The fourth attempt at a final pre-launch test began on Saturday, with refueling of the rocket due to begin Monday morning.
The crucial test, known as the wet dress rehearsal, simulates every stage of the launch without the rocket leaving the launch pad at Kennedy Space Center in Florida.
This process includes loading supercold propellant, performing a full launch-simulating countdown, resetting the countdown clock, and draining the rocket’s fuel tanks.
The results of the dress rehearsal will determine when the uncrewed Artemis I embarks on a mission that will go beyond the moon and back 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 person of color on the lunar surface by 2025.
Three previous attempts at a wet dress rehearsal in April failed, ending before the rocket could be fully loaded with propellant due to various leaks. These have since been corrected, according to NASA.
The NASA team brought the 322-foot-tall (98-meter-tall) Artemis I rocket stack, including the Space Launch System and Orion spacecraft, back to the launch pad at Kennedy Space Center in Florida June 6.
Rehearsal in a wet suit: what to expect
The wetsuit rehearsal began at 5 p.m. ET on Saturday with a “call to the stations” – when all teams associated with the mission arrive at their consoles and signal that they are ready for the test to begin and launch a two-day countdown.
Preparations for the weekend will set up the Artemis team to begin loading propellant into the rocket’s core and upper stages.
The tanking was on hold Monday morning due to an identified problem with the backup nitrogen gas supply. The launch team replaced the valve causing the problem. To ensure that the backup power supply works as expected, it was replaced as the main power supply for today’s test.
The hold was lifted at 9:28 a.m. ET. Liquid oxygen, cooled to minus 297 degrees Fahrenheit (minus 182 degrees Celsius), and liquid hydrogen will fill the tanks. Venting may be visible as the reservoirs fill up.
A two-hour test window will begin later, with the Artemis team targeting the first countdown at 4:38 p.m. ET. due to the tanking delay.
First, the team members will go through a countdown up to 33 seconds before launch, then stop the cycle. The clock will be reset; then the countdown will resume and run until approximately 10 seconds before a launch occurs.
“During the test, the team may hold out during the countdown if necessary to verify conditions before resuming the countdown, or extend beyond the test window, if necessary and resources permitting. “, according to an update on NASA’s website.
Previous wetsuit rehearsal attempts have already achieved many goals in preparing the rocket for launch, Charlie Blackwell-Thompson, Artemis launch director for NASA’s Exploration Ground Systems program, told a conference at press on Wednesday.
“We hope to complete them this time around and get through the cryogenic loading operations as well as the terminal count,” she said. “Our team is ready to go, and we can’t wait to get back to this test.”
After the Artemis rocket stack completes its dress rehearsal, it will return to the Space Center’s Vehicle Assembly Building to await launch day.
There’s a long history behind the arduous testing of new systems before a launch, and the Artemis team faces experiences similar to those of the Apollo and shuttle-era teams, including multiple test attempts and delays.
“There is not a single person on the team who avoids the responsibility that we have to manage ourselves and our contractors and deliver, and delivering means meeting those flight test goals for (Artemis I ), and achieve the goals of the Artemis I program,” Jim Free, associate administrator for NASA’s Exploration Systems Development Missions Directorate, said during last week’s press conference.