A False Alarm Almost Cut NASA's Artemis II Moon Mission Short

Fifteen minutes before Artemis II's astronauts would commit to the burn that sent them toward the moon, their spacecraft told them something might be wrong with the air they were breathing.

That's the moment pilot Victor Glover described during an Oct. 18 conversation with former astronaut Chris Hadfield at the Starmus VIII festival in Tenerife, Canary Islands. A warning flagged a suspected cabin leak aboard Orion, right as the crew approached the point of no return on a mission NASA had spent years building toward. "If it had happened five minutes later, we may not have been able to have that burn," Glover said.

The warning came on April 2, the second day of the mission, as Orion swung back toward Earth after venturing roughly 38,000 miles out. That loop was by design: before committing four astronauts to a trip around the moon, NASA wanted to put Orion through a highly elliptical practice orbit, giving the crew and mission control a chance to check the spacecraft's systems while still close to home. The maneuver brought Orion back down to about 100 miles above Earth's surface, close enough that mission specialist Jeremy Hansen, looking out the window, told the crew, in Glover's retelling, "I think we're going to run smack dab into the middle of Earth."

That altitude carries its own hazards. Glover said the crew was moving through a zone thick with orbital debris and satellites, with radiation levels climbing as they got closer to Earth. It was in the middle of that already demanding stretch that the cabin leak warning appeared, with the translunar injection burn, the engine firing that would send Orion out of Earth orbit and on toward the moon, just minutes away.

The stakes behind that warning were immediate and binary. Glover said the crew and mission control were weighing two very different outcomes: proceed with the burn and head to the moon, or treat the warning as real, suit up, and prepare to bring the mission home early. "Are we going to do a TLI and burn to go to the moon, or are we putting on our spacesuits to prepare to come back to Earth right now?" he recalled asking.

Flight director Judd Frieling told reporters at an April 2 media briefing that the warning turned out to be a false alarm. With that resolved, Orion got the green light. The spacecraft fired its main engine for about five minutes and 50 seconds, the burn that put the four astronauts on a trajectory toward the moon. Glover described watching the numbers converge on the display as the burn played out: "We're watching the timer count down, velocities go up, and the magenta and green numbers coming together. Everything is tracking. It's looking good."

From there, Orion broke free of Earth's gravity and accelerated to roughly 24,500 mph on its outbound path.

A close call on a historic flight

The near-miss sits inside what was otherwise a landmark mission. Artemis II carried NASA astronauts Reid Wiseman, Glover and Christina Koch, along with Hansen of the Canadian Space Agency, farther from Earth than any humans have traveled, reaching a peak distance of about 252,756 miles during their loop around the moon. It marked the first time astronauts had headed toward the moon since the Apollo program.

The crew spent nearly 10 days in space before splashing down in the Pacific Ocean off San Diego on April 10.

Glover's account, delivered months after the fact at a science festival rather than in a NASA press release, underscores how thin the margin was between a historic success and an aborted mission. A warning that arrived five minutes later, by his own estimate, could have forced the crew to scrub the burn and turn back before ever reaching the moon. Instead, it resolved as a false alarm with just enough time to spare, and Artemis II went on to become the farthest crewed journey from Earth in history.