NASA is moving a rocket set to send four astronauts into a flyby of the moon off the launchpad.

Postponed by NASA several times since it was rolled into launch position in late January 2026, new issues have left the Space Launch System (SLS) rocket unable to take off again.

The original launch window opened on February 6, 2026. The launch was first moved by a few days and then a month, into March. Now, Artemis II will not launch before April. 

Hydrogen and helium issues

Problems began almost immediately in February, with freezing cold weather delaying an essential "wet" rehearsal of the rocket fueling procedure, where 700,000 gallons (2.6 million liters) of liquid hydrogen and oxygen fuel are pumped into the SLS's tanks. 

When eventually conducted, the test was stopped when hydrogen leaks occurred — a problem that also grounded the Artemis I mission in 2022.

Repairs to the fuel connections saw NASA attempt the test again on February 20, setting a new launch date for March 6 at the earliest.

But while the hydrogen leaks were resolved in the retest, a problem with the flow of helium used to pressurize the liquid hydrogen and oxygen fuel tanks of the rocket's upper stage was later revealed. The helium flow issues cannot be resolved on the launchpad. So, the rocket had to be rolled back to its hangar.

Artemis II will now launch in April at the earliest

The Artemis program has been repeatedly delayed. 

After an uncrewed Artemis I mission in 2022 saw the Orion spacecraft's heat shield erode on Earth re-entry, NASA needed to undertake an extensive investigation to ensure a safe journey for the astronauts assigned to the crewed Artemis II flight.

Originally set to go up in 2023, administrative reviews saw the Artemis II launch pushed back to September 2025, and now 2026.

The mission's astronauts, Christina Koch, Victor Glover, Jeremy Hansen, and Reid Wiseman, will need to wait again to board Orion while NASA resolves its leak problems.

Moon launch windows have strict conditions

There are few opportunities — often calculated to the minute — to launch a safe and successful Moon mission.

Moon launch windows must meet stringent criteria so that the spacecraft can be "inserted" into its space flight path, complete its journey, and return to Earth. For Artemis II, launch windows are designed to:

• Release Orion into high Earth orbit from the SLS rocket, allowing careful monitoring of the astronaut life support systems on board.
• Ensure Orion is correctly aligned to the moon for a successful fuel burn to commence its journey.
• Not be in darkness for longer than 90 minutes to ensure adequate sunlight hits the European Service Module's solar array, which powers Orion's systems.
• Ensure Orion can be on course to return to Earth safely.

NASA's April window includes launch opportunities on April 1, 3, 4, 5, and 6.

Edited by: Zulfikar Abbany