Four astronauts blasted off from Kennedy Space Center on Wednesday evening, beginning a 10-day journey around the Moon that will carry them farther from Earth than any human has ever travelled. But the true gamble of NASA's Artemis II mission won't play out in deep space. It comes down to the last minutes before splashdown, when the Orion capsule punches into Earth's atmosphere at roughly 25,000 mph.
That will mark the fastest crewed re-entry ever attempted. And the one barrier standing between the crew and temperatures of 2,760°C has already shown signs of failure.
A Heat Shield That Cracked Under Pressure
Orion's heat shield is built from AVCOAT, an ablative material descended from the coating used on Apollo capsules in the 1960s and 1970s. It is designed to char and flake away in a controlled fashion during re-entry, absorbing extreme heat so the spacecraft's internal structure stays intact.
That is how it was supposed to work. During the uncrewed Artemis I mission in 2022, engineers discovered that large sections of AVCOAT had broken off in jagged, uneven chunks instead of eroding smoothly.
NASA traced the cause to trapped gases inside the material. The 'skip re-entry' profile used on that flight, in which Orion dipped into the upper atmosphere before bouncing back out and re-entering a second time, gave thermal energy enough time to build up between passes and crack the shield from within.
Post-flight inspections revealed more than 100 locations where ablative material had broken free.
A Changed Flight Path, Not a Changed Shield
NASA did not replace the heat shield for Artemis II. Instead, the agency altered the re-entry trajectory, eliminating the skip profile in favour of a steeper, more direct descent. This cuts the time Orion spends exposed to peak temperatures but increases the deceleration forces the crew will endure on the way down.
The agency ran more than 1,000 simulations and said its modelling confirmed the capsule would hold safe thermal margins even in worst-case scenarios. Since the Artemis II shield was already installed, NASA opted against a hardware redesign, relying instead on the modified flight path to ensure trapped gases vent naturally through the char layer.
A fully redesigned heat shield with improved material permeability won't fly until Artemis III, currently targeted for 2028.
Records and Firsts, All on One Flight
The crew launched aboard NASA's Space Launch System (SLS) rocket at 6:35 p.m. EDT on 1 April from Launch Complex 39B.
Commander Reid Wiseman, Pilot Victor Glover, and Mission Specialists Christina Koch and Jeremy Hansen of the Canadian Space Agency (CSA) are expected to travel roughly 252,800 miles from Earth, breaking the distance record Apollo 13 set in 1970 at 248,655 miles.
Glover is now the first Black astronaut to fly beyond low-Earth orbit. Koch is the first woman to travel to the Moon's vicinity, and Hansen is the first non-American to make the journey.
A Toilet Warning and the Road Home
Hours after launch, as the crew began setting up Orion for life in space, they tested the spacecraft's Universal Waste Management System. The 3D-printed titanium toilet is the first waste system on a lunar mission to allow astronauts to process liquid and solid waste at the same time.
During checkout, the crew reported a blinking fault light. NASA Associate Administrator Amit Kshatriya later described it as a 'controller issue' and said teams on the ground were working to resolve it.
'That one 24-hour orbit gives us time to check out all of Orion's environmental control, life support systems,' Commander Wiseman said before launch. 'Can it keep us alive? Can we drink water? Can we go to the bathroom?'
The crew will spend a full day orbiting Earth before a trans-lunar injection burn sends them toward the Moon.
If every system holds, they will swing behind the lunar far side and return for a splashdown in the Pacific Ocean off San Diego around flight day 10.
The heat shield gets its verdict then.
