The mission team plans to start fueling the 322-foot-tall (98-meter-tall) Artemis I rocket stack, including NASA’s Space Launch System and Orion spacecraft, on Thursday.
The test, known as the wet dress rehearsal, has been adjusted in response to an issue encountered during preparations for the third attempt that took place over the weekend. Engineers identified a helium check valve that wasn’t functioning. The valve is difficult to reach while the rocket sits on the launchpad, but it can be replaced or fixed later. The modified version of the wet dress rehearsal is necessary to ensure the safety of the rocket’s flight hardware.
Helium is used to purge the engine before loading super cold propellant — the wet in wet dress rehearsal — during fueling. Check valves allow gas or liquid to flow in one direction to prevent backflow. In this case, the part that isn’t working is about 3 inches long and keeps helium from flowing back out of the rocket.
When tanking of the rocket’s core stage starts Thursday, the modified test will take the strain off of the valve and the upper rocket stage with minimal propellant operations. Previously, the team had planned to fully fuel the core and upper stages of the rocket, but the valve issue prevents that step from taking place during this test.
The results of this rehearsal will determine whether any more tests need to take place before launch.
“I’m very confident that we’re going to have a good test on Thursday with the modified procedures,” said John Blevins, SLS chief engineer at NASA’s Marshall Space Flight Center in Huntsville, Alabama, during a Monday news conference. “I can’t say I’m pleased that we have a broken part, but I am glad that we caught it when we did before we get into any operations that would be compromised by having a broken part. That’s why we do these thorough tests.”
The wet dress rehearsal simulates every stage of launch without the rocket actually leaving the launchpad. This includes powering on the SLS rocket and Orion spacecraft, loading supercold propellant into the rocket’s tanks, going through a full countdown simulating launch, resetting the countdown clock and draining the rocket tanks.
It will begin Tuesday around 5 p.m. ET with the call to stations, which is a check-in with every team associated with a launch to say that the test has begun.
Once this test is complete, the Artemis I rocket will be rolled back into the Vehicle Assembly Building at Kennedy Space Center in Florida where teams can analyze the valve and replace it if necessary.
The previous attempts at the wet dress rehearsal have already provided valuable insight for the team, officials said, even as they have worked through various issues.
“We have completed a lot of the test requirements that we needed to get out of wet dress activity,” said Tom Whitmeyer, deputy associate administrator for exploration systems development at NASA Headquarters, during a news conference Monday. “We have a few more that we’re going to get to on Thursday. The mega moon rocket is in great shape and we’re treating it very carefully.”
While the exact issues identified during the test attempts weren’t anticipated, it’s part of the process when testing out a new rocket.
“Any new rocket that comes forward in a new program like this kind of goes through these updates and understanding how the rocket is performing,” Whitmeyer said. “And that’s the type of thing that we’re going through right now.”
“I can say that these will probably not be the last challenges we’ll encounter,” said Mike Sarafin, Artemis mission manager at NASA Headquarters, during the conference. “But I’m confident that we have the right team in place and the ability to rally around those problems and overcome them is something that that we take pride in.”
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.
The current launch window possibilities include June 6 through June 16, June 29 through July 17 and July 26 through August 9, Sarafin said.
Correction: An earlier version of this story misstated the number of attempts for the Artemis wet dress rehearsal test.
