Artemis II draws closer to WDR
NASA’s SLS (Space Launch System) rolled out on January 17th to LC-39B (Launch Complex 39B) and is now preparing to conduct the WDR ahead of Artemis II, the first crewed lunar mission in more than 50 years. The WDR (Wet Dress Rehearsal) will involve running through a simulated launch countdown, testing all the launch activities, including power-up, mechanical connections, and fueling procedures.
Update: NASA has announced the WDR is scheduled for a simulated T0 of 9pm EST on January 31st. This means the start time will be approximately 8pm EST of January 29th.
WDR - The final step
The WDR (Wet Dress Rehearsal) marks the final stepping stone before NASA can go ahead and select a launch date for the Artemis II mission. This test involves running through every launch preparation, from the moment that controllers sit down at the console to a few seconds before launch, testing all the mechanical and electrical interfaces, battery charging, vehicle state, pressurization, and most importantly, fueling and detanking procedures.
The WDR starts at L-49 hours, when teams get on console, and comprises 2 runs:
First run: the first run includes all the operations down to L-1m30s, when the core stage switches to internal power. At this point, the countdown clock will hold for 3 minutes before starting again, going down until L-33s, when the ALS (Automatic Launch Sequencer) takes control of the countdown. It’s NASA-designed software that takes control of the countdown and runs it autonomously, conducting thousands of checks to verify that the right conditions are met ahead of liftoff.
Second run: the second run includes recycling back to L-10 minutes and going down until 30 seconds before liftoff.
This crucial test is meant to test all of the rocket and capsule components needed for launch, as well as the ground components and tanks. There are 2 main concerns NASA has for this WDR: the first one is the oxygen/hydrogen loading phase, since it caused widespread issues during Artemis I’s WDR in 2022 due to temperature issues and propellant leaks; the second one is the unwanted presence of gaseous nitrogen between Orion’s crew module and the launch abort system hatches.
However, both of these issues are known in advance, and NASA teams have taken precautions and effective measures against them; still, it is worth monitoring the situation to validate these changes.
Pre-launch work and activities
Following the rollout, teams immediately positioned the rocket at the pad, connecting all of the umbilicals and connections needed.
Then, in the following days, the crew had a walkdown at the pad, where they familiarized themselves with the environment they will face on launch day.
Technicians connected purge lines to keep the cavities of the rocket and spacecraft in the right condition, enabled communications with the Launch Control Center, and performed swing tests of the crew access arm, the mobile arm that connects the service structure to the capsule.
On January 22nd, the Emergency Egress System (EES) was tested: this system sends a series of baskets at high speeds traveling on a wire connecting the launch platform and the ground so that crew and teams can evacuate quickly and safely in the case of an emergency. NASA stated that the baskets stopped short of their planned touchdown zone on the ground during the test, and engineers have adjusted the brakes to ensure full descent and safety.
On the same day, teams began a multi-day testing campaign of radio frequency communications with the Eastern Range, while over the weekend, technicians loaded hydrazine onto the SRBs (Solid Rocket Boosters) for the reaction control system (it controls the orientation of the boosters and steers them away from the rocket after separation), checked out the 4 RS-25 engines, pressurized a COPV used for the spacecraft’s propulsion system, and loaded final items in Orion (including tablets, medical kits, and science investigations). The capsule was also subject to pyrotechnics work of the launch abort system.
Before the WDR, technicians and engineers still have to load final items in Orion, thoroughly check systems, and take samples of the potable water system to ensure the water is drinkable, since previous samples showed a higher-than-expected concentration of total organic carbon.
Weather permitting, NASA is on track for a WDR in the next few days, and if all goes well, then we might see Artemis II liftoff shortly afterwards: the launch windows for February are on the 6th, 7th, 8th, 10th, and 11th.
Crew getting ready
The Artemis II crew. Credit: NASA
Meanwhile, the crew of 4 – Reid Wiseman, Victor Glover, Christina Koch, and Jeremy Hansen – is preparing for their historic mission.
This crew - in the roles of commander, pilot, and mission specialists, respectively - will be the first to go back to cislunar space since 1972, as well as going further than any human has ever gone, breaking several records for cislunar space (first woman, first person of color, and first Canadian).
While training is over, the crew started their 2-week quarantine period on January 24th at the Johnson Space Center in Houston; quarantine is needed to avoid a member getting sick or hurt, and it is performed ahead of the mission.
Once a launch date is confirmed, the crew is scheduled to go to the Kennedy Space Center in Florida, an estimated 6 days before launch.
References
Launch Pad Preparations Progress Ahead of Artemis II Wet Dress Rehearsal - NASA
The Launch Pad (@TLPN_Official) / Posts / X
NASA Artemis (@NASAArtemis) / Posts / X
