How Do Astronauts Stay Attached During a Spacewalk (and Not Float Away)?
How Do Astronauts Stay Attached During a Spacewalk (and Not Float Away)?
Not many people know the name Bruce McCandless II. Almost everyone has seen his photograph: an astronaut adrift against the black, no line running back to the shuttle, nothing holding him to anything at all. In February 1984, McCandless became the first human being to fly free in space, riding a jet-powered backpack instead of a rope.
I was eight when I found that photograph in a magazine. It scared me. A single person, that far from anything, swallowed by that much dark. It did something else too: it planted a want in me, vague and enormous, for whatever it was that let a person go out there and still come back.
Bruce McCandless II performing a free-flying spacewalk far from the Space Shuttle with Earth visible below.
The Photo Everyone Remembers, and No One Repeats
That photograph is where most people's idea of a spacewalk still lives: a figure floating loose, with nothing but distance around him. McCandless flew it for real on February 7, 1984, testing NASA's Manned Maneuvering Unit a few hundred feet out from the shuttle Challenger. Robert Stewart took a turn as well, across that mission's two untethered spacewalks. The picture captures one moment. The practice behind it lasted less than a year.
The Manned Maneuvering Unit flew three shuttle missions, all of them in 1984. Its last operational use came that November, when spacewalkers flying the packs retrieved two stranded communications satellites on STS-51A. Then NASA retired it.
Routine spacewalks on the shuttle and at the International Space Station have used safety tethers ever since. There has been one deliberate exception, and it only underlines the point: in September 1994, Mark Lee and Carl Meade made the first untethered U.S. spacewalk in a decade to test SAFER, a small backpack designed not to fly anywhere but to bring a detached astronaut back. Spacewalkers still wear one today.
This is how the work goes now: clipped in from start to finish, moving hand over hand or riding the station's robotic arm, working down a tightly scheduled list of repair tasks while mission control listens over the radio. Free flight isn't part of the job anymore.
What strikes me isn't just that McCandless flew free. It's that two astronauts operated the MMU on that one mission, and NASA still stopped flying it inside the same year. Which leaves a plainer question: what physically holds a person to a moving space station while both hands are busy?
Two astronauts repairing the Canadarm2 robotic arm outside the International Space Station.
The Answer Is a Tether, a Foot Restraint, and a Robotic Arm
The question stopped being theoretical on one morning in June 2026.
On June 30, NASA astronauts Chris Williams and Jessica Meir began a spacewalk at 8:20 a.m. Eastern time to replace a broken wrist joint on Canadarm2, which had malfunctioned on May 27 during normal operation. Neither of them drifted anywhere to get there.
The answer is almost anticlimactic. A safety tether keeps each astronaut attached to the station, and handrails carry them from one worksite to the next. For heavier jobs they lock their boots into a foot restraint, or ride Canadarm2 itself — the roughly 58-foot, seven-jointed arm that NASA notes can hold a spacewalker in place with both hands left free.
Restraint isn't a convenience out there. It's Newton's third law made practical: push on a stuck bolt with nothing to brace against, and the astronaut is what moves — rotating, drifting, or both — while the bolt stays put.
Anchoring the body turns out to be the easy part. Keeping the person inside it alive is a separate problem, and the tether has nothing to do with that one.
Astronaut conducting underwater EVA training in the Neutral Buoyancy Laboratory with safety divers nearby.
The Suit Is Doing More Work Than the Person Inside It
NASA's own spacesuit reference calls the suit a personal environment rather than a piece of clothing: a system meant to hold pressure, breathable oxygen, cooling, carbon dioxide removal, humidity control, and communications around one human body, in a vacuum that supplies none of it.
NASA's descriptions keep landing on one comparison — closer to a one-person spacecraft than to anything you would wear. That framing changed how I read the rest of the list. Nearly all of those functions live in a single place, the backpack, officially the Portable Life Support System and broadly described in NASA's EVA systems reference. None of it comes free. The pattern is the one every diver and mountaineer eventually meets: the equipment that keeps a hostile environment survivable also sets a limit on how long anyone can stay in it.
Outside the station, almost nothing about orientation is intuitive. Astronauts work from rehearsed procedures, suit displays, and constant radio contact with the ground to know where they are and what comes next. What none of that answers is the simplest question of all: how long does any of it last?
Shorter than it sounds, and closer to the numbers divers work with than to anything astronauts usually get credit for. NASA doesn't measure a spacewalk in miles. Its practical limits are time and supply — life-support consumables loaded in fixed amounts before the hatch ever closes. Difficult places on Earth work much the same way: reach depends less on distance than on how long people and equipment can stay safe, which is exactly what limits human exploration of the ocean as well.
Astronaut using a foot restraint and safety tether while performing maintenance outside the International Space Station.
The Clock No One Talks About
A planned ISS spacewalk generally runs several hours. The June 2026 Canadarm2 repair lasted seven hours and twenty minutes, according to NASA's mission report. Every life-support function has to keep running for all of it, drawing down a supply that can't be topped up. There is a backup, the Secondary Oxygen Pack, but it exists purely for emergencies — an open-loop purge system built to deliver at least thirty minutes of pressure-regulated oxygen if the main life-support system fails or runs out.
