NASA Skips Final Rehearsal for Artemis II, Betting Everything on Launch Day

NASA's Artemis II SLS rocket arrived at Launch Pad 39B at Kennedy Space Center at 11:21 a.m. EDT on Friday, March 20, 2026, after an overnight crawl from the Vehicle Assembly Building. The journey — carried on crawler-transporter 2 at roughly 1 mile per hour over the four-mile crawlerway — took 11 hours. High winds delayed the start of rollout from the planned Thursday evening target, but the rocket made up time and reached the pad before noon.

This is the second time the Artemis II stack has rolled to the pad. The first attempt ended with a return to the VAB on February 26 after engineers found a seal obstructing helium flow from the ground support system to the rocket's upper stage. During the resulting weeks in the shop, NASA refreshed flight termination system batteries, replaced upper stage and core stage batteries, swapped a seal on the core stage liquid oxygen feed line, and retested the oxygen tail service mast umbilical plate. A wet dress rehearsal on February 21 had cleared the vehicle for propellant loading — the same test that uncovered the helium issue. No additional wet dress is planned; the next time SLS is fueled will be for launch.

Artemis II will carry four astronauts — NASA commander Reid Wiseman, pilot Victor Glover, mission specialists Christina Koch and Jeremy Hansen of the Canadian Space Agency — on an approximately 10-day lunar flyby. The crew entered quarantine in Houston at 5 p.m. CDT on Wednesday, March 18, according to NASA's update on crew quarantine. They will travel to Kennedy approximately five days before launch, continuing isolation from the astronaut quarters there.

The launch window opens April 1 at 6:24 p.m. EDT, with subsequent opportunities through April 6 and a final early-window date of April 30. NASA has described April 1 as the primary target. The constraints are not soft. Lunar-return trajectories are sensitive to departure energy, Earth-moon geometry, and recovery zone positioning — unlike low Earth orbit missions where a day or two of delay is often operationally manageable.

What makes this moment notable is what had to be solved to get here.

The uncrewed Artemis I flight in December 2022 returned with unexpected char loss on the Orion heat shield — chunks of ablative Avcoat material at the capsule base, where it is supposed to stay. NASA and an independent review team spent most of 2024 characterizing the problem, with NASA identifying the root cause as Avcoat generating gas pressure during reentry compression, and the original formulation did not allow enough of that gas to escape through the material's vent paths. The pressure buildup caused the char layer to flake off unevenly. NASA characterized the root cause in a December 2024 briefing and has since implemented a fix — modifying the material's internal gas pathways — which it says will prevent the same behavior on crewed return.

That is not a small engineering problem to have solved quietly. The seriousness of the char loss was not publicly disclosed for roughly eighteen months, until the NASA Inspector General published close-up imagery of the damage. The fix is in. The heat shield flew on Artemis I and the material behavior is now understood. But readers should know that this mission follows a non-trivial near-miss on the very system that keeps the crew alive on the way home.

Artemis II is not a landing mission — that is Artemis III's problem, currently slated for 2028. This one is the proving run: Orion life support at lunar distance, navigation and trajectory correction in translunar space, mission control tempo for a deep-space crew, and the integration of everything SLS and ground systems are supposed to do under crewed flight rules. It is also the first time humans will travel beyond low Earth orbit since Apollo 17 left lunar orbit in December 1972. Fifty-three years is a long time to go without going back.

The Artemis II rollout marks a critical milestone toward returning humans to lunar orbit. Whether Artemis II launches on April 1 or slips into late April, the next few weeks will tell whether the Artemis campaign has genuinely turned a corner — or whether SLS-era program discipline still has more schedule erosion to process before humans orbit the moon again.