NASA’s return to the Moon rests on the powerful shoulders of its huge Moon rocket, the Space Launch System (SLS). Over the last few months, the agency has been conducting the last crucial series of tests before its launch, however, not without issues. Now, it has passed a crucial milestone, with the Artemis team successfully fueling the rocket, despite a leak, during its latest wet rehearsal.  

The first wet dress rehearsal was conducted in early April but a series of problems led to NASA postponing the rehearsal and the subsequent launch that was originally scheduled for this month.

The huge rocket was rolled back to the launch pad (you can watch it live on its launchpad here) and on June 20 the wet dress rehearsal began anew. Wet rehearsals are simulations of every step of a launch, including fueling the rocket and the countdown going down to 10 seconds before lift-off, without actual ignition.

Wet is the keyword there. The rocket, which weighs a whopping 2.6 million kilograms (5.75 million pounds) when fuelled, was loaded with almost 3.2 million liters (700,000 gallons) of cryogenic propellant, the first time it has been fully fueled. The test was then conducted as a scrub, the name for an aborted launch, with the countdown getting down to 29 seconds before lift-off before it was ended.

While this wet dress rehearsal has shown how far the whole operation has come, it still encountered some snags. Pre-launch, controllers spotted a hydrogen leak in the system that disconnects the umbilical – one of the several connections between the rocket and the launchpad. Attempts to fix the leak were not successful so the team bypassed it, deciding to end the rehearsal slightly early at T-29 rather than at T-9.3 as planned. In reality, this would have likely scrubbed a real launch.

“That was a big milestone for us,” launch director Charlie Blackwell-Thompson said of fueling the vehicle during the live coverage on NASA TV. “Definitely a good day for us and a very exciting day as well.” 

This was the final milestone SLS, also known as Artemis I, needed to complete before its first launch, which will see an uncrewed Orion capsule travel on a month-long journey to the Moon and back.

An announcement of the launch date should be coming soon, but it will likely be no earlier than late August 2022.