CAPE CANAVERAL, Florida (AP) — NASA’s dress rehearsal for its mega moon rocket is off until at least this weekend because of a pair of technical problems that kept stalling a fuelling test.

Launch managers tried twice — once Sunday and again Monday — to load nearly one million gallons of fuel into