Rocket failures, oxygen leaks, space debris and scorching heat: these are just a few of the risks that Nasa’s Artemis II astronauts face as the first humans
to return to the moon in more than half a century.

Since Nasa first attempted to send people beyond the safety of Earth, spaceflight has been a death-defying endeavour. The agency has always grappled with risky scenarios, from the flash fire of Apollo 1 in 1967 to the rocket thruster issues that recently extended the stay of the Boeing Starliner astronauts in orbit for extra months. Those dangers grow more intense the farther you get from home.

But the failures and close calls bring experience in predicting and preparing for the hazards of spaceflight.

“We will never get risk down to zero in this line of work,” Jared Isaacman, Nasa’s administrator, said in an interview.

Isaacman, who conducted a spacewalk on a private space mission he financed, said some risks are worth taking. “It’s the greatest adventure in human history,” he said. “I think it’s absolutely our destiny to go out and explore among the stars.”

For all the dangers faced by Nasa’s moon-bound crew, it is confident in the work that has been done to make the 10-day journey in the Orion spacecraft safe.

“I once joked that every lesson that has ever been learned in human spaceflight has been rolled into Orion,” Reid Wiseman, the commander of Artemis II, said in a Nasa podcast about the mission. “Every cable is a little bit thicker than it needs to be. Every computer has more redundancy than it needs to.”

Wiseman added, “You need those redundant and reliable systems” when flying into deep space.

Liftoff and early ascent

Orion is flying on Nasa’s giant Space Launch System rocket. After the uncrewed Artemis I mission in 2022, Artemis II will be the first time the rocket flies with astronauts on board.

“Crew safety is literally the prime directive,” said Carolyn Overmyer, an engineer at Lockheed Martin Space responsible for the technical integrity of Orion. “Whatever we do, crew safety is the thing that you have to think about first.”

The risks start before leaving the ground. Mission control pushed back the launch of Artemis I multiple times because of poor weather conditions and technical issues with the rocket, including a propellant leak.

With astronauts aboard for Artemis II, Nasa has an emergency escape system on the launchpad for pre-liftoff issues.

It resembles gondolas on a ski lift, designed for the crew to quickly get to the ground. Four baskets, each the size of a small SUV, can whisk the astronauts down a set of cables to the perimeter of the launchpad. They can then board emergency vehicles and drive away.

In January, the agency reported that the baskets stopped before reaching the pad perimeter during a test. Technicians adjusted the brakes.

But the most risk occurs as the rocket launches and begins its ascent.

“I will be holding my breath during that time,” Overmyer said.

In case of rocket failure in the first three minutes of flight, Orion is fitted with another escape system that will quickly eject the capsule from the rocket.

Orion will then reorient itself to land in the Atlantic Ocean.

Later in the flight but before the vehicle is in orbit, Orion can use its own engines for a similar purpose.

Space hazards

After nearly two hours, Orion will enter a high orbit above Earth, where the crew will test systems in flight for the first time. The crew will perform a piloting demonstration by flying Orion manually and simulating a docking manoeuvre.

Redundancies protect the crew during manual flight. If the hand controllers used to move the spacecraft malfunction on the pilot’s side, the commander can take over. Four solar panels power Orion’s electronics, though it can fully operate with just two. Three touch screens provide flight data to the crew, and a cursor control device allows the astronauts to interact with the software when their hands are unable to reach the screens.

It will also be the first in-flight test of Orion’s life support systems, which keep the capsule habitable for astronauts in space. This includes monitoring and maintaining temperature, humidity and pressure, as well as providing oxygen to the cabin, and removing carbon dioxide from it.

“We’ve tested it to death on the ground,” Overmyer said. “But it’s the first time we’re flying with it.” The systems are tested while in Earth orbit, which gives the astronauts an accessible off-ramp back home, should anything go wrong before they head to the moon.

Backup systems exist to control temperature, pressure and oxygen levels should any life support emergencies arise.

Impact with tiny meteoroids or fragments of debris from satellites pose another concern, though the chances are low. Even objects less than about 4 inches (10cm) in size can cause severe damage to a spacecraft. Last November, China delayed the return of three of its astronauts after discovering a window crack that experts suspect was caused by such a strike.

If all else fails, the astronauts can don their spacesuits, which are designed to keep them alive for up to six days by supplying air and maintaining pressure. The outer layer of the suits is also fire resistant.

On the second day of flight, Orion’s engine will send the capsule toward the moon. Eight auxiliary engines can perform all of Orion’s planned thrusts and manoeuvres as a backup to the main engine. But the trajectory is also what engineers call “free return”, another safety measure that ensures Orion will arrive back home by coasting on the gravity of the moon and Earth, without the need for fuel.

Orion is scheduled to lose contact with Earth for 30-50 minutes when it travels behind the moon, which will block signals to and from the spacecraft. Mission control on the ground will upload the latest navigation data to the crew just before this stage to aid the capsule’s return if the crew is unable to reestablish communications.

Surviving the heat

It will take about four days for the Artemis II astronauts to return home from their loop of the moon. Upon reentering Earth’s atmosphere, Orion will race toward the surface at more than 20,000mph (32,186kmh), withstanding temperatures close to 5000 degrees Fahrenheit (2760C) before landing off the coast of San Diego.

Orion’s heat shield is one of the most important safety measures of the mission. Made of material that transfers heat away from the spacecraft, the shield underwent more than 1000 tests on the ground before being used in space with Artemis I in 2022.

Damage to the heat shield during this mission prompted investigations by Nasa and independent experts, including 23 months of additional testing.

“We’re going to make sure that we’re staying within the bounds of the hardware,” Jeff Radigan, the lead flight director of Artemis II, said during a news conference for the mission in January. “That’s the right thing to do to keep our crew safe.”

Once through the heat of Earth’s atmosphere, parachutes will automatically deploy to slow the capsule before it splashes down. Landing in the ocean provides a softer cushion than the ground. Air bags around the top of Orion will inflate to keep the capsule upright after splashdown.

If the crew needs to suddenly leave Orion and drop into the ocean before a recovery team arrives, their suits are bright orange to be easily identifiable in the water. They are also equipped with survival kits.

At the news conference in January, mission directors stressed their commitment to getting the crew home safely.

“I got one job, and it’s the safe return of Reid and Victor and Christina and Jeremy,” John Honeycutt, who leads the Artemis II mission management team, said of the astronauts. “I consider that a duty and a trust. And it’s one I intend to see through.”

This article originally appeared in The New York Times.

Written by: Katrina Miller

©2026 THE NEW YORK TIMES