What we know about NASA's Artemis II lunar flyby mission

NASA’s historic Artemis II lunar flyby mission has hit a snag, pushing its launch timeline to no earlier than April. On Wednesday, NASA had to roll its massive Space Launch System rocket, weighing 11 million pounds, back to its hangar at Kennedy Space Center in Cape Canaveral, Fla., to repair an issue that would affect the proper flow of fuel into the rocket's engines.

Engineers discovered the issue with the 322-foot-tall rocket less than 24 hours after a successful wet dress rehearsal, which is an hourlong test that involves fully loading the rocket with more than 700,000 gallons of cryogenic propellant and running through a simulated launch countdown.

Here’s what to know about the Artemis program and mission:

What is the Artemis program’s mission?

The Artemis program is NASA’s long-term mission to return humans to the moon to establish a continuous human presence. The goal is to develop a lunar settlement on the south pole, a region where it’s believed water ice is abundant and could be used for drinking, breathing and as a source for rocket fuel.

Artemis’ long-term mission is to also lay the foundation for future crewed missions to Mars. The program is building on the legacy of the Apollo-era missions to the moon in the late 1960s and early ’70s. The Artemis program is aptly named after the ancient Greek goddess of the moon, twin sister of Apollo.

The program consists of a series of missions that started with Artemis I. The integrated flight test was successfully completed in November 2022, involving NASA’s deep space exploration systems. Those include the Orion spacecraft, the Space Launch System (SLS) rocket and upgraded systems at the Kennedy Space Center in Cape Canaveral, Fla.

What is the goal of the Artemis II mission?

“Artemis II builds on the success of the uncrewed Artemis I in 2022, and will demonstrate a broad range of capabilities needed on deep space missions,” NASA says on its website.

The Artemis II mission will be the first U.S. human lunar spaceflight in over 50 years. It will also be the first time that NASA’s SLS rocket and Orion capsule will be crewed.

The four astronauts on Artemis II won’t be landing on the moon, but instead, they’ll venture 600,000 miles around the moon and will return at 30 times the speed of sound, according to NASA. During their 10-day trip, they’ll test life support systems in the Orion capsule for future crewed missions to the moon’s surface. A moon landing would occur during Artemis III, which is targeted to launch by 2028.

Who are the Artemis II crew members?

NASA’s Reid Wiseman, Victor Glover and Christina Koch, and Canadian Space Agency astronaut Jeremy Hansen are the crew members for Artemis II. Koch is set to be the first woman to travel to lunar space, while Glover is the first person of color to do so.

Due to the delay in the launch of Artemis II, all four astronauts were able to come out of quarantine in preparation for the launch on Saturday and attended President Trump’s State of the Union speech on Tuesday.

When will Artemis II launch?

NASA Administrator Jared Isaacman said in a post on X that due to issues with the fueling system of the SLS rocket that will propel the astronauts into deep space, the March launch window is no longer possible.

NASA previously identified April 1, 3, 4, 5, 6 and 30 as potential launch days.