Artemis II Is About to Make History
When we last checked in back in February, NASA had just encountered a hydrogen leak during Artemis II’s first wet dress rehearsal and pushed the launch window to March. A lot has happened since then (including another delay), but the good news is that as of today, the countdown clock is ticking and we are less than 24 hours from the first crewed lunar mission in over 50 years.
Let’s catch up on everything that's happened and look ahead at what to expect when this rocket finally lights up the Florida sky.
Our last update covered the first wet dress rehearsal on February 2, which uncovered a hydrogen leak at the tail service mast umbilical and pushed the launch from February into March. NASA’s team got to work, replaced two seals at the flight-ground interface, and by February 19, they were ready for round two.
The second wet dress rehearsal went about as well as anyone could have hoped. Launch controllers successfully loaded hundreds of thousands of gallons of cryogenic propellant into the SLS, ran through simulated countdown procedures, and demonstrated the kind of clock recycles and scrub procedures they’d need on launch day. The hydrogen leak issue? Resolved. NASA officials were so pleased with the results that they announced a tentative March 6 launch date the very next day.
And then, just when it seemed like things were on track, the universe reminded everyone that rocket science is, well, rocket science.
Late on the evening of February 20, barely a day after the successful second wet dress rehearsal, engineers discovered an interruption in the flow of helium to the SLS rocket’s Interim Cryogenic Propulsion Stage, or ICPS. That’s the upper stage of the rocket, and helium plays a critical role there: it maintains proper environmental conditions for the engine and pressurizes the liquid hydrogen and liquid oxygen propellant tanks. Without reliable helium flow, the upper stage simply cannot do its job.
Frustratingly, the helium system had worked fine during both wet dress rehearsals. This was a new problem that surfaced during routine operations afterward.
NASA Administrator Jared Isaacman identified several possible culprits: a blocked filter between the ground equipment and the rocket, a malfunctioning valve in the upper stage, or an issue with the quick-disconnect umbilical that detaches from the rocket during liftoff. A similar valve-related helium issue had cropped up before the Artemis I launch in 2022, so this wasn’t entirely uncharted territory, but it still required hands-on access to components that can only be reached inside the Vehicle Assembly Building.
That meant rollback.
On February 25, the 322-foot SLS rocket and its mobile launch platform began the slow, four-mile journey from Launch Pad 39B back to the VAB aboard Crawler Transporter-2. The trip took roughly 12 hours. Once inside, technicians lowered access platforms in High Bay 3 to reach the upper stage and begin diagnosing the problem. While they were at it, they also replaced batteries in the flight termination system and the upper stage, taking advantage of the downtime to knock out maintenance that would have been needed eventually anyway.
The March launch window was officially off the table. The next available opportunity was April 1.
For those of us who had been watching NASA gear up for a March launch, it was a disappointing setback. But if there’s one thing the Artemis program has taught us, it’s that patience and thoroughness are non-negotiable when you’re putting people on top of a rocket. Just like with the Artemis I campaign (which saw the SLS rolled off the pad three times before finally launching in November 2022) the team was determined to get it right.
After weeks of repairs and testing inside the VAB, NASA rolled the Artemis II stack back to Launch Complex 39B on March 20. The overnight journey began at 12:20 a.m. EDT and took about 10 hours, with the crawler transporter making the four-mile trek at its signature pace of roughly one mile per hour.
With the rocket once again standing at the pad, the ground team got to work securing the stack to the pad infrastructure, reconnecting power and communications, and preparing the cryogenic systems for what everyone hopes will be the final fueling before launch.
Meanwhile, the four-member Artemis II crew had already entered their pre-launch quarantine on March 18. Commander Reid Wiseman, Pilot Victor Glover, Mission Specialist Christina Koch, and Canadian Space Agency astronaut Jeremy Hansen flew to Kennedy Space Center on March 27 aboard T-38 jets, arriving at the Launch and Landing Facility for the final stretch of preparations.
