An astronaut refrigerator, which allows residents of the International Space Station (ISS) to eat better, has been tested for microgravity.
Currently, astronauts are reliant on canned and dried food that have a shelf life of only about three years, but the new fridge could give astronauts a supply of food that could last five to six years.
A team of engineers from Purdue University, Air Squared, and Whirlpool Corporation has shown that a prototype they developed could potentially overcome the challenges of getting a traditional fridge to work in space just as well as it does on Earth.
The team ran three experiments earlier this month to test various aspects of the fridge design onboard a specially designed plane that flew in microgravity 30 times – for 20-second intervals – during each of four flights.
The aircraft, Zero Gravity Corporation’s (ZERO-G) unique weightless research lab, is the only test facility of its kind in the US.
From the data collected so far, it appears that the prototype can work just as well in microgravity as it does on the ground and will not flood (which could damage a refrigerator) in microgravity more than in normal gravity.
“We want a refrigeration cycle that can withstand gravity and operate to normal specifications,” said Professor Eckhard Groll of Purdue. “Our preliminary analysis clearly shows that our design allows gravity to have less influence on that cycle.
” Although refrigeration experiments have been tested in space before, they either didn’t work as well or eventually broke down.
The refrigerator design cools food through a vapor compression cycle, similar to the process used by a typical refrigerator on Earth, but without the need for oil.
Having an oil-free vapor compression cycle takes away the worry that oil won’t flow where it should without gravity.
The team’s prototype is about the size of a microwave, ideal for fitting into the ISS’s racking systems that store the payloads of research experiments.
Air Squared built the prototype and the oil-free compressor inside, which acts as the heart of the refrigerator.
The team’s experiments were designed to test a common hypothesis that pushing coolant through a vapor compression cycle at higher speeds would reduce the effects of gravity on refrigerator performance.
Prior to the test flights, it was shown that an oil-free vapor compression cycle can operate in different orientations – even upside down.
If a refrigerator can operate in any position, space crews don’t have to worry about whether the refrigerator is on a landing right side up.
“The fact that the refrigeration cycles operated continuously in microgravity during the tests with no apparent problems indicates that our design is a very good start,” said Purdue Ph.D. student Leon Brendel.
“Our first impression is that microgravity does not change the cycle in ways we were unaware of when we tested the effects of gravity on the design of the refrigerator on the floor by rotating and tilting it.”