After three years of delays, heat shield investigations, and engine swaps, four astronauts are sitting on top of a Space Launch System rocket at Kennedy Space Center waiting to go to the Moon. Artemis II launches today, and for the first time since Apollo 17 in December 1972, humans will leave low Earth orbit.
The crew: Reid Wiseman, 50, commander. Victor Glover, pilot, and the first person of color to leave low Earth orbit. Christina Koch, mission specialist, the first woman to do the same. Jeremy Hansen, Canadian Space Agency, the first non-US citizen to travel beyond low Earth orbit and into the Moon's vicinity. Their trajectory is a free-return loop around the Moon, coming within 4,700 miles of the lunar surface before swinging back for a Pacific splashdown approximately ten days after launch. The heat shield that protects them will have to handle reentry at about 25,000 miles per hour.
Artemis II has been pushed back repeatedly. The initial target was September 2025. NASA delayed it to April 2026 citing the heat shield investigation from Artemis I, when more than 100 areas on Orion's heat shield ablated differently than models predicted. The agency diagnosed the root cause in October 2024 and cleared Artemis II to fly without a heat shield fix already in place. An RS-25 engine swap added more schedule pressure: engine E2063 was replaced with E2061 in April 2025 after a leak was discovered in its oxygen valve hydraulics. The rocket's core stage stacking was delayed more than two months beyond its original September 2024 target and was not complete until October 2025.
The weather forecast is holding. Eighty percent probability of favorable conditions for launch at 22:24 UTC, with cumulus clouds, ground winds, and solar weather as the primary concerns. Rollout from the Vehicle Assembly Building happened March 20, a one-day slip from the original March 19 target due to an electrical harness issue on the flight termination system of the SLS core stage.
What the crew is flying in is Orion CM-003 Integrity, with European Service Module ESM-2 built by Airbus. Recovery will be by U.S. Navy from a San Antonio-class amphibious transport dock ship in the Pacific Ocean. The mission that follows, Artemis III, has been pushed to mid-2027 and the human landing system is still not qualified. Artemis II is flying without that problem to solve, and without a lander to get anyone to the surface.
The heat shield ablation findings from Artemis I were specific and unresolved. Orion flew the mission without a design fix. The 100-plus areas that performed differently than expected remain an open question on a vehicle carrying four humans at 25,000 miles per hour toward a planet with no atmosphere to slow them down. That is the engineering context the launch announcement does not contain.
The 54-year gap between Apollo 17 and Artemis II is real, and the milestone record the crew will set is real. So is the open heat shield question. Those two facts are not in tension. The mission can be historic and the engineering still have loose ends.