One of the main challenges of space travel has been food storage. While mankind has been sending people to space as early as 1961, there has never been any refrigerator to keep food cold and fresh during long missions.
Now, a new refrigerator prototype has been tested in microgravity environments. A collaborative effort between Purdue University, Air Squared Inc., and Whirlpool Corporation has demonstrated a feasible design that could potentially overcome the limitations of getting a conventional Earth-based refrigerator to work in the conditions of outer space.
IN SPACE: Seen in this undated ESA handout out photo European Space Agency (ESA) astronaut Andre Kuipers (R) and his NASA colleague Michael Foale eat Dutch cheese for breakfast on board the International Space Station.
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Keeping Food for Longer Space Missions
The canned and dehydrated (dried) food that astronauts eat in current space missions has a shelf life of about three years. With the new collaboration, supported by the Small Business Innovation Research (SBIR) program at NASA, food storage for future space missions could last from five to six years.
A news release from Purdue University shares that earlier this month, the team behind the upcoming refrigerator conducted three experiments, testing different aspects of the equipment's design. The refrigerator prototype was placed inside a special plane that flew in a simulated microgravity environment 30 times - with 20-second intervals - during each of its four flight attempts. The plane, a specially designed weightless research lab from the Zero Gravity Corporation - the only one of its kind in the United States.
Data gathered from the experiments, supported by the NASA Flight Opportunities program, shows two major advancements for the prototype. One is that the prototype refrigerator actually works just as well in a microgravity environment as it would otherwise do on earth. The other is that the prototype was no more likely to experience liquid flooding in microgravity than in Earth's gravity, especially since a liquid flood is hazardous to a fridge.
"We want to have a refrigeration cycle that is resistant to zero gravity and works to normal specifications," said Eckhard Groll, professor and head of the School of Mechanical Engineering at Purdue University, in the university news release. "Our preliminary analysis clearly shows that our design allows gravity to have less impact on that cycle."
A Promising Refrigerator for Space
The latest effort is not the first attempt to create a fridge intended for use in space missions. Earlier attempts included sending actual refrigerators on space, which eventually broke down or simply didn't work. One of the prior efforts toward improving food storage in space came from a team of engineers at the BioServe Space Technologies at the University of Colorado, Boulder. Dubbed the FRIDGE, or the Freezer Refrigerator Incubator Device for Galley and Experimentation, the units are just as large as a conventional microwave that works around common problems making Earth refrigerators unusable in space.
It has no rotating parts such as fans, and its heat is transferred along the International Space Station's cooling system. While the heat in conventional fridges is usually taken to the back and to the radiator, in space warm air does not rise up and dissipate. It tends to stay where it is, creating risks of overheating.
The same concepts apply in the latest Purdue University fridge, with the prototypes being about the same size as the UCB FRIDGE. Additionally, before the microgravity flight experiments, Purdue researchers showed that its oil-free vapor-compression cycle - which will be its cooling method - can operate well regardless of the orientation.
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