The Artemis I wet dress rehearsal ended yesterday (June 20, 2022) at 7:37 p.m. EDT (4:37 p.m. EDT) at T-29 seconds in the countdown. This test marked the first time the team fully loaded all the Space Launch System rocket’s propellant tanks and proceeded into the terminal launch countdown, when many critical activities occur in rapid succession.
During propellant loading operations earlier in the day, launch controllers encountered a hydrogen leak in the quick disconnect that attaches an umbilical from the tail service mast on the mobile launcher to the rocket’s core stage. The team attempted to fix the leak by warming the quick disconnect and then chilling it back down to realign a seal, but their efforts did not fix the issue.
Launch controllers then developed a plan to mask data associated with the leak that would trigger a hold by the ground launch sequencer, or launch computer, in a real launch day scenario, to allow them to get as far into the countdown as possible. The time required to develop the plan required extended hold time during the countdown activities, but they were able to resume with the final 10 minutes of the countdown, called terminal count. During the terminal count, the teams performed several critical operations that must be accomplished for launch including switching control from the ground launch sequencer to the automated launch sequencer controlled by the rocket’s flight software, and important step that the team wanted to accomplish.
This second Artemis I wet dress rehearsal kicked off on June 18, 2022. After the launch team arrived at their stations inside the Launch Control Center at NASA’s Kennedy Space Center in Florida at approximately 5 p.m. EDT to begin the wet dress rehearsal test for NASA’s Artemis I mission. The countdown began 30 minutes later at 5:30 p.m. or L-45 hours, 10 minutes before the initial target T-0 of 2:40 p.m. on Monday, June 20.
Overnight from June 18th to the 19th, engineers powered up the Orion spacecraft and the Space Launch System’s core stage. Teams also configured several systems on the ground, rocket, and spacecraft and performed activities to prepare umbilicals that connect the rocket and spacecraft to the mobile launcher and are used to provide power, communications, coolant, and propellant.
On the morning of June 20, the launch control team began chill down operations and resumed the countdown clock ahead of flowing super cold liquid oxygen (LOX) into the core stage tank. The T-0 time for today’s test is now 4:38 p.m. EDT for the first of the two terminal count runs for the wet dress rehearsal.
The process for filling the core stage tank begins with the chill down, or cooling, of the propellant lines to load the liquid oxygen and liquid hydrogen in preparation for tanking. The team will slowly fill liquid oxygen into the core stage tank with the fast fill beginning soon after. Teams will then proceed to slowly fill the core stage’s liquid hydrogen tank followed by fast fill.