The crucial test, known as the wet dress rehearsal, simulates every stage of launch without the rocket leaving the launchpad. This process includes loading propellant, going through a full countdown simulating launch, resetting the countdown clock and draining the rocket tanks.
The team was able to load supercold propellant into the SLS rocket’s core stage tanks but “encountered a liquid hydrogen leak on the tail service mast umbilical that prevented the team from completing the test,” according to the agency.
“After troubleshooting it, the team decided to knock it off for the day because when you have hydrogen leaks, and you have ambient oxygen out there, you only need an ignition source to close the fire triangle. So it was a flammability risk,” Mike Sarafin, Artemis mission manager at NASA headquarters, said during a Friday news conference.
Technicians collected data, drained the tanks and ensured that the rocket remained safe and stable. Despite the leak, the team was able to work through a number of critical test items during the third attempt.
“The mega moon rocket is fine,” Sarafin said. “All the issues that we’re encountering are procedural and lessons learned.”
Now, the test team continues to assess how to address the leak. Troubleshooting began Friday morning.
The team “will look at these particular areas that we think could be the issue, how we get access to them” and determine a pathway forward, said Charlie Blackwell-Thompson, Artemis launch director for NASA’s Exploration Ground Systems program, during a Friday news conference.
In the meantime, the team is getting ready for the next potential opportunity at another wet dress rehearsal attempt on April 21, the earliest time the team is comfortable with, Sarafin said. The Artemis team is working closely with SpaceX because the Crew-4 launch is expected to take place at a nearby launchpad on April 23.
Sarafin did not disclose the exact plan for keeping the run-through on track, given that only 24 hours have passed since the leak, but he said the team is looking into options that are “readily accessible.”
“We hope that here’s something that is fairly straightforward and needs to be adjusted or is easily resolved, and we can do that at the pad and do it in fairly short order,” Sarafin said. “And then there are a couple of more invasive options, and we’ve got to weigh those against a whole host of considerations that include putting additional stress on the vehicle.”
The longer the rocket remains on the launchpad, the more it’s subjected to wind and other stressors while exposed to the elements — not to mention the strain induced by repeated tests. That could determine when the stack will be rolled back into the Vehicle Assembly Building at the space center.
Testing ambitious missions
When asked if it’s possible for Artemis I to launch without completing certain aspects of a full test, the team said it would have to reach an acceptable level of risk. But the ground and flight test programs are not complete, so the team hasn’t reached that consideration yet, Sarafin said.
The point of the wet dress rehearsal is to learn about issues that can be corrected before being forced to abort a launch attempt, and it’s something that the Apollo and shuttle programs faced as well, Blackwell-Thompson said.
There were about five or six fuelings, or wet dress rehearsals, of the first shuttle before launch, she said. And the shuttle only had a single stage, whereas the SLS rocket has a core and an upper stage that must be fueled with supercold propellant, which makes the process even more complex.
Sarafin said the team occasionally speaks with personnel who worked on the previous programs, comparing the challenges of physics, fluid dynamics, thermodynamics, supercold temperatures, structural stresses and flammability hazards.
“History has shown it’s been a challenge for pretty much anybody that’s done anything of this magnitude,” Sarafin said.
The results of the wet dress rehearsal will determine when the uncrewed Artemis I will launch on a mission that goes beyond the moon and returns to Earth. This mission will kick off NASA’s Artemis program, which is expected to return humans to the moon and land the first woman and the first person of color on the lunar surface by 2025.
“But there’s no doubt in my mind that we’ll finish the test campaign and we will be ready to go fly,” Blackwell-Thompson added.