The fourth attempt at the final pre-launch test began on Saturday and the missile tanks filled up on Monday.
The critical test, known as wet wear training, simulates each stage of the launch without the rocket leaving the launch pad at the Kennedy Space Center in Florida.
This process includes loading ultra-cooled propellants, performing a complete countdown simulating a launch, resetting the countdown clock, and draining the missile tanks.
The results of training in wet clothes will determine when Artemis I will embark on a mission 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 people of color on the moon by 2025.
Three previous attempts at rehearsal in April were unsuccessful, and ended before the missile could be fully loaded with fuel due to various leaks. NASA says these errors have since been corrected.
The NASA team rolls a 322-foot (98 m) stack of Artemis I rockets, including the Space Launch System and Orion spacecraft, to the launch pad at Kennedy Space Center in Florida on June 6.
Wet rehearsal steps
The rehearsal began at 5 p.m. ET on Saturday with a “Call to Stations” — when all teams associated with the mission arrive at their consoles and report that they are ready to begin testing and a two-day countdown begins.
Preparations over the weekend prepared the Artemis team to begin loading propellant into the rocket’s core and upper stages on Monday morning.
The tanks were suspended Monday morning due to an identified problem with the backup supply of gaseous nitrogen. The launch team replaced the valve that was causing the problem. In order to ensure that the backup source is working as expected, it has been replaced as the primary supply for the test.
The comment 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 core stage before moving to the upper stage of the rocket. The vent was visible from the missile throughout the operation.
The base stage was mostly filled and the team was filling the upper stage when several issues occurred after 2pm ET.
The team detected a hydrogen leak in a rapid core-stage separation line. Their first option didn’t work out and they studied it Options to close the leak.
Something from the glow pile, where excess liquid hydrogen from the rocket is being burned with a propane flame, caused a small fire in the grass toward a dirt road. The team monitored the grass fire and expected the fire to break out when it reached the dirt road.
The test exceeded the planned 30-minute waiting period, which was extended as engineers tried to work on solutions to the hydrogen leak.
The Artemis team decided to go ahead with one countdown, while masking the hydrogen leak issue, “in order to move forward with our wet clothes rehearsal test today,” according to a tweet from NASA’s Earth Exploration Systems.
The 10-minute countdown began at 7:28 p.m. ET.
Usually, there are two countdowns during rehearsal. First, team members usually go through a 33-second countdown before launch, and then stop the cycle. The clock resets, then the countdown resumes again and runs until about nine seconds before the launch occurs.
Monday’s brief countdown ended prematurely with 29 seconds left on the countdown clock. A science from the SLS missile’s computer led to a cut, but the exact science has not been shared. Before the countdown, the team said that if the computers involved in the countdown sensed a hydrogen leak, it could be akin to a check engine light that forces the countdown early to stop.
Once the countdown stopped, the Artemis team worked to ensure the safety of the vehicle.
It’s “definitely a good day for us,” said Charlie Blackwell Thompson, Artemis launch manager for NASA’s Earth Exploration Systems program, after achieving several milestones set in wet-cloth goals, such as putting the entire rocket into a tank and passing the countdown.
The next steps, she said, would be to evaluate all the data collected from the test, including problems, and develop a plan moving forward.
Blackwell-Thompson said previous attempts at wet-cloth training had already completed many goals to prepare the missile for launch.
There is a long history behind the grueling testing of new systems before launch, and the Artemis team faces experiences similar to those of the Apollo and shuttle era teams, including multiple test attempts and delays.
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