The fourth attempt at a final pre-launch test began on Saturday, with the rocket expected to refuel Monday morning.
The pivotal test, known as the wet dress rehearsal, simulates each launch phase without the rocket leaving the launch pad at Kennedy Space Center in Florida.
This process involves loading super-cold propellant, going through a full launch simulating countdown, 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 beyond the moon and return to Earth. This mission will kick off 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 the wet-dress rehearsal in April were unsuccessful and ended before the rocket could be fully charged with propellant due to several leaks. These have since been corrected, NASA says.
The NASA team rolled the 98-foot-tall Artemis I rocket stack, including the Space Launch System and the Orion spacecraft, back to the launch pad at the Kennedy Space Center in Florida on June 6.
Rehearsal steps for wet clothes
The wet dress rehearsal kicked off Saturday at 5 p.m. ET with a “call to stations” — when all teams involved in the mission arrive at their consoles and report that they are ready to begin testing and kick-off a two-day event. countdown.
During weekend preparations, the Artemis team will begin loading propellant into the rocket’s core and upper stages.
Refueling was halted Monday morning due to a problem with the back-up supply of gaseous nitrogen. The launch team replaced the valve that caused the problem. To ensure that the backup power supply works as expected, it was swapped out as the primary 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 were used to fill the nuclear stage before continuing to the top stage of the rocket. Venting has been visible from the rocket throughout the process.
The core stage is mostly filled and the team was busy filling the top stage when several issues arose just after 2pm ET.
The team discovered a hydrogen leak during a rapid disconnect before the core phase and is trying to fix it. Their first option didn’t work and they are looking for another way to fix the leak.
Something from the flare stack, where excess liquid hydrogen from the rocket burned us down with propane flames, has set off a small grass fire that burns toward a dirt road. The team is monitoring the grass fire and don’t expect it to become a problem as the fire is likely to be extinguished when it reaches the dirt road.
After successfully solving a pressure problem, liquid oxygen returns to the upper stage. Currently, three of the missile’s four tanks are filled.
The test is now in a scheduled 30-minute wait, giving the launch team a chance to catch up.
countdown
A two-hour test period will begin later, with the Artemis team targeting the first countdown at 4:28 p.m. ET, but that will likely be moved due to delays.
First, team members will count down to 33 seconds to launch and then stop the cycle. The clock is reset; then the countdown resumes and takes up to approximately 10 seconds for a launch to occur.
“During the test, the team can hold the countdown if necessary to monitor conditions before resuming the countdown, or if necessary and resources permit, go beyond the test window,” according to an update on NASA’s website.
Previous wet rehearsals have already accomplished many goals to prepare the rocket for launch, Charlie Blackwell-Thompson, Artemis launch director for NASA’s Exploration Ground Systems Program, said at a news conference on Wednesday.
“We hope to complete them this time and get through the cryogenic loading operations along with the number of terminals,” she said. “Our team is ready to go and we look forward to returning to this test.”
Once the Artemis rocket stack has completed its wet dress rehearsal, it will roll back to the space center vehicle assembly building to await launch day.
There is a long history of arduous testing of new systems before launch, and the Artemis team faces similar experiences 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 would shy away from the responsibility we have to manage and deliver to ourselves and our contractors, and delivering means meeting those flight test targets for (Artemis I) and meeting the objectives of the Artemis I program,” said Jim Free, associate administrator for NASA’s Exploration Systems Development Mission Directorate, during last week’s press conference.