Prototype refrigerator for use in microgravity undergoes testing

One of the biggest challenges in long-term space exploration is a source of food for astronauts. While humans have been traveling in space since the 1960s, the way food is stored hasn't changed much. In particular, food is still typically freeze-dried, and there is no refrigerator to help things last.

A team of engineers from Purdue University, Air Squared Inc., and Whirlpool Corporation is at work on a prototype refrigerator that can operate in microgravity. The research could overcome a challenge that has faced engineers in getting a standard refrigerator to work in space, as well as it does on earth. Astronauts currently eat canned and dried food with a shelf life of about three years.

The research team, funded by the NASA Small Business Innovation Research program, wants to give astronauts a food supply that can last 5 to 6 years. The team has run a trio of experiments earlier this month to test aspects of the refrigerator design onboard a specially designed plane that flew in microgravity 30 times at 20-second intervals during four separate flights. The aircraft is Zero Gravity Corporation's weightless research lab, and it's the only test platform of its kind in the US.

Data analyzed from the experiments on the flights is supported by the NASA Flight Opportunities program, and the team has made two significant successes so far. Researchers found that their prototype refrigerator can operate just as well in microgravity as it does on the ground. Teams also determined that the prototype was no more likely to flood in microgravity than in normal gravity.

Any flooding could damage the refrigerator and food supply. Currently, the team is continuing to analyze data they've collected on test flights. Researcher Eckhard Groll says the team wants a refrigeration cycle that is resistant to zero gravity and works to standard specifications. The design of the refrigerator would cool food via a vapor-compression cycle similar to the process that standard refrigerators use on earth but without needing oil. An oil-free vapor-compression cycle eliminates any concerns of oil not flowing where it should in zero gravity. Data analysis on the project will be completed in the coming weeks.