Spacewalks on the ISS

Published October 12, 2026 · Updated October 12, 2026

Stepping out into the vacuum to work

A spacewalk, or EVA (extravehicular activity), is any time an astronaut leaves the spacecraft with nothing but a suit for protection. Nobody on the ISS goes outside for fun: every spacewalk has a task list that has been months in the making. Since 1998, there have been more than 270 spacewalks to build, maintain and upgrade the station, more than for any other spacecraft in history.

Typical jobs include swapping out batteries and pumps, installing new solar arrays, mounting or removing experiments exposed to the vacuum, replacing cameras and antennas, and fixing leaks. The robotic arms could handle many of these tasks, but some jobs need human hands.

Two suits, two airlocks

The station has two ways to get outside, one for each segment:

Both are really one-person spacecraft: they carry their own oxygen, remove carbon dioxide, control temperature with water that flows through an undergarment lined with tubes, and come with radios, lights and cameras.

Getting ready: flushing nitrogen from the blood

Inside the station, the crew breathes ordinary air at the same pressure as at sea level. The suits, on the other hand, run at a much lower pressure so astronauts can bend their arms and hands; at full pressure, they'd be as stiff as an inflated balloon. Switching straight from one pressure to the other would do to an astronaut what happens to divers who surface too fast: nitrogen bubbles in the blood.

To prevent that, astronauts breathe pure oxygen for a good while before going out, which clears the nitrogen from their bodies. With the US suit, this is combined with exercise or with a night spent in the airlock at reduced pressure. Between suiting up, running checks and all the prep, the day starts many hours before the hatch opens.

How long a spacewalk lasts

A typical spacewalk lasts six to seven hours, with no food and just a water pouch inside the suit, with a straw near the mouth. The record belongs to Jim Voss and Susan Helms, who spent 8 hours and 56 minutes outside in March 2001 during a space shuttle mission to the ISS. It's the longest spacewalk in history.

Usually two astronauts go out together. One of them has red stripes on the suit so viewers can tell who's who in the video. Inside the station, one crewmate reads them the steps and another runs the robotic arm if needed. On the ground, flight controllers follow every move.

The dangers

• Extreme temperatures. In sunlight, surfaces get hotter than 100 °C (212 °F); in shadow, they drop below −100 °C (−148 °F). And the station switches from one to the other every 45 minutes.
• Micrometeoroids and space debris. The layers of the suit protect against tiny particles, but a larger fragment would be a serious problem. We cover this in space debris and the ISS.
• Sharp edges and tools. A cut glove is one of the most common worries, which is why gloves are inspected after every spacewalk.
• Suit failures. In July 2013, during a spacewalk, Italian astronaut Luca Parmitano's helmet started filling with water because of a fault in the cooling system. He had to make his way back to the airlock barely able to see or hear. The incident changed procedures: helmets now have an emergency breathing tube and an absorbent pad.

So they don't drift away, astronauts always stay tethered to the station, and their tools are tethered to the suit. Even so, losing things is common: over the years, several tools and bags have floated off and orbited for a while before reentering.

How they train

Every hour of a spacewalk is rehearsed many times on the ground. NASA uses a huge pool in Houston, the Neutral Buoyancy Laboratory, with full-size mockups of parts of the station underwater. Russia has a similar facility in Star City, near Moscow. Wearing suits weighted so they neither sink nor float, astronauts repeat the tasks until they've mastered them. More details in how astronauts train.

How to watch live

NASA streams spacewalks live, with views from the helmet cameras and the station's external cameras, plus commentary from mission control. It announces them a few days in advance. Whenever one is scheduled, we round up the streams in our live spacewalks section.

Frequently asked questions

How long does a spacewalk on the ISS last?

Usually six to seven hours. The record is 8 hours and 56 minutes, set by Jim Voss and Susan Helms in March 2001.

How many spacewalks have there been on the ISS?

More than 270 since 1998, to build, maintain and upgrade the station. No other spacecraft has needed so many.

Why do astronauts breathe pure oxygen before going out?

Because the suits run at a much lower pressure than the station. Breathing pure oxygen beforehand flushes nitrogen from the body and keeps it from forming bubbles in the blood, which is what happens to divers who surface too quickly.

What happens if an astronaut comes loose during a spacewalk?

They're always tethered. On top of that, the US suit has a small emergency jetpack to fly back to the station if the tether ever failed. It has never had to be used in a real emergency.

Can you watch spacewalks live?

Yes. NASA streams them using cameras on the helmets and on the station. When one is scheduled, we link to it in our live section.