Getting a spacecraft to Mars or beyond requires an enormous amount of fuel, most of which has to be hauled from Earth, adding to the overall cost and weight of the spacecraft. NASA has been working on a different approach, one that could be more efficient and effective.

It wants to refuel a spacecraft in orbit before heading out for the mission. What’s even more interesting is that the space agency just finished testing a component that could make that possible: a cryocoupler.

So what exactly is a cryocoupler, and why does it matter?
Think of it as the nozzle of a gas pump, except for a spacecraft. A cryocoupler allows a rocket or deep-space probe to dock with an orbiting fuel station, refueling it with cryogenic propellants such as liquid hydrogen and liquid oxygen before pushing the craft into the depths of the solar system.

The cryocoupler has been developed by American defense and technology company L3Harris. The team at NASA’s Marshall Space Flight Center in Huntsville, Alabama, tested it by running liquid nitrogen through the coupler at -321 degrees Fahrenheit, analyzing its performance at extremely cold temperatures in both connected and disconnected configurations.

Does this mean in-orbit refueling is almost here?
Unfortunately, not yet. As cryocoupler project manager Travis Belcher puts it, “in-orbit cryogenic refueling between two spacecraft has yet to be done and remains one of the toughest engineering challenges in spaceflight.”

The encouraging part, however, is that this coupler is fully automated with no spacewalk needed. Furthermore, it can attach and detach multiple times.

Even so, these are early-stage tests, and future evaluations will be tailored to specific conditions and missions. If the engineering holds, spacecraft could one day top up in orbit rather than carrying all the possible fuel from the ground.