Describing it as a “very unusual day” aboard the orbiting outpost, Chris Williams said he and his colleagues immediately fell back on their training and “knew exactly what to do”.
Recounting the experience following his recent return from an eight-month mission in space, the flight engineer said the main concern had been the safety of the two Russian cosmonauts undertaking the repair.
Mr Williams was one of five members directed by Nasa’s mission control back in June to take refuge in their docked Dragon spacecraft in case they needed to escape quickly while the work was carried out.
They were also told to put on their spacesuits.
The rare safe haven procedure was in place for around two hours before the astronauts returned to the Nasa station, circling around 250 miles above the Earth.
Nasa said at the time it had given the instruction “out of an abundance of caution”, but also spoke of its ongoing concerns about cracks and leaks aboard the ageing facility, which is due to be retired in 2030.
The agency had worked with its Moscow-based counterpart Roscosmos to tackle the problem.
Mr Williams returned to Earth on July 26 after logging 241 days on his first space flight.
Recalling the incident during a news conference at the Johnson Space Centre in Houston, Texas, Mr Williams said: “That was certainly a very unusual day on station.
“It was not something that we were expecting to do.
LIVE: After 241 days in orbit, @astro_ChrisW returned home on July 26. Tune in as he recaps his eight months on the @Space_Station. https://t.co/9QTA6pAKrC
— NASA (@NASA) August 4, 2026
“We knew that there was some work going on… and that there were some cracks in the pressure vessel that they were investigating.
“But we sort of were going about our normal day until we were we were called up and told to go shelter in the Dragon.”
He added: “Now, thankfully, this is something that we talked about and planned for.
“You know, it’s certainly not a great feeling because you know my two crew mates are over on the Russian segment working in this compartment, and so you don’t you don’t feel great when your crew mates are over there on the other side.
“But we planned and prepared for a five-person shelter-in-place Dragon.
“When difficult situations like that come up, you fall back on your training, and we knew exactly what to do, and we also knew that the ground teams were working on how to make sure that we could get out of this situation as safely as possible.
“We were really thinking a lot about, like OK, what do we bring with us so that you know if we’re there for a couple hours, we have snacks and that sort of thing.”
However, at the same time the team were keeping their Russian colleagues – Sergei Kud-Sverchkov and Sergei Mikaev – “in our minds”.
Mr Williams went on: “It was definitely an unusual day. But you know, you kind of flip into that that mode where you fall back on your training.”
During his time in space, Mr Williams completed 3,856 orbits of the Earth and travelled a mammoth 102 million miles.
His work on the station included carrying out research for new cancer treatments.
He also completed two spacewalks to prepare for space station power system upgrades and to replace a faulty joint on a robotic arm.
Once bitter rivals in the space race during the Cold War, Russia and the US cooperate on the space station and other projects.
That relationship has been tested by tensions between the two countries, including over the Kremlin’s invasion of Ukraine in 2022.
Despite this, Washington and Moscow have continued to work together, with US and Russian crews flying to the station on each country’s spacecraft.
