The fourth attempt at a final pre-launch test began on Saturday and the rocket’s fuel tanks were filled on Monday.
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.
Wet dress rehearsal steps
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 saw the Artemis team begin loading propellant into the rocket’s core and upper stages on Monday morning.
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. In order to ensure that the backup power supply works as expected, it was replaced as the main power supply for the 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 center stage before moving to the upper stage of the rocket. Venting was visible from the rocket throughout the process.
The main floor was mostly full and the team was filling the upper floor when several issues arose just after 2 p.m. ET.
The team discovered a hydrogen leak at a quick disconnect line for the core stage. Their first option didn’t work and they looked into options for sealing the leak.
Something from the flare, where excess liquid hydrogen from the rocket is burned with propane flames, caused a small grass fire burning towards a dirt road. The crew watched the grass fire and expected the fire to go out when it reached the dirt road.
The test exceeded a planned 30-minute wait, which was extended as engineers attempted to work out solutions for the hydrogen leak.
The Artemis team decided to do a countdown, while masking the hydrogen leak issue, ‘to further test for today’s wetsuit repeat’, according to a tweet. of NASA Exploration Ground Systems.
The 10-minute countdown began at 7:28 p.m. ET.
Typically, there are two countdowns during the wetsuit rehearsal. First, team members typically count down to 33 seconds before launch, then stop the cycle. The clock is reset, then the countdown resumes and lasts until approximately nine seconds before a launch occurs.
Monday’s abbreviated countdown ended prematurely with 29 seconds remaining on the countdown clock. A flag from the SLS rocket computer triggered the cutoff, but the exact flag was not shared. Ahead of the countdown, the team said that if the computers involved in the countdown detect the hydrogen leak, it could look like a check engine light that forces the countdown to stop prematurely.
Once the countdown stopped, the Artemis team worked to ensure the vehicle was safe.
Charlie Blackwell-Thompson, Artemis launch director for NASA’s Exploration Ground Systems program, said it was “definitely a good day for us” after hitting several milestones outlined in the wetsuit goals, such as Completely fill the rocket and pass a countdown.
The next steps will be to assess all the data collected during the test, including any issues, and develop a plan moving forward, she said.
Previous wetsuit rehearsal attempts have already achieved many goals in preparing the rocket for launch, Blackwell-Thompson said.
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.