Purdue University researchers Eckhard Groll, left, and Leon Brendel stand next to a fridge experiment they designed to work in different orientations and even upside down.

Float on: Creating a more energy-efficient refrigerator that works in space

Refrigerators would help astronauts on long missions, such as going to the moon or Mars, to maintain access to nutritious, longer-lasting food. But modern household refrigerators don’t work in zero gravity where they might be upside down or in a variety of different orientations. A research team with members from Purdue University in Indiana; Benton Harbor, Michigan-based Whirlpool Corporation; and Broomfield, Colorado-based Air Squared are working to create a new refrigerator that will work in space.

The problems

During their missions, astronauts currently rely on canned and dried food with a shelf life of about three years. This project, funded by NASA, aims to give astronauts a food supply that is better quality and will last five to six years to support longer missions. 

But refrigerators are still an uncommon technology in space. Gravity helps to keep liquid and vapor where they need to be inside the units, and the compressor’s oil lubrication system also is gravity-based. Previous space fridges operating in zero gravity have not worked well or have broken down. 

Due to these conditions, the International Space Station’s current cooling systems are used for storing scientific experiments and biological samples instead of food. The devices consume far more energy than refrigerators on Earth. 

The fix

The researchers are working on cooling solutions that work in space but use similar technology to a household unit: vapor compression refrigeration. The new space fridge won’t be more energy-efficient than household models, but it will be more energy-efficient than previous space fridge designs. The estimated efficiency gains are still confidential right now, the researchers told Centered.

“Current space fridges operate with different technologies than our fridges at home,” said Purdue researcher Leon Brendel. “A famous example is MELFI which is a successful space cooler but its cooling technology is the Reversed Brayton cycle which is inherently less efficient for food storage temperatures than the vapor compression cycle we use. So, we are more efficient by using a whole different technology than current space coolers.” 

This fridge will use an oil-free compressor to avoid problems with oil flow in zero gravity. The team is also working to make the unit extra reliable because refrigerator repair people aren’t exactly readily available in space.

The prototype is about the size of a microwave and will plug into an electrical outlet just like household versions. A larger version is equipped with sensors and other technologies to measure the effects of gravity on the unit’s vapor compression cycles. Another experiment will test the vulnerability to liquid flooding that could damage the fridge.

What’s next

The team will test their new refrigerator in May at Zero Gravity Corporation’s weightless research lab that creates microgravity, the only testing facility of its kind in the country. Data gathered from the test flights will help the researchers figure out if their fridge is ready for use in space.

If the tests work well, astronauts could have a refrigerator like this on spaceflights in a couple of years.

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