After a very long day of work, the Artemis team has earned a well-deserved chance to appreciate a job well done following the completion of its fourth wet dress rehearsal. NASA administrators announced during the post-wet dress teleconference that although the latest exercise wasn’t without a few hiccups, all of the critical targets had been met.

The wet dress rehearsal ended at 6:37 p.m. CDT at T-29 seconds in the countdown rather than T-9, as originally planned. This test marked the first time the team fully loaded all the Space Launch System (SLS) rocket’s propellant tanks and proceeded into the terminal launch countdown.

During propellant loading operations earlier in the day, launch controllers found a hydrogen leak in the quick disconnect that attaches an umbilical from the tail service mast on the mobile launcher to the SLS core stage.

After troubleshooting measures failed to correct the issue, launch controllers developed a plan to mask data associated with the leak that would trigger a hold by the launch computer in a real launch day scenario.

This allowed them to proceed with the countdown: although the time needed to develop the new plan extended the hold time, the team was able to resume with the final 10 minutes of the countdown, called terminal count.

The leak had no bearing on the crews’ ability to fully load the rocket with cryogenic liquid hydrogen propellant, proving its ability to be safely loaded and to make sure launch day procedures would go smoothly.

During the terminal count, the teams performed several critical operations necessary for launch including switching control from the ground launch sequencer to the automated launch sequencer controlled by the rocket’s flight software, an important benchmark for the team.

Although the count ended approximately 20 seconds earlier than planned, NASA officials deemed the rehearsal an overall success.

“It was a long day for the team but I think it was a very successful day,” said Launch Director Charlie Blackwell-Thompson. “We accomplished a majority of the objectives that we had not completed in the prior wet dress.”

“We got through the cryo load of both the core stage and the upper stage, we got through terminal count–these are really important things that we wanted to see. I try to remind people, you know, we talked about being pieces of a puzzle and a delicate dance–we got through the dance and now we’re looking at the pieces of the puzzle to decide what are the pieces that we didn’t get,” said Tom Whitmeyer, Deputy Associate Administrator for Common Exploration Systems Development at NASA Headquarters.

“We also got a lot of pieces of the puzzle put together and we have a pretty good idea of what the puzzle looks like at this point.”

Blackwell-Thomas expressed pride in the efforts of the team, noting that the lessons learned from the earlier attempts were incorporated into their approach yesterday. In turn, she explained, the lessons learned from the most recent attempt will be used going forward.

Ground teams at Kennedy Space Center will spend the next few days preparing the Artemis 1 stack and mobile launch platform for transport from Launch Pad 39B back to the Vehicle Assembly Building (VAB), where NASA technicians will analyze data gathered from the rehearsal exercise.

The wet dress was the final major milestone that Artemis 1 needed to complete prior to launch. Despite its overall success, the official launch date has not yet been set and will be announced in the near future following data analysis and evaluation.