ISS
MELFI, the Minus Eighty-Degree Laboratory Freezer for ISS, is a European-built experiment storage freezer designed for sample preservation. Using the Reverse Brayton Thermodynamic Cycle, MELFI can maintain temperatures from -95°C to 2°C, with the common operating temperatures of -95°C, -35°C, and 2°C. This freezer is equipped with four individually-controlled dewars, ensuring the precise storage of a wide range of scientific samples.
POLAR: The Cold Stowage Payload
POLAR is a Cold Stowage managed facility providing transport and storage of science samples at cryogenic temperatures. Designed to operate with power supplied to the EXPRESS Rack, this system can accommodate up to 12.75 liters of sample volume. It operates as an air-cooled payload in various vehicles, including the SpaceX Dragon and Orbital Cygnus capsules.
Astronaut Convenience and Scientific Expeditions
Astronauts have the opportunity to enjoy certain comforts, such as ice cream, thanks to refrigeration systems like the one found on the SpaceX Dragon cargo capsule. For instance, during preparations for a space mission, astronauts like Cady Coleman and Expedition 27 have demonstrated the use of GLACIER to insert samples. Also, ice cream was confirmed to be included in the SpaceX Dragon cargo during a pre-launch press conference, providing a minor perk during their long stay.
Conclusion
The International Space Station has its own specialized refrigeration systems that serve various purposes, from scientific research to ensuring the comfort of astronauts. These systems, including GLACIER, MELFI, and POLAR, are critical to the success of the ISS and the research conducted by the crew.