Check out the final prelaunch test of the Artemis moon rocket

The fourth attempt at a final prelaunch test began on Saturday, with refueling of the missile expected to begin Monday morning.

The crucial test, known as the wet dress rehearsal, simulates each phase of the launch without the rocket leaving the launch pad at Kennedy Space Center in Florida.

This process involves loading super-cold propellant, running a full countdown simulating launch, resetting the countdown clock, and emptying the rocket tanks.

The results of the wet dress rehearsal will determine when the unmanned Artemis I will launch on a mission that will go beyond the Moon and return to Earth. This mission will launch NASA’s Artemis program, which is expected to return humans to the moon and land the first woman and first colored person on the lunar surface by 2025.

Three previous attempts at the April wet rehearsal were unsuccessful, ending before the rocket could be fully loaded with propellant due to various leaks. These have since been corrected, says NASA.

The NASA team rolled the 98-meter-tall Artemis I rocket stack, including the Space Launch System and the Orion spacecraft, back to the launch pad at Kennedy Space Center in Florida on June 6.

Wet Dress Rehearsal: What to Expect

The wet dress rehearsal began Saturday at 5 p.m. ET with a “call to the stations” — when all teams associated with the mission arrive at their consoles and report that they are ready to begin testing and begin a two-day countdown.

Preparations over the weekend will prepare the Artemis team to begin loading propellant into the rocket’s core and upper stages.

There is currently a live view of the rocket on the NASA website with intermittent commentary.

Refueling is currently suspended due to an issue identified with the backup gaseous nitrogen supply. The launch team has already replaced the valve causing the problem. To ensure the backup supply was working as expected, it was swapped out as the primary supply for today’s test.

The hold is scheduled to be lifted at 9:20 am ET.

A two-hour testing window begins later, with the Artemis team targeting the first countdown at 4:30 p.m. ET. due to the tank delay.

NASA subjects the Artemis lunar rocket to crucial steps before launch

First, team members counts down to 33 seconds before starting and then stops the cycle. The clock is reset; then the countdown resumes and runs until about 10 seconds before a start would occur.

“During testing, the team may await the countdown as needed to verify conditions before resuming the countdown, or extend this beyond the testing window as needed and resourced,” an update on NASA’s website reads.

The previous wet dress rehearsal attempts have already achieved many goals to prepare the rocket for launch, said Charlie Blackwell-Thompson, Artemis launch director for NASA’s Exploration Ground Systems program, during a news conference Wednesday.

“We hope to finish them this time and survive the cryogenic loads along with the number of terminals,” she said. “Our team is ready to go and we look forward to returning to this test.”

The mission team is evaluating possible launch windows to send Artemis I on its journey to the Moon in late summer: August 23-August 29, September 2-September 6 and beyond.

Once the Artemis rocket stack has completed its wet dress rehearsal, it will taxi back to the Space Center’s vehicle assembly building to await launch day.

The painstaking testing of new systems before a launch has a long history, and the Artemis team faces similar experiences as the Apollo and shuttle-era teams, including multiple test attempts and delays.

“There is not a single person on the team who shies away from the responsibility that we ourselves and our contractors must manage and deliver and deliver means to achieve these flight test goals for (Artemis I) and the goals of the Artemis I program,” said Jim Free, deputy administrator of NASA’s Exploration Systems Development Mission Directorate, during last week’s press briefing.