By Joey Roulette

WASHINGTON (Reuters) – NASA said a “spacesuit discomfort issue” forced the cancellation of a planned spacewalk outside the International Space Station (ISS) by two U.S. astronauts on Thursday, roughly an hour before their repair mission was poised to begin.

NASA astronauts Tracy C. Dyson and Matt Dominick, two of the orbiting laboratory’s six U.S. astronauts, donned their spacesuits early on Thursday morning in preparation for a roughly six-hour trek outside the ISS for routine repairs and a science mission, as shown on a NASA live stream.

As other U.S. crewmembers prepped the two astronauts inside the station’s Quest airlock – the exit module separating the station’s interior from the vacuum of space – NASA astronaut Mike Barratt asked flight controllers in Houston for a private communications line to discuss a medical issue.

Minutes later a NASA spokeswoman speaking on the live stream said “today’s spacewalk will not be proceeding as planned.”

“The spacewalk today, June 13, at the International Space Station did not proceed as scheduled due to a spacesuit discomfort issue,” NASA later said on its website.

The spacewalk mission was poised to be NASA’s 90th in the space station’s 23-year history, and the second this year. It would have been the fourth spacewalk for Dixon, who first flew to space in 2007, and the first for Dominick.

It was not clear what caused the spacesuit discomfort or whether an independent astronaut medical issue was a factor.

Past spacewalks have been called off over issues with the station’s spacesuits, which were designed nearly half a century ago with only minor redesigns and refurbishments. NASA’s inspector general has said they are ripe for an upgrade, which NASA is paying Raytheon’s Collins Aerospace to do.

Before Thursday’s spacewalk cancellation, NASA on Wednesday night accidentally broadcast on its live YouTube feed a simulated emergency of astronauts being treated for decompression sickness on the ISS, raising public alarm about the health of U.S. crewmembers.

NASA said there was no real emergency and that “audio was inadvertently misrouted from an ongoing simulation where crew members and ground teams train for various scenarios in space and is not related to a real emergency.”