NASA’s Space Launch System (SLS) rocket with the Orion spacecraft atop arrived at Launch Pad 39B at the agency’s Kennedy Space Center in Florida Friday in preparation for a final test before its Artemis I Moon mission.
Stacked on the mobile launcher and mounted on the crawler-transporter for a journey from the Vehicle Assembly Building to Launch Pad 39B, it took 10-hours and 28 minutes for SLS and Orion to reach the launch pad four miles away. The trip began at 5:47 p.m. Thursday, March 17, and the 322-foot tall, 3.5-million-pound rocket and spacecraft arrived at the pad at 4:15 a.m. on March 18.
Engineers will conduct the final test, known as the wet dress rehearsal, 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. The 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 31,82,260 Liters (700,000 gallons) of cryogenic, or super chill, propellants including liquid hydrogen(LH2) and liquid oxygen(LOX) into the 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.
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.
Several days after the wet dress rehearsal, the integrated rocket and spacecraft will be rolled back to the Vehicle Assembly Building (VAB). In the VAB, technicians will extend platforms to reestablish access to numerous parts of the rocket and spacecraft. They will remove sensors specifically used for monitoring during the wet dress rehearsal, charge Orion and other system batteries, stow late-load cargo into Orion, and run final checkouts on various elements, among other tasks. Orion and SLS will roll to the launch pad for a final time about a week before launch.
NASA will review data from the rehearsal before setting a specific target launch date for the Artemis I launch. The first in a series of increasingly complex missions, Artemis I will provide a foundation for human deep space exploration and demonstrate our commitment and capability to extend human existence to the Moon and beyond prior to the first flight with a crew on Artemis II.