Experimental zero-gravity fridge could finally allow astronauts to chill food

Modern, earthbound fridges aren’t designed to work in zero gravity or upside down.

But a team of engineers from Purdue University are building a fridge for zero gravity that operates in different orientations and just as effectively as the one in your kitchen, giving astronauts access to longer-lasting and more nutritious food.

Astronauts currently have limited diets: they can eat some fresh food, although it will spoil eventually, but much of their diet is composed of rehydrated, pre-packaged meals.

In addition, the food that astronauts currently eat during missions has a shelf life of only about three years – not enough for longer space missions. The new project aims to give astronauts a supply of food that could last five to six years.

Cooling systems currently on the International Space Station (ISS) are used for experiments and storing biological samples rather than for storing food, and they consume significantly more energy than fridges on Earth. The team is aiming to design a fridge that could be sent into space ahead of a mission and operate at freezer temperatures to meet the needs of astronauts.

The engineers are set to test possible solutions to making the type of cooling process that a typical fridge uses – vapour compression refrigeration – reliable enough for space missions.

Next month, their fridge design will be tested in a weightless research lab, the only testing space of its kind in the United States, that uses a specially designed plane to fly in microgravity dozens of times for 20-second intervals.

Data from these flights will help the team determine if the design is ready to be used in space.

The team’s fridge prototype is about the size of a microwave, ideal for potentially fitting onto the ISS and plugging into an electrical outlet like on Earth.

The researchers built two other experiments for use in the microgravity testing lab that will help them understand how well the prototype operates. One of these is a larger version of the prototype with sensors and other instruments to measure the effects of gravity on the vapour compression cycles, while the other experiment tests the prototype’s vulnerability to liquid flooding that could damage the fridge.

The Purdue team is testing the ability of the fridge design to operate in different orientations, such as upside down and sideways, by rotating the larger version of the prototype in the lab. Rotating this experiment gives the team a sense of how gravity affects the design before flying in May.

“Astronauts need to have better quality food that they can take along. And so that’s where a refrigerator comes into play. But it’s still a relatively novel technology for space,” said Purdue professor Eckhard Groll.

“During the last two years of this project, we have made tremendous strides in moving the technology forward.

“If these parabolic flights check out as we imagine they will and prove our system works in microgravity, we’re just a couple years away from having a refrigerator for spaceflight. We’re excited to provide the refrigerator for that flight. I think we have all the tools in place to do so.”

Leon Brendel, a Purdue student, said: “In a typical fridge, gravity helps to keep liquid and vapour where they are supposed to be. Similarly, the oil lubrication system inside of a fridge’s compressor is gravity-based. When bringing new technology into space, making the entire system reliable in zero gravity is key.”