Artemis I Moon Rocket Rolls to Launch Pad for Wet Dress Rehearsal

At approximately 12:10 a.m. EDT on June 6, NASA’s Artemis I Moon rocket began its journey from Kennedy Space Center’s Vehicle Assembly Building (VAB). Poised atop its crawler transporter, the Space Launch System rocket and Orion spacecraft made the 4-mile journey to launch pad 39B to undergo the next wet dress rehearsal test attempt.

The rehearsal will run the Artemis I launch team through operations to load propellant into the rocket’s tanks, conduct a full launch countdown, demonstrate the ability to recycle the countdown clock, and also drain the tanks to give them an opportunity to practice the timelines and procedures they will use for launch.

During the approximately two-day test, teams will start by activating the facilities needed for launch and formally beginning the countdown sequence. Team will staff the Launch Control Center at Kennedy and connect with staff in the Mission Control Center at NASA’s Johnson Space Center in Houston, the Space Force Eastern Range, and the SLS Engineering Support Center at the agency’s Marshall Space Flight Center in Huntsville, Alabama. Launch controllers will power on different rocket and spacecraft systems, along with ground support equipment.

Teams will then load more than 700,000 gallons of cryogenic, or super cold, propellants including liquid hydrogen and liquid oxygen into the Artemis I Moon rocket at the launch pad on the mobile launcher according to the detailed timeline they will use on the actual launch day. They will practice every phase of the countdown, including weather briefings, pre-planned holds in the countdown, conditioning and replenishing the propellants as needed, and validation checks.

Following a previous Artemis I Moon Rocket wet dress rehearsal, engineers replaced a faulty helium check valve on the interim cryogenic propulsion stage that was identified after the second wet dress rehearsal attempt. Engineers have inspected the valve and found a small piece of rubber that prevented the valve from sealing correctly. Teams are looking at possible sources of the debris, but did not see any issues with the valve itself.

Engineers also performed tests to address a hydrogen leak on one of two tail service mast umbilicals between the mobile launcher and the rocket. These umbilicals provide liquid oxygen and liquid hydrogen propellants, as well as electrical connections, from the mobile launcher to the rocket’s core stage during the launch countdown. Teams conducted leak checks on all the joints and tightened several flange bolts, or fasteners that act as a washer to increase the compression strength, that can loosen over time and were the most likely source of the leak. Teams re-tightened the flange bolts on the liquid hydrogen, liquid oxygen, and core stage intertank umbilicals. Engineers have not detected leaks in subsequent testing at ambient air temperature, and will continue to monitor for leaks when loading the super cold propellants at the launch pad.

During the wet dress rehearsal, once launch controllers reach the point just before the rocket’s RS-25 engines will ignite on launch day, they will recycle back to the T-10 minute point, and then resume the countdown once more after a hold. The team will then deliberately halt the countdown at about 10 seconds before the simulated liftoff to demonstrate stopping a launch and draining the propellants from the rocket. Sometimes called a “scrub,” launch controllers may decide not to proceed with launch if a technical or weather issue arises during or prior to the countdown, so demonstrating the ability to remove propellants will ensure teams are prepared for various launch day scenarios.

(Source: NASA. Image from file)