Spacewalks on the ISS

In March of 2019, social media lit up with the promise of the first all-female spacewalk. Unfortunately, the spacewalk fell through due to spacesuit issues, but it captivated the public.

In the months since, people have been wanting to know more about spacewalks on the International Space Station (ISS). There have been over 200 spacewalks on the ISS, with many more scheduled to come as NASA prepares for manned Moon missions by 2028.

What is a spacewalk?

A spacewalk happens any time a human being exits a vehicle in space. NASA officially calls this extravehicular activity, or EVA.

There are three main reasons we conduct spacewalks. First, to work on the exterior of a spacecraft, usually for maintenance or repairs. Second, to test new equipment. And third, to repair passing satellites, which is easier to repair in space than on Earth.

ISS has three types of spacewalks. Scheduled spacewalks are part of the mission. Unscheduled spacewalks come up as needed, not as part of the mission, but as a necessity for repairs. Contingency spacewalks are unscheduled, but they’re more urgent, usually as a dire need to protect the crew’s safety.

The first spacewalk occurred in 1965. Cosmonaut Alexei Leonov of Russia was in the vacuum of space for 10 minutes. The first American astronaut to do so was Ed White during the 1965 Gemini mission. Russian cosmonaut Anatoly Solovyev holds the record for the most spacewalks, with 16 total under his belt.

How does a spacewalk work?

Astronauts work in a very different environment during spacewalks. Because of this, they go through intense training on Earth to prepare for their mission. They must learn to account for the lack of gravity and how their body moves in space.

While they’re on Earth, astronauts train at NASA’s Houston headquarters in a large pool, where they spend up to 7 hours a day. They also train using virtual reality (VR) to practice the intricacies of the spacewalk and conducting repairs.

The spacewalk process takes almost an entire day. The spacewalk itself can last anywhere from 4 – 8 hours. Before the spacewalk, astronauts don their spacesuits to pressurize for several hours. This eliminates the nitrogen in their body so bubbles won’t form in their blood while working in the vacuum of space.

If they didn’t eliminate this nitrogen, they would experience the bends, an affliction common in scuba divers that resurface too quickly.

NASA treats the spacesuits not as suits, but as actual vehicles. They’re officially called extravehicular mobility units, or EMUs. Spacesuits weigh about 250 pounds empty and they’re made up of 14 layers of pressure, heating, cooling, and other important systems that protect astronauts.

Once the astronauts pressurize inside the suits, they go through an airlock to get outside the ISS. They remain tethered to the craft with 55-foot cables. Astronauts also tether tools to their suits and use footholds on the exterior of the ISS to get around.

In the event of an emergency, astronauts have a SAFER pack on their suit, which is a backpack with thrusters. If the astronaut becomes untethered, he or she can fly back to the ISS.

After completing several hours of work, the astronauts return to the ISS. During this time, they again have to depressurize for several hours to prevent decompression sickness.

The future of space travel

Spacewalks are critical to the future of human exploration. They’re used to repair and maintain critical spacecraft as well as further our knowledge of the human body in space. It may be no cakewalk, but spacewalks are the key to our future in space.