‘Check his pulse one more time’: NASA accidentally airs ISS emergency test

It took nearly 90 minutes for NASA to confirm the false alarm.
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NASA astronaut and Expedition 68 Flight Engineer Woody Hoburg rides the Canadarm2 robotic arm while maneuvering a roll-out solar array toward the International Space Station's truss structure 257 miles above the Pacific Ocean. In the rear, is the SpaceX Dragon crew vehicle that docked to the Harmony module's forward port on March 3 carrying four SpaceX Crew-6 crew members.
NASA astronaut and Expedition 68 Flight Engineer Woody Hoburg rides the Canadarm2 robotic arm while maneuvering a roll-out solar array toward the International Space Station's truss structure 257 miles above the Pacific Ocean. NASA

NASA’s regularly scheduled International Space Station livestream gave viewers a brief, unintended scare last night. At 6:28PM EST on June 12, an unidentified speaker appeared to begin directing ISS crewmembers to treat a commander suffering from severe decompression sickness whose “prognosis… is relatively tenuous.” 

“Check his pulse one more time,” the person, likely a mission control flight surgeon, reportedly instructed over the broadcast according to NBC News.

The individual also advised astronauts to place their seriously ill colleague into a spacesuit supplied with pure oxygen in order to provide a “best effort treatment,” and even suggested the possibility of ordering an emergency evacuation in order to transport the commander to a hospital in Spain that included hyperbaric treatment facilities.

Decompression sickness, colloquially referred to as “the bends,” is most frequently experienced by divers transitioning too quickly between low- and high-pressure water depths, although extreme versions can occur in space when a spacecraft’s exterior pressure is nonexistent. In these situations, nitrogen bubbles form in a body’s arteries and blood vessels which block the flow of oxygen, nutrients, and blood. If treated in time, the worst symptoms a sufferer might experience are severe joint cramps. Depressurize too quickly, however, and the issue is almost instantaneously fatal due to brain hemorrhaging—as was sadly the case for three Russian cosmonauts aboard the Salyut-1 capsule in 1971.

[Related: NASA astronauts will scrape microorganisms off ISS during upcoming spacewalk.]

Knowing the severity of such situations, it took nearly an hour-and-a-half before concerned viewers could breathe a sigh of relief last night. At 8:05PM EST, NASA issued a statement on X confirming the 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… all remain healthy and safe.” According to NASA, there was a solid chance most ISS astronauts were actually asleep during the false alarm, since it occurred during the station’s “sleep period.”

It’s currently unclear how the audio was accidently piped through NASA’s ISS live stream. Popular Science has reached out for clarification and will update accordingly.

Last night’s false alarm unfortunately wasn’t the last headache for the agency. Earlier this morning, NASA announced its scheduled two crewmember ISS spacewalk needed to be postponed due to a (real) “spacesuit discomfort issue.”