On Sunday, March 30, the countdown clock officially started ticking at 4:44 p.m. EDT, counting down toward a targeted launch time of 6:24 p.m. on Wednesday, April 1. Members of the launch team took their positions at consoles inside the Rocco Petrone Launch Control Center.
Engineers are now powering up the flight hardware, checking communication links, and preparing for the precise fueling sequence that will load the SLS with super-cooled liquid hydrogen and liquid oxygen. At the pad, teams are filling the sound suppression system’s massive water tank. That system will unleash a protective deluge at liftoff to shield the vehicle from the intense acoustic energy of its own engines.
The weather forecast is looking favorable, with an 80% chance of acceptable conditions, with the primary concerns being cloud coverage and potential ground-level winds. If weather or technical issues force a scrub on April 1, backup launch opportunities exist on April 2 through April 6 and again on April 30.
The crew has been following a controlled sleep schedule and nutrition plan in quarantine, staying healthy and mission-ready while receiving regular updates on the rocket’s status.
For those who want to know what the 10-day mission will actually look like once the SLS clears the tower, here’s a look at the plan.
About eight minutes after launch, the SLS core stage will separate, and the ICPS upper stage will perform a series of burns to place Orion into a high elliptical orbit around Earth. The crew will spend their first day in orbit checking out Orion’s life support systems (the potable water dispenser, the carbon dioxide scrubbing system, the toilet), which all need to work perfectly to keep four people alive in deep space.
During this phase, Pilot Victor Glover will take manual control of Orion for one of the mission’s most anticipated demonstrations, proximity operations with the spent ICPS. Once the upper stage separates from Orion, Glover will fly the capsule around and near the discarded stage, practicing the close-formation maneuvers and rendezvous techniques that future Artemis missions will need when docking with the Gateway lunar station or the SpaceX Starship landing system.
On flight day two, Mission Specialist Christina Koch will prepare the spacecraft for the main event: the translunar injection burn. Orion’s main engine on the European Service Module will fire, accelerating the spacecraft out of Earth orbit and onto a free-return trajectory to the Moon. Once committed to this path, the crew is coming back whether they want to or not. The trajectory is designed to swing them around the far side of the Moon and bring them home without requiring any additional engine burns, a safety measure borrowed from the same principles that saved the Apollo 13 crew in 1970.
Over the following days, the crew will perform trajectory correction burns, demonstrate CPR procedures in microgravity, test medical equipment, exercise to stress-test the life support systems, and make geological observations as they pass within roughly 5,000 miles of the lunar surface. The crew will also participate in the AVATAR experiment, which uses organ-on-a-chip devices to study the effects of radiation and microgravity on human tissue.
After swinging around the Moon, Orion will head back toward Earth and re-enter the atmosphere for splashdown in the Pacific Ocean, completing an approximately 10-day journey that will have covered more than 600,000 miles.
Artemis II is a test flight, and everything about it is designed to prove that NASA’s hardware and its crew are ready for what comes next. If the mission succeeds, NASA will turn its attention to an additional test flight, which will be a lander checkout mission planned for next year. All of that has to occur before attempting an actual crewed lunar landing on Artemis III, potentially in 2028.
The road ahead is long and expensive. The Artemis program has already cost an estimated $93 billion, and getting boots on the lunar surface will require continued Congressional funding and successful development of the Starship Human Landing System. Tomorrow’s launch is the moment where the Artemis program proves it can safely carry humans into deep space.
Gear Up for Launch Day
Want to commemorate this exciting mission? The Space Store has you covered with official NASA Artemis II merchandise, including apparel, accessories, and drinkware.
Includes crew member names: Reid Wiseman; Victor Glover; Christina Koch; Jeremy Hansen
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Pre-shrunk cotton, available in 3 colors.
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This white glossy mug is perfect for whatever you’re drinking. Lead and BPA-free ceramic, and made-to-order.Â
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Check out our whole collection of Artemis II merchandise at The Space Store and stay tuned for more updates as NASA works toward that March launch window. History is just around the corner.