NASA fully loads Artemis 1 rocket with fuel in successful 'wet' rehearsal

June 20 (UPI) -- NASA's fourth attempt Monday to complete a practice launch day exercise for its huge uncrewed moon rocket Artemis 1 was deemed a success at the Kennedy Space Center in Florida.

Crews were able to fully load the rocket with super-cold liquid hydrogen propellent and successfully reach the "terminal count" phase for the first time before the countdown was automatically paused at T-minus 29 seconds.

"It's a great day for our team," said launch director Charlie Blackwell-Thompson. "Definitely a good day for us and a very exciting day as well."

The successful wet dress rehearsal came after three failed attempts in April, forcing contractors to fix hardware and update software on the spacecraft. Monday's trial was another attempt to prove the rocket could be safely loaded with propellant and to make sure launch day procedures, without actually launching, go smoothly.

The overriding goal for in the latest attempt was to reach terminal count," Blackwell-Thompson said. "We have done this many times in a 'sim,' but we haven't done it with the cryogenic mix on the vehicle. So today we got all stages to replenish -- that was a big milestone for us."

Both the team and the hardware "performed very well," she added.

NASA needed a successful test to complete the data needed to set an official launch date, which could come later this summer.

Before Monday's rehearsal, NASA said there are three new issues under evaluation, including a "small grass fire" near the hydrogen flare stack at launch pad 39B, as well as a possible hydrogen leak in a quick disconnect on the SLS core stage.

"We're feeling really good," Wes Mosedale, technical assistant to NASA's Artemis 1 launch director, said earlier in the day. "The liquid hydrogen tank is now 100% full on the SLS core stage. Liquid oxygen is 80% loaded onto the core stage."

A previous wet dress in April was cut short after NASA had to scrub the test due to valve, fueling and leaking issues. The rocket was rolled back to the Vehicle Assembly Building for troubleshooting and repairs.

"Rolling back was absolutely the right thing to do to be able to work through the issues we found at the pad," Jim Free, NASA's associate administrator for the Exploration Systems Development Mission Directorate, said during a news briefing last month.

NASA made a total of three attempts to complete the wet dress rehearsal, but each attempt was plagued by some sort of glitch with the rocket, the mobile launch platform or the ground system equipment that supplies the rocket with fuel.

SLS is designed to launch NASA's return to the moon. The mission is to provide data on how the Artemis rocket performs in deep space, and ultimately will pave the way for future crewed flights around the moon and to the lunar surface, NASA officials have said.