NASA has delayed a critical fueling rehearsal and shifted the earliest possible launch date for the Artemis II mission because of forecast near-freezing temperatures at the Florida launch site.
The wet dress rehearsal, a full countdown and tanking test for the Space Launch System Moon rocket, will now occur Monday. With the change, the first opportunity to launch moves to 11:20 p.m. EST on Feb. 8, and NASA has given up chances on Feb. 6 and Feb. 7. If liftoff does not occur by Feb. 11, the flight will slip to early March.
The schedule shuffle follows guidance that very cold ambient conditions can complicate cryogenic operations and systems on the pad. The adjustment preserves time for analysis of Monday’s tanking data before attempting to send four astronauts on the first crewed voyage to the lunar vicinity in more than five decades.
What is changing this weekend
The rehearsal timeline now begins with a quiet countdown start at 8 p.m. EST Saturday. Controllers will hold the rocket at the pad through the weekend, then begin loading propellants around 11 a.m. Monday, with a simulated launch window opening at 9 p.m. Monday.
The exercise gives engineers a chance to verify tanking procedures, run through terminal countdown steps, and practice recycle options that would be used to troubleshoot unexpected issues on launch day.
NASA’s temperature rules for both rehearsal and launch are strict in cold snaps. Tanking requires the outside temperature to stay above a specified threshold for a sustained period, and average conditions must remain above a set point to protect systems and ground crews. Those constraints, combined with a forecast dip into the 30s, prompted planners to move the fueling test off the weekend.
What the test will prove
The Space Launch System uses supercold liquid hydrogen and liquid oxygen, not methane, and takes on more than 730,000 gallons of these propellants across the core stage tanks. Monday’s rehearsal is meant to confirm that valves, vents, lines, and umbilicals remain leak-tight and responsive throughout loading, replenish, and prelaunch conditioning.
The team will also practice countdown holds and quick turnarounds to ensure procedures are in place if they need to recycle on launch day.
Artemis II is the second flight of the SLS and the first with a crew aboard Orion. Before the uncrewed maiden launch in 2022, NASA conducted multiple fueling tests to chase down hydrogen leaks and ground-system issues, then incorporated fixes for this flight. Monday’s rehearsal is designed to validate those upgrades with a full-up tanking that mimics launch day conditions as closely as possible without lighting the engines.
The crew and the mission
Four astronauts are assigned to the nine- to ten-day lunar flyby: Reid Wiseman, Victor Glover, Christina Koch, and Jeremy Hansen of the Canadian Space Agency.
The mission will take Orion around the Moon and back, exercising life support, communications, navigation, and deep-space operations that will be needed for a later landing attempt near the south pole.
The crew remains in quarantine and continues final simulations while the launch team works the weather and rehearsal plan. A clean wet dress on Monday, followed by satisfactory data reviews, would keep the door open for the first attempt on the night of Feb. 8, with additional opportunities currently identified on Feb. 10 and Feb. 11.
