Four astronauts have to wait a little longer before starting their historic mission to the moon.
Their rocket, that Space Launch System (SLS), rolled back from Launch Complex-39B (LC-39B) to the Vehicle Assembly Building (VAB) at NASA’s Kennedy Space Center (KSC) in Florida today (February 25). It is now safely tucked away inside VAB’s High Bay 3, where engineers will begin work on troubleshooting the rocket’s upper stage, in an area inaccessible out at the pad.
SLS’s helium problem was discovered overnight from February 20 to February 21, a day after the completion of a “wet dress rehearsal”, in which the rocket was fully fueled and run through a simulated launch countdown. It was the second such fuel test for the SLS, but the first to be considered a success. The first ended earlier than planned on February 2 after a leak of liquid hydrogen was detected under the SLS core stage propellant, prompting the mission clock to reverse an automatic abort command at T-5:15.
“The team was unable to get helium flow through the vehicle” during a routine purge and repressurization procedure on the SLS’s Interim Cryogenic Propulsion Stage, NASA Administrator Jared Isaacman said in a post from February 21 on X.
Helium is stored in tanks connected to the ICPS, which are only accessible while the rocket is inside the VAB, forcing NASA’s decision to roll back the rocket and delay the launch. In his X post, Isaacman pointed out that the problem could have multiple possible causes, and that rolling back would allow engineers to figure out what went wrong.
Artemis 1The 2022 launch campaign also had problems – such as a persistent hydrogen leak. The unmanned mission to lunar orbit required three trips between the VAB and the LC-39B over the course of several months before NASA was able to clear the SLS for launch, which it finally did in November of that year. Now, the agency hopes to avoid a repeat of the repeat, and Isaacman pointed out in his post that “corrective actions were taken to minimize a repeat of Artemis 2.”
Artemis 2 launch director Charlie Blackwell-Thompson gave the order to begin the rollback of the SLS this morning at 09:28 EST (1428 GMT), with first movement about 10 minutes later, according to a NASA update. The 322-foot-tall (98.15-meter) SLS rocket then made its way down the gentle slope of LC-39B atop NASA’s massive Crawler-Transporter 2 vehicle, beginning the 4-mile (6.4-kilometer) journey back to the VAB.
The ring boat was trucking along the Alabama River cobbled road between the pad and the VAB at about 1.6 mph, crushing the rocks under its treads into sand under the weight of the rocket and carrier.
The Artemis 2 stack reached VAB at approx. 8 p.m. EST (0100 GMT on Feb. 26), according to NASA officials, meaning today’s walk took 10.5 hours. Now that it’s safely back inside the VAB, NASA hopes to diagnose and repair the rocket’s upper stage problems in time to roll SLS back to LC-39B and, presumably, complete a third wet dress rehearsal before Artemis 2’s early April launch window, which opens April 1, with other opportunities each day from April 3 to 6.
