Dress-rehearsal countdown underway for critical Artemis II moon mission rocket fueling test

Braving rare sub-freezing temperatures, Kennedy Space Center workers pressed ahead with a dress-rehearsal countdown Sunday, readying NASA's huge Space Launch System (SLS) rocket for a critical fueling test Monday to clear the way for launch on a flight to send four astronauts on a flight around the moon.

The countdown began Saturday evening and will continue through the start of a simulated launch window opening at 9 p.m. EST Monday. The test started two days late because of predicted arctic weather along Florida's Space Coast. The delay, in turn, pushed the launch of the Artemis II mission from Feb. 6 to no earlier than the night of Feb. 8 — which is Super Bowl Sunday.

Artemis II commander Reid Wiseman, Victor Glover, Christina Koch and Canadian astronaut Jeremy Hansen are in pre-flight medical quarantine at the Johnson Space Center in Houston. Assuming the fueling test goes well, they are expected to fly to the Florida spaceport later this week to prepare for takeoff.

In the meantime, the launch team planned to pump more than 750,000 gallons of supercold liquid oxygen and hydrogen fuel into the Space Launch System rocket's two stages on Monday to rehearse loading procedures while making sure the booster's tanks and propellant system plumbing are leak-free.

"This test will run the launch team ... through a full range of operations, including loading cryogenic liquid propellant into the SLS rocket's tanks, conducting a launch countdown, demonstrating the ability to recycle the countdown clock, and draining the tanks to practice scrub procedures," NASA said in a blog post. "These steps ensure the team is fully prepared for launch day."

During the ramp-up to the SLS rocket's maiden flight in 2022, multiple leaks and other issues forced repeated delays. But launch director Charlie Blackwell-Thompson said improvements and upgrades based on lessons learned gave the team a good shot at getting through the fueling operation Monday without any major problems.

The "wet dress" countdown called for propellants to begin flowing into the SLS rocket just after 11 a.m. Monday. If all goes well, the tanks in the 177-foot-tall core stage and the 45-foot-tall Interim Cryogenic Propulsion Stage, or ICPS, will be fully loaded and in "replenish" mode by around 4:30 p.m.

In a normal launch countdown, the crew would head for the pad shortly after fuel loading to strap in, check their pressure suits and verify good communications with the launch team. But no one will be on board for Monday's exercise. Instead, engineers plan to work through a variety of procedures that might be needed to cope with unexpected problems on launch day.

"This process simulates real-world conditions, including scenarios where a launch might be scrubbed due to technical or weather issues," NASA said in its blog post. "At the end of the test, the team will drain the propellant and review all data before setting an official target launch date."

Because of the constantly changing positions of the Earth and moon relative to each other, along with lighting conditions and other factors, NASA only has five launch opportunities in February. The first two, Feb. 6 and 7, are no longer available, in large part because of the fueling test delay.

The last three available launch days are Feb. 8, 10 and 11. If technical issues or the weather keep the SLS on the ground past Feb. 11, the Artemis II mission will slip to a fresh set of launch opportunities between March 3 and 11.