A shoe box standing in for an entire weight room.
Inside a capsule barely wider than a midsize sedan, four astronauts have been circling the Moon for ten days — and every one of them has been doing deadlifts.
NASA's Orion spacecraft, the vehicle at the center of the Artemis 2 mission, measures just 16.5 feet across and offers its crew a habitable volume of 330 cubic feet. That's roughly the interior of a large walk-in closet, shared among four people for a week and a half. The engineers who designed the mission knew that keeping the crew physically intact inside that space would require some creative thinking.
What they came up with looks, at first glance, like a handle stolen from a cable machine at your local gym. Attached to a compact flywheel, the device lets astronauts strap their feet on either side and pull — but that description barely scratches the surface of what it can do. The whole unit is not much bigger than a large shoe box. The flywheel itself weighs 30 pounds. And yet it can simulate resistance up to 400 pounds, covering everything from low-resistance cardiovascular rowing to squats, deadlifts, bicep curls, and high pulls.
Canadian Space Agency astronaut Jeremy Hansen demonstrated the machine's range in a video released before the mission. A slow rowing pace at light resistance becomes a cardio session; crank up the flywheel's dynamics and you're doing strength work. The protocol NASA settled on calls for each crew member to spend 30 minutes a day on the device, positioning their body into the open center of the cabin to make the most of the limited room.
Video captured two days into the Artemis 2 mission shows NASA astronaut Victor Glover working through his daily session while Hansen, a few feet away, prepares lunch. It is an oddly domestic scene for a spacecraft looping around the Moon.
The reason this matters goes well beyond comfort. Exercise physiologist Jessica Scott, who works at Memorial Sloan Kettering Cancer Center and contributed to early versions of the flywheel device for NASA, put it plainly to NPR: ten days in space without physical activity is roughly equivalent to ten days of complete bed rest. The body, deprived of the constant low-level resistance that gravity provides on Earth, begins shedding muscle mass and bone density with alarming speed. "You would feel very weak, and your muscles start to lose size very quickly," Scott said.
In controlled bed-rest studies — experiments where participants lie still for days at a time to simulate microgravity's effects — Scott's team found that introducing a flywheel-based exercise routine made a decisive difference. "What was really exciting," she told NPR, "was that the small device could prevent the declines, the same amount that a full gym could do." A shoe box standing in for an entire weight room.
The astronauts arrived at the mission already in serious shape. A photo NASA shared from last summer shows mission specialist Christina Koch training on Earth ahead of the flight, and the image drew its own attention online — one social media user responded with something close to reverence at her visible conditioning. Koch's preparation apparently extends well beyond the gym: she surfs, rock climbs, ice climbs, does triathlons, practices yoga, and goes backpacking.
Orion is expected to splash down in the Pacific Ocean today, bringing the crew home after their ten days aloft. The flywheel experiment will be scrutinized as NASA looks toward longer missions — eventually to Mars, where the transit time alone could stretch to seven months each way. If a device the size of a shoe box can hold muscle loss at bay for a lunar trip, the question becomes whether it can do the same across the vast distances that lie further out.
Notable Quotes
The small device could prevent the declines — the same amount that a full gym could do.— Jessica Scott, exercise physiologist, Memorial Sloan Kettering Cancer Center
We can change the dynamics of this device so that we can do weightlifting with it — squats, deadlifts, curls, high pulls.— Jeremy Hansen, Canadian Space Agency astronaut, Artemis 2 crew member
The Hearth Conversation Another angle on the story
Why does it matter so much that they exercise? Ten days doesn't sound that long.
In microgravity, the body starts breaking down almost immediately. Without gravity pushing back against every movement, muscles have nothing to resist, and they shrink fast. Bone density follows.
How fast are we talking?
An exercise physiologist who worked on the device compared ten days in space without exercise to ten days of complete bed rest on Earth. You'd come home noticeably weaker.
And this flywheel thing actually solves that?
In bed-rest studies designed to mimic the effect, it matched what a full gym could do. That's the remarkable part — the size of the solution versus the size of the problem.
What does 330 cubic feet actually feel like?
Think of a large walk-in closet. Four people, ten days, all their equipment. The astronaut using the machine has to position their body into the open center of the cabin just to have room to pull.
So the design had to account for the cramped space from the start?
Completely. The flywheel weighs 30 pounds and fits in something the size of a large shoe box. Every pound and every inch was a constraint the engineers had to solve around.
Is this just about the Moon trip, or does it point somewhere further?
That's the real question. A lunar mission is ten days. A Mars transit is closer to seven months each way. If the flywheel works here, it becomes a serious candidate for keeping crews functional across much longer distances.
What happens if they don't solve it for Mars?
You'd arrive at another planet with a crew too weakened to do the work they went there to do. The exercise problem isn't a comfort issue — it's a mission-critical one.