But excessive hydrogen quickly built up near the bottom of the rocket. Hydrogen loading was halted at least twice as the launch team scrambled to work around the problem using techniques developed during the previous Space Launch System countdown in 2022. That first test flight was plagued by hydrogen leaks before finally soaring without a crew.

The four astronauts assigned to the mission — three Americans and one Canadian — monitored the critical dress rehearsal from nearly 1,000 miles (1,600 kilometers) away in Houston, home to Johnson Space Center. They have been in quarantine for the past 1½ weeks, awaiting the practice countdown’s outcome.

Monday’s fueling demo will determine when they can blast off on the first lunar voyage by a crew in more than half a century.

At best, NASA could launch commander Reid Wiseman and his crew to the moon no sooner than Sunday. The rocket must be flying by Feb. 11 or the mission will be called off until March. The space agency only has a few days in any given month to launch the rocket, and the extreme cold already has shortened February’s launch window by two days.

Advertisement

Advertisement

Running behind because of the bitter cold snap, the countdown clocks began ticking Saturday night, giving launch controllers the chance to go through all the motions and deal with any lingering rocket problems. The clocks were set to stop a half-minute before reaching zero, just before engine ignition.

The nearly 10-day mission will send the astronauts past the moon, around the mysterious far side and then straight back to Earth, with the goal of testing the capsule’s life support and other vital systems. The crew will not go into lunar orbit or attempt to land.

NASA last sent astronauts to the moon during the 1960s and 1970s Apollo program. The new Artemis program aims for a more sustained lunar presence, with Wiseman’s crew setting the stage for future moon landings by other astronauts.

More in Science

Weird bird mouths go all the way back to the first avian dinosaur

Popular Science

Something Strange Is Living—and Thriving—Below Fukushima’s Dead Reactors

Popular Mechanics

New Discovery In Laser Technology Could Change Everything For Quantum Computing

BGR

NASA is about to send people to the moon — in a spacecraft not everyone thinks is safe to fly

CNN

687

___

The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education and the Robert Wood Johnson Foundation. The AP is solely responsible for all content.