NASA's 2025 spacesuit standard requires an EVA suit to provide drinking water on demand at a minimum rate of 240 milliliters per hour. That's a design requirement, not a record of what anyone actually drinks.
Taken together, the numbers describe a job with an expiration date built in. McCandless flew under the same kind of clock; what he had that today's spacewalkers don't is permission to leave the structure. That, to me, is the real difference between his flight and the Canadarm2 repair — not skill, but what gets signed off. The harder trick is getting comfortable enough with the clock to finish the work before it runs out.
The Same Pool Trains Astronauts and Offshore Energy Workers
Every major spacewalk task gets rehearsed underwater long before it happens in orbit, alongside virtual reality and other simulators. The Neutral Buoyancy Laboratory near Houston holds a full-scale mockup of much of the station's exterior, submerged in a tank deep enough to let a suited person and their tools hang neutral, moving roughly the way they would in freefall. Two trainees can run a lunar-surface spacewalk scenario there for up to six and a half hours, with safety divers and camera crews working alongside them throughout.
In 2023, NASA agreed to let the company that operates the facility open it to a different kind of trainee: offshore oil and gas workers learning survival skills for jobs over open water. Astronaut training never stopped running there. How much of the curriculum crosses over between the two groups isn't spelled out in NASA's announcement. What is confirmed is that one tank now serves both kinds of dangerous work.
Jessica Meir trained there before a run of 2026 spacewalks that shows the shape of the job. The Canadarm2 repair came in June. On August 6, she spent six hours and twenty-seven minutes outside with Anil Menon, installing mounting hardware on the station's 3B power channel and routing cable for a seventh roll-out solar array — added power NASA describes as supporting the station's critical systems through to its safe, controlled deorbit. On September 1 she was out again, riding Canadarm2 alongside ESA astronaut Sophie Adenot during a navigation and science maintenance spacewalk. That was the fourth station spacewalk in a single month.
Forty years after that one photograph, the job doesn't seem to be about how far a person can drift. It's about how reliably they can come back out and do it again a few weeks later.
Detailed view of an astronaut's EVA spacesuit and Portable Life Support System backpack in space.
What This Adds Up To
Right now, somewhere overhead, the station keeps circling, and astronauts keep going outside to check equipment, swap failed parts, and bolt on new hardware. None of them fly free the way McCandless did. They stay connected to something the whole time — a hand on a rail, boots in a restraint, a tether on the harness. But turning a wrench between that much black and that much blue must still be its own kind of astonishing, and its own kind of frightening.
I imagine both feelings sit in one body at once: the tightness of a place that forgives nothing, and the quiet pride of being the one pair of hands doing the touching for the rest of us. Maybe that's the closest thing to happiness a person can find that far from home.
Female astronaut modifying the International Space Station power system near a rollout solar array.
Frequently Asked Questions
What else does the space station's robotic arm do, besides help with spacewalks?
Besides helping position spacewalkers, Canadarm2 moves visiting cargo spacecraft, station modules, and external hardware. It carries a latching end effector at each end, which lets the arm release one grapple fixture and take hold of another, effectively walking itself from point to point around the station's exterior.
Are astronauts also training for spacewalks on the Moon?
Yes, with one important limit. NASA uses the Neutral Buoyancy Laboratory to rehearse tools, procedures, and team coordination, while virtual reality, spacesuit simulators, a lighting lab that mimics the lunar south pole's extreme angles, and geology field exercises cover the conditions a pool cannot. Water does not reproduce the Moon's one-sixth gravity. What it offers is a controlled place to practice complex work.
When did NASA start training astronauts underwater for spacewalks?
NASA's Neutral Buoyancy Laboratory was formally dedicated in 1997, after the first suited astronaut training dives there in 1996. It has been NASA's principal spacewalk training facility since it became operational.
Sources & References
NASA, "40 Years Ago: STS-41B, the First Flight of the Manned Maneuvering Unit" — nasa.gov
NASA, "Astronauts Begin Spacewalk to Repair Canadarm2 Robotic Arm," 2026 — nasa.gov
NASA, "Astronauts Repair Canadarm2 Robotic Arm and Complete Spacewalk," 2026 — nasa.gov
NASA, "Astronauts Complete Spacewalk for Solar Array Modifications," 2026 — nasa.gov
NASA, "Station Crew Cleans Up, Relaxes After Busy Month of Spacewalks," 2026 — nasa.gov
NASA, "International Space Station Facts and Figures," 2023 — nasa.gov
NASA, "11.0 Spacesuits," 2025 — nasa.gov
NASA, "EVA Systems," 2024 — nasa.gov
NASA, "Crew & Operations Training," 2024 — nasa.gov
NASA, "NASA Sharing Underwater Training Facility With Petroleum Industry," 2023 — nasa.gov
NASA, "A SAFER Way," image article on the emergency propulsion backpack — nasa.gov
NASA, "International Space Station Spacewalks," 2023 — nasa.gov
NASA, "Spacewalking With Scott Wray," 2026 — nasa.gov
NASA, "Mobile Servicing System," International Space Station reference — nasa.gov
NASA, "Building on a Mission: Neutral Buoyancy Facilities for Spacewalk Training" — nasa.gov
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