NASA delays crucial Artemis 1 moon mission test to April 12

NASA has pushed back the resumption of the Artemis 1 moon mission's critical "wet dress rehearsal" by two days, to Tuesday (April 12).

The agency had planned to restart the wet dress — a practice run of rocket fueling and other important Artemis 1 prelaunch activities — today (April 9) at Pad 39B of the Kennedy Space Center (KSC) in Florida. 

But the mission team decided to modify the test procedure after noticing a problem with a "helium check valve," which prevents the gas from escaping out of Artemis 1's huge Space Launch System (SLS) rocket. Helium is used to clear engine lines before loading and draining propellant, NASA officials explained in an Artemis 1 update today.

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The modified wet dress rehearsal will focus primarily "on tanking the [SLS] core stage, and minimal propellant operations on the interim cryogenic propulsion stage (ICPS) with the ground systems at Kennedy," agency officials wrote in the update. (The ICPS is the upper stage of the two-stage SLS.) 

"Due to the changes in loading procedures required for the modified test, wet dress rehearsal testing is slated to resume with call to stations on Tuesday, April 12 and tanking on Thursday, April 14," they added.

This isn't the first delay for the Artemis 1 wet dress rehearsal. The test got underway on April 1, and the mission team had hoped to wrap things up about 48 hours later, on April 3. But several issues emerged, including a glitch with the fan system on the SLS's huge mobile launch tower and a stuck pressure-relieving vent valve on the structure.

These problems initially delayed and then halted the test, as the Artemis 1 team stood down to accommodate the launch of Axiom Space's Ax-1 mission to the International Space Station. Ax-1 lifted off yesterday (April 8) from KSC's Pad 39A, which is next door to 39B, and its departure cleared the way for Artemis 1's wet dress to continue.

Artemis 1 will launch an uncrewed Orion spacecraft on a roughly month-long mission around the moon. NASA won't set a target launch date until the wet dress rehearsal is complete and teams have analyzed the resulting data, but the mission is unlikely to lift off before June.

If all goes well with Artemis 1, Artemis 2 will launch astronauts around the moon in 2024 and Artemis 3 will land a crew near the lunar south pole in 2025 or 2026.

Mike Wall is the author of "Out There" (Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for alien life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or on Facebook.