No guarantees: Inside the biggest risks facing NASAs Artemis 2 crew

NASA's next trip around the moon will push four astronauts into the most demanding flight of their lives, a mission defined by enormous speeds, vast distances, and little margin for retreat.

Artemis II, the agency’s first crewed lunar flight in more than a half-century, will also be the first time humans test the Space Launch System rocket and Orion capsule together. The 10-day flight, which could launch as early as Feb. 6, is designed to send astronauts far beyond Earth's orbit before hurtling them home at blistering speed.

How well Artemis II manages its risks — untested hardware, deep-space distance, and limited escape options — will shape NASA's plans for future lunar landings and, potentially, human missions to Mars. A serious failure could revive long-standing questions about whether the dangers of deep space still justify sending people there.

"When we get off the planet, we might come right back home. We might spend three or four days around Earth. We might go to the moon," said Commander Reid Wiseman. "It is a test mission, and we are ready for every scenario."

Speed and distance

The numbers alone stretch human comprehension. The crew — Wiseman, Victor Glover, Christina Koch, and Jeremy Hansen — are expected to travel farther than any astronauts before them, reaching about 4,600 nautical miles beyond the moon.

At the end of the mission, Orion — which the astronauts have named Integrity — will slam into Earth’s upper atmosphere at roughly 25,000 mph, dozens of times the speed of sound. That would match the re-entry velocity of Apollo 10, whose crew returned at 24,791 mph in 1969.

The above video captures Orion during Artemis I, re-entering Earth's atmosphere and descending, from the perspective of a camera pointed out a spacecraft window.

"When you see numbers like Mach 39 at entry, when you see numbers like 38,000 miles, 250,000 miles," Wiseman said, "those are just insane. Numbers like those are just not numbers that humans generally think about."

Abort options and exit plans

NASA has built into the mission ways to bring the crew home if something goes wrong, from the first seconds of launch through the journey to the moon.

During ascent, flight controllers can change course based on how the mega moon rocket behaves. If an engine fails immediately after liftoff, NASA can still guide the capsule to a safe splashdown. A few minutes into the flight, they could skip the burn that sends Orion toward the moon and instead take another lap around Earth to troubleshoot.

If problems persist, the crew could opt out of the destination altogether and splash down off the coast of Baja California, Mexico.

"We would lose the lunar mission," said Judd Frieling, the Artemis II ascent flight director, "but we'd still make a mission and be able to check out all of the life-support systems."

Beyond Earth orbit, the mission’s main safety net lies in its trajectory. The burn that sends Orion toward the moon is designed to place the spacecraft on a free-return trajectory, allowing Earth’s and the moon’s gravity to swing it back home even if later engine burns fail. Smaller thrusters can correct a short burn or bend the spacecraft’s path back to Earth, without having to reach the moon at all.

Radiation and solar storms

Radiation poses one of the greatest dangers to the Artemis II crew as they travel beyond Earth's magnetic field.

Once Orion leaves low-Earth orbit, the astronauts will no longer benefit from the natural shielding that protects the International Space Station. Outside the Van Allen belts — two rings of intense radiation thousands of miles above Earth — space becomes far more hostile to both people and electronics, said Mark Clampin, NASA’s deputy associate administrator for science.

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"You’re also at the mercy of coronal mass ejections, which fire lots of high-energy particles into space from the sun," he said.

The risk is heightened because the sun is nearing the peak of its 11-year activity cycle. Engineers have outfitted Orion with radiation sensors, and the astronauts will wear measurement devices in their suits.

If the sun erupts, the crew can shelter in a compartment beneath the capsule's floor, surrounded by stowage bags that add shielding. NASA will rely on solar-monitoring satellites for early warnings. The astronauts will practice building the radiation shelter during the mission regardless of whether an emergency arises.

Communication blackouts

Distance introduces another challenge. During Orion’s closest pass around the moon, the spacecraft will slip behind the lunar far side, cutting off radio contact with Earth for about 45 minutes.

"I would love it if the entire world could come together and just be hoping and praying for us to get that acquisition of signal," said Glover, the mission’s pilot.

Planned blackouts are one thing; unexpected ones are another. During the uncrewed Artemis I mission, NASA lost contact with Orion for 4.5 hours because of failures at the Goldstone Complex in California, part of the agency’s Deep Space Network. The problems stemmed from aging hard drives, outdated software, and warning systems that failed.

NASA's largest antenna at Goldstone has been offline since an accident four months ago, but officials say the dish was never required for Artemis II and will not affect communications.

A heat shield under scrutiny

For many mission managers, the riskiest moment remains the return to Earth. During Artemis I, pieces of charred material flaked off Orion's heat shield as it endured the extreme temperatures of reentry.

An investigation found that while the shield performed its job — slowly burning away to carry off heat — gases in some areas built up faster than they could escape. Though alarming, NASA officials said in 2024 that the damage would not have harmed a crew.

"They would have not sensed any disturbance inside the vehicle, there would not have been any excessive heating on the structure, and the guidance would have put them exactly where the Navy needed to recover them," said Amit Kshatriya, a senior NASA official.

Still, NASA has modified Artemis II’s re-entry plan to reduce stress on the heat shield. By targeting a splashdown closer to San Diego, Calif., instead of Baja California, engineers can shorten the hottest portion of the descent.

Even with those changes, the final plunge carries risk — an unavoidable reality of human spaceflight, said John Honeycutt, who leads NASA’s mission management team.

"From an overall perspective," he said, "that’s just part of cheating gravity."