By BlueShift | 2026-03-25

As a team at the Johnson Space Center monitored them from Houston, Texas, NASA astronauts Jessica Meir and Chris Williams exited the International Space Station (ISS) airlock on March 18 for the first spacewalk of 2026.

The event, described as US spacewalk 94, was the first for ISS Expedition 74, and the first spacewalk for Williams. It was Meir's fourth spacewalk.

Spacewalks are officially known as Extravehicular Activities (EVAs).

Meir served as the lead spacewalker, identified as Extravehicular Crewmember 1 (EV1) and by the red stripes on her spacesuit, while Williams took the second spacewalker role, EV2.

From inside the ISS, Expedition 74 crew members Jack Hathaway (NASA) and Sophie Adenot (European Space Agency) played a supporting role.

After emerging from the ISS airlock carrying tools and equipment, including an eight-foot bag, the pair set out to install a solar array modification kit on the port side of the ISS.

They worked to prepare the 2A power channel for a future ISS Roll-Out Solar Arrays (IROSA) installation, completing their tasks in just over seven hours.

A subsequent EVA, US spacewalk 95, will prepare the 3B power channel.

The two additional Roll-Out Solar Arrays, which will be arriving at the ISS at a later date, will provide additional power for the orbital laboratory once they are installed, helping to extend the life of the station.

Meticulous planning and coordination

Spacewalks are lengthy and high-risk events conducted every few months to carry out necessary tasks related to station maintenance, upgrades or repairs.

They take place up to 12 times per year, with more than 275 spacewalks at the ISS since 1998, with a large number at the outset and annual numbers again trending upwards as the ISS ages and more maintenance is required.

Each spacewalk is meticulously planned and coordinated between the ISS crew and Mission Control in Houston, which monitors every step of the process.

For the astronauts, spacewalks take two weeks of onboard preparation, with planning on the ground beginning much earlier, Flight Operations Directorate spacewalk flight director Diana Trujillo said during a pre-EVA briefing.

This includes doing a dry run of the spacewalk to ensure all steps can be done "efficiently and effectively," preparing a plan A and plan B, preparing the space suits, and conferences with the crew to answer all questions, she said.

"Every EVA is different," said Flight Operations Directorate spacewalk flight director Ronak Dave. Timelines are flexible and driven by objectives, he added, noting that "every single time is a fun and unique challenge."

"Not all EVAs are equal in terms of what it takes to plan one and execute one," ISS Program operations integration manager Bill Spetch said during the briefing.

One of main things to mitigate is decompression sickness, with changes to the process driven by innovation and need, learning and improvement over time.

"Things can change any moment in a way we didn't expect," Trujillo noted.

Risk management and mitigation

Spacewalks are among the most dangerous tasks in orbit, according to NASA.

Because of the inherent risk, the ISS crew uses instruments such as the Canadian robotic arm (Canadarm2) for external work, where possible, limiting the need for astronauts to exit the station.

Spacesuits operate at a much lower pressure than the ISS cabin, so if an astronaut transitions too quickly, nitrogen dissolved in their blood and tissues can form bubbles, leading to joint pain, neurological issues or even death.

To accelerate the metabolic process of flushing nitrogen from their blood and prevent decompression sickness, astronauts must engage in an hours-long process of exercises, while breathing 100% oxygen, before a spacewalk.

Once outside the station, astronauts face threats from micrometeoroids -- tiny particles of space debris that can puncture spacesuits and cause oxygen leaks and depressurization.

They also face temperature fluctuations of up to 500 degrees Fahrenheit, in addition to the heavy physical toll that wearing a pressurized suit for hours can take on their bodies.

New technologies are being developed to improve safety on future missions and further mitigate these risks.