NASA's Artemis 1 moon rocket will start its "wet dress rehearsal" this evening (June 18), beginning a series of crucial launch countdown tests that will last through Monday (June 20).
If all goes well, the massive Space Launch System (SLS) rocket and Orion space capsule could be headed for the moon before the end of the summer.
The wet dress rehearsal is slated to start today with a call to stations for ground teams at NASA's Kennedy Space Center (KSC) in Florida at 5 p.m. EDT (2100 GMT). Over the course of about 48 hours, the Artemis 1 team will load cryogenic fuel into the huge rocket's first and second stages. If crews don't encounter any complications tonight or tomorrow, propellant loading is scheduled to begin at 7:00 a.m. EDT (1100 GMT) on Monday.
This is the Artemis 1 stack's second time atop KSC's historic Launch Complex 39B, which first served as a pad for NASA's Apollo moon missions. Artemis 1 — the debut launch for SLS — will send an uncrewed Orion spacecraft on a month-long mission around the moon and back. If successful, NASA plans to have astronauts flying aboard the next two Artemis missions, with the space agency eyeing a lunar landing on Artemis 3 in 2025 or 2026.
The Artemis 1 stack has been standing at Pad 39B since June 6, after spending more than a month inside the Vehicle Assembly Building (VAB) at KSC. NASA's first go at an Artemis 1 wet dress rehearsal took place at the beginning of April this year. Over several days, NASA technicians attempted but failed to fuel the rocket on three separate occasions. Mechanical issues and leaks detected during cryogenic fuel transfer ultimately scrubbed April's wet dress rehearsal, and SLS was rolled back to the VAB for repairs on April 25.
If Monday morning's fuel loading occurs on schedule, NASA is targeting a simulated launch countdown at 2:40 p.m. EDT (1840 GMT). However, NASA has built in an extra two hours to account for any additional testing that needs to take place during propellant loading. Ground teams will load the SLS's core stage first, then move on to the launch vehicle's upper stage, which is called the Interim Cryogenic Propulsion Stage (ICPS).
In a call with reporters earlier this week, Charlie Blackwell-Thompson, Artemis launch director with the Exploration Ground Systems Program at KSC, said that the successful fueling of each stage will be a significant accomplishment. "Provided that we get through those milestones, then we will go into our terminal count operations," Blackwell-Thompson said.
Once the rocket is successfully fueled, mission operators plan to bring the countdown clock to T-30 before initiating its first hold. Systems will be stopped and recycled before another terminal countdown is initiated, bringing the clock all the way to T-10 seconds before initiating a final count abort.
If testing goes smoothly, SLS and Orion will spend another few days at the pad for technicians to prepare the stack for its journey back to the VAB. The Artemis 1 team will then analyze data from the wet dress, and any needed maintenance work with the rocket or mobile launch tower will be done.
Barring any further hiccups found in the vehicle or ground systems during this wet dress rehearsal, NASA officials are hoping to launch Artemis 1 as early as late August. But they won't pick a target date until all of the wet dress data have been fully analyzed and they're comfortable that the rocket is ready to fly for real.