TENERIFE, CANARY ISLANDS — NASA's Artemis II astronauts were just minutes away from a critical engine burn that would send them toward the moon when an unexpected cabin leak warning threatened to change the course of their historic mission.
"If it had happened five minutes later, we may not have been able to have that burn," Artemis II pilot Victor Glover revealed during an Oct. 18 discussion with Canadian former astronaut Chris Hadfield at the Starmus VIII festival here in Tenerife.
The incident unfolded on April 2, the second day of the Artemis II mission, as the astronauts' Orion spacecraft swooped back toward Earth after traveling some 38,000 miles (61,000 kilometers) away. Orion had been completing a highly elliptical orbit around Earth, giving the crew and mission control an opportunity to test the capsule's systems before committing to the journey to the moon. Orion was now approaching its closest point to our planet, roughly 100 miles (160 km) above the surface, ahead of the crucial translunar injection (TLI) burn that would send the astronauts moonward.
"Jeremy looks out the window and says, 'I think we're going to run smack dab into the middle of Earth,'" Glover recalled, referring to Artemis II mission specialist Jeremy Hansen of the Canadian Space Agency. "Because we were getting so low."
The close approach brought additional challenges, as Orion passed through a region populated by orbital debris and satellites.
"The density of things is going up from where we are, and also an increase in radiation," Glover explained.
It was at this particularly demanding point in the mission that Orion issued a warning that indicated a possible cabin leak, around 15 minutes before the critical TLI burn.
"So, determining whether it was real or not was a big deal," Glover said.
The crew and mission control faced a crucial question: Was it safe to continue heading to the moon, or would they have to abandon the planned maneuver and cut the mission very short? "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?" Glover recalled.
The timing was particularly critical. The TLI burn was designed to propel Orion out of Earth orbit and onto its trajectory around the moon, marking the first time astronauts had headed toward Earth's nearest neighbor since the Apollo era.
Luckily, as NASA flight director Judd Frieling told us during an April 2 media briefing, the warning turned out to be a false alarm.
So Artemis II received the go-ahead. Orion fired its main engine for approximately five minutes and 50 seconds, successfully setting the four astronauts on their journey around the moon.
"We're watching the timer count down, velocities go up, and the magenta and green numbers coming together," Glover recalled.
"Everything is tracking. It's looking good."
Before long, the crew had broken free of Earth's gravitational hold and were hurtling toward the moon at around 24,500 mph (39,430 kph).
Despite the tense moments before the burn, Artemis II went on to make history. NASA astronauts Reid Wiseman (the mission's commander), Glover (pilot) and Christina Koch (mission specialist), along with Hansen, traveled farther from Earth than any humans before them, reaching a maximum distance of 252,756 miles (406,771 km) during their journey around the moon.
The four astronauts returned safely to Earth on April 10, splashing down in the Pacific Ocean off the coast of San Diego after nearly 10 days in space.
