What to know about Artemis II's 'wet dress rehearsal'

Preparations are underway to begin critical testing of NASA spacecraft for the Artemis II mission that will send four astronauts around the moon.

Fuel testing is set to begin Monday, NASA says. The fueling phase of prelaunch testing known as a "wet dress rehearsal" was delayed because of freezing temperatures at the launch pad located at NASA's Kennedy Space Center in Florida.

Here is what to know about preparations and the mission.

What exactly is a wet dress rehearsal?

A wet dress rehearsal is a designated time before launch when engineers and crew conduct testing of the spacecraft. During this final test, the Orion spacecraft that will house the astronauts and the Space Launch System (SLS) rocket will be checked over the course of a detailed countdown schedule.

A countdown clock began at 8:13 p.m. ET on Saturday, counting down to the simulated liftoff on Monday evening.

On Monday, more than 700,000 gallons of fuel containing liquid oxygen and liquid hydrogen is scheduled to be loaded into the rocket. Launch teams will also practice removing the fuel from the rocket and will conduct a launch countdown.

A simulated launch window will start at 9 p.m. ET and is expected to last until 1 a.m.

The Orion spacecraft has been powered up for several days because of the cold weather and engineers are preparing to charge its flight batteries, NASA said on Sunday.

The chance for the Artemis II mission launch, which was scheduled to occur as early as this coming Friday, will now take place no earlier than next Sunday, according to NASA. There are also launch opportunities in March and April.

The mission is set to last for 10 days and will send astronauts around the Earth and then around the moon before heading back to Earth. It's the first crewed mission to fly to the moon in more than 50 years. The Artemis II mission is a step toward the goal of returning humans to the moon's surface and then eventually to Mars.

Artemis II astronauts are not part of prelaunch testing

NASA astronauts Victor Glover, Christina Koch and Reid Wiseman along with Canadian Space Agency astronaut Jeremy Hansen will not be on the spacecraft during testing.

The Artemis II mission astronauts have been in quarantine in Houston since Jan. 23. This is to limit their exposure to others and ensure they do not become ill prior to launch. During quarantine, the astronauts wear masks, avoid public spaces and keep contact with family, friends and colleagues as long as they follow quarantine guidelines, according to NASA.

If prelaunch testing goes well, the astronauts will fly to Kennedy Space Center in Florida six days before launch where they will live in astronaut crew quarters inside the Neil Armstrong Operations and Checkout Building.
Copyright 2026 NPR