NASA's Artemis 2 moon rocket is on the launch pad. What's next?

As the first human moon mission in decades approaches two weeks before its prime launch date, NASA has a lot to do before it can get four astronauts into space on Feb. 6.

Artemis 2 is scheduled for a 10-day mission to bring four astronauts around the moon: NASA's Reid Williams (commander), Victor Glover (pilot) and Christina Koch (mission specialist), along with Canadian Space Agency astronaut and mission specialist Jeremy Hansen.

But before the Space Launch System (SLS) rocket, its Orion spacecraft and its crew can leave Earth from Launch Pad 39B at the Kennedy Space Center (KSC) in Florida, key technical tests and a big fueling effort need to happen. It took eight months (from rollouts to launch) to bring the predecessor Artemis 1 uncrewed lunar mission into space in 2022, but NASA recently emphasized that the extra practice was beneficial.

"Why do we think that we'll be successful in Artemis 2 is, it's the lessons that we learned," said Artemis 2 launch director Charlie Blackwell-Thompson in a NASA press conference at KSC on Jan. 16, the day before SLS arrived at its launch pad. "Artemis 1 was a test flight, and we learned a lot during that campaign getting to launch," she added.

Road to launch

Artemis 2's SLS and Orion left the Vehicle Assembly Building (VAB) at KSC on Saturday at 7:01 a.m. EST (1201 GMT), reaching the pad almost exactly 12 hours later. On Jan. 16, Blackwell-Thompson said the team anticipated almost immediately connecting to (and validating connections to) ground systems, fueling systems, and the firing room. Everything will also need to be powered on.

The rocket's crew access arm, which allows the four astronauts and their support teams to reach the Orion spacecraft, will go through some test swings, she said. The emergency egress system, a basket system designed to bring the astronauts away from SLS in case of urgent issues before launch, will be configured. "Checkouts" for the pad and radio-frequency communications, along with booster servicing, will also be performed.

While Blackwell-Thompson did not share specific timings of these events (perhaps because, as officials keep saying, the timeline needs to be flexible due to the developmental nature of the mission), she noted that the astronauts will participate directly in a second "countdown demonstration test", following the first they did in December atop the rocket while inside the VAB. The second countdown, she added, will include "a walk-down of the emergency egress system."

Wet dress rehearsal

What everyone will be watching for, however, is the "wet dress rehearsal"—or testing of fueling and procedures during a simulated countdown—that NASA hopes to finish no later than Feb. 2, or four days before the Artemis 2 launch window opens on Feb. 6.

"During wet dress, teams demonstrate the ability to load more than 700,000 gallons of cryogenic propellants into the rocket, conduct a launch countdown, and practice safely removing propellant from the rocket without astronauts onsite," NASA officials wrote of the procedure Jan. 9.

It's a consequential moment not only for NASA and its mission partners, but also for the space community at large, because the Artemis 1 mission required at least four wet dress rehearsal attempts before NASA deemed the rocket safe to launch.

Blackwell-Thompson (who also helmed launch operations for Artemis 1) said NASA has learned a few things since then.

"It was a brand new vehicle," she acknowledged, saying part of the process was learning how to safely load liquid oxygen using the "legacy hardware" that has fueled other missions at KSC for decades. After the first two wet dress rehearsals, the team learned how to better regulate the fueling temperatures, she said.

Then hydrogen leaks arose during the third rehearsal, which led to NASA not only changing the way in which liquid hydrogen is loaded, but also modifying the ground umbilical plates that send power, coolant, fuel and communications to the rocket, according to Blackwell-Thompson.

The team "made some changes to that interface between the flight plate and the ground plate" to avoid the hydrogen leaks "where you have the flex hoses and the connections on the back of the plate." When leaks arose in a "cavity"—where ground plates come together—this was addressed through modifying "the flow rates, the temperatures, the pressures," she said.

A "replenish valve" in the ground equipment, which also proved tricky to manage during wet dress rehearsals, led to a design modification for Artemis 2. Cryogenic or super-cool fuels have already been tested with that valve "with as many cycles as we would expect to have during Artemis 2," Blackwell-Thompson said.

Blackwell-Thompson emphasized the team is prepared to take their time, and will only launch when they are safely ready. While Feb. 6 is the prime launch date for Artemis 2, windows are available in February, March and April at the least.

"We need to get through wet dress. We need to see what lessons that we learn as a result of that. And that will ultimately lay out our path toward launch," Blackwell-Thompson said. "With a wet dress that is without significant issues, if everything goes to plan, then certainly there are [launch] opportunities within February that could be achievable."