Regular supply launches keep astronauts aboard the ISS supplied with relatively fresh food, but a flight to Mars won't get deliveries. If we're going to visit other planets, we'll need a fridge that doesn't break down in space — and Purdue University researchers are hard at work testing one.
You may think there's nothing to prevent a regular refrigerator from working in space. It sucks heat out and puts cold air in. Simple, right? But refrigerators rely on gravity to distribute oil through the compressor system that regulates temperature, so in space these systems don't work or break down quickly.
The solution being pursued by Purdue team and partner manufacturer Air Squared is an oil-free version of the traditional fridge that will work regardless of gravity's direction or magnitude. It was funded by NASA's SBIR program, which awards money to promising small businesses and experiments in order to inch them toward mission readiness. (The program is currently on its Phase II extended period award.)
In development for two years, the team at last assembled a flight-ready prototype, and last month was finally able to test it in microgravity simulated in a parabolic plane flight.
Initial results are promising: The fridge worked.
"The fact that the refrigeration cycles operated continuously in microgravity during the tests without any apparent problems indicates that our design is a very good start," said Leon Brendel, a Ph.D. student on the team. "Our first impression is that microgravity does not alter the cycle in ways that we were not aware of."
Short-term microgravity (the prototype was only weightless for 20 seconds at a time) is just a limited test, of course, and it already helped shake out an issue with the device that they're working on. But the next test might be a longer-term installation aboard the ISS, the denizens of which would no doubt like to have a working fridge.
While the prospect of cold drinks and frozen (but not freeze-dried) meals is tantalizing, a normal refrigerator could be used for all kinds of scientific work as well. Experiments that need cold environments currently either use complicated, small scale cooling mechanisms or utilize the near-absolute-zero conditions of space. So it's no surprise NASA got them aboard the microgravity simulator as part of the Flight Opportunities program.
Analysis of the data collected on the flights is ongoing, but the success of this first big test validates both the approach and execution of the space fridge. Next up is figuring out how it might work in the limited space and continuous microgravity of the ISS.