What's keeping the Artemis astronauts safe?

On April 1, four astronauts launched toward the Moon atop a controlled 8-minute explosion with the power of a small nuclear bomb. For the next nine days, the crew of Artemis II — Reid Wiseman, Victor Glover, Christina Koch, and Jeremy Hansen — will travel hundreds of thousands of miles through the vacuum of space. 

“Anybody that tells you that's a safe thing to do does not understand the risks,” said Paul Sean Hill, former NASA director of mission operations. 

NASA has not flown anything like Artemis II in over 50 years. Compared to a Shuttle flight or a visit to the International Space Station, the mission faces unique risks. But Hill, who also served as the lead Shuttle flight director for NASA’s return to flight after the Columbia tragedy, has confidence in Artemis II. He chaired an independent review team that looked into a potentially major issue with one of Artemis II’s spacecraft, and walked away reassured. 

“It will be done as safe now as it's ever been,” he said, “if not safer.”

Far from home

Though no spaceflight is without danger, Artemis II carries special risks. It is the first flight of the Artemis program to carry people on board. The mission’s crew capsule, Orion, and its launch vehicle have only flown together once before. At the time, Orion’s life support system was not fully installed. 

It has also been decades since NASA put astronauts beyond the low orbit of the International Space Station. The crew of Artemis II will travel roughly 1,000 times farther. While astronauts on the ISS can be back on the ground in a few hours if there is an emergency, the crew of Artemis II will not have that option for most of the flight — at certain points, they will be days, if not over a week, from home.

Yet NASA does not think about Artemis II as “safe” or “unsafe,” according to Hill. Instead, the agency considers missions in terms of risk. It weighs all the dangers of a flight and decides how much it needs to address each one. Instead of promising safety, NASA manages risk.

“When we're finished, it's still going to be scary. And half of our own community would probably scream,” Hill said, “if we put them on the rocket for the launch.”

A glaring flaw

On April 24, 2024, Hill walked into a room of NASA engineers with little doubt in his mind that Artemis II had a big problem.

Over a year before, NASA had launched its Artemis I mission to test the spacecraft that would carry future astronauts to the Moon. The flight was successful, overall: the launch vehicle performed almost exactly as expected, and Orion made it back in one piece. But when NASA looked at the crew capsule up close, they noticed a glaring flaw.

During Orion’s return through Earth’s atmosphere, material from the capsule’s heatshield had broken off in chunks. This shield is crucial for protecting crews from the blistering heat that comes with reentry at around 40,000 kilometers per hour (25,000 miles per hour). Though Orion had survived, there was a similarly problematic heatshield already installed on the crew capsule for Artemis II. 

NASA delayed Artemis to get to the bottom of the issue. It took over a year, but eventually, engineers arrived at an explanation they were confident in. That’s when the agency called in an independent review team, led by Hill, to check NASA’s solution. 

“I was expecting to wire-brush them and tell them never was it going to work,” said Hill. “I happily was surprised they had a better story.”

According to the NASA engineers, Orion’s heatshield was not porous enough. When it got hot, the shield released gas, and if those gases couldn’t filter to the surface, they built up pressure until the shield cracked. But Artemis II could avoid the kind of heating that led to this problem by flying a steeper path on reentry. With that change, the engineers said, Orion could fly as-is.

At first, some voices outside of NASA warned that this plan was not enough, including multiple former astronauts. Hill argues these critics were not working with all the information, however. The heatshield situation is so technically complex, he says, it took his team of experts weeks to understand it fully, even with NASA engineers helping them. This January, two concerned former astronauts met with Hill’s review team and agency engineers to discuss NASA’s solution together, and afterward appeared to accept the decision to fly the heatshield.

Francesco Panerai, an assistant professor of aerospace engineering at the University of Illinois Urbana-Champaign, came to the same conclusion. Panerai has worked on heat protection at NASA in the past, and he was initially surprised to see the heatshield had failed so visibly. But after NASA offered its explanation, his surprise was “smoothed out.”

“That’s what the data say,” he explained. “It can be flown safe, within acceptable risks.”

Future missions, including Artemis III, should not have this issue with their heatshields. In the meantime, NASA does not expect it to pose a problem for the Artemis II astronauts.

Designed for mishaps

This is just one example of the risks NASA has had to manage for Artemis II. 

Since every crewed spacecraft must eventually carry people for the first time, NASA tries to design for the unexpected. In an emergency, the spacesuits on Artemis II should be able to sustain astronauts for up to six days. Orion also carries more batteries, parachutes, and solar panels than it needs to function. Its software runs on four identical flight computers, in case there is a glitch in one of them.  

NASA has put humans on spacecraft that have been tested — but not proven — before. Astronauts rode on the very first Space Shuttle launch. During Apollo, astronauts flew on the third flight of the Saturn V rocket, even though it had multiple problems with its engines during the previous uncrewed mission. Artemis I similarly found issues with Orion’s heatshield, batteries, and life support, allowing NASA to catch them when the stakes were lower.

And once Artemis II is on its way to the Moon, the mission’s trajectory is designed to bring it back to Earth even if Orion hits a snag. During Apollo 13, that same flight plan saved the crew’s lives.

To fly or not to fly

According to Hill, at the end of the day, astronauts fly because they trust the people sending them. These experts have many opportunities to weigh in on Artemis II. Hill himself attended one of their checks on Orion, called a Flight Readiness Review. He was impressed by the attention to detail he witnessed. 

“This many years after the last Shuttle flight, the way they conducted business, it sounded like my memories of when we were at our best,” he said. With generations more experience, Hill added, “It's hard to imagine it's not safer than, say, Apollo was.”

As for Panerai, he will be watching Artemis II closely. “Even from a flight that does go smoothly and nothing happens, there are things to learn,” he said. “That's what drives exploration forward.”

But, if given the chance, would he fly on Artemis II?

“100%,” Panerai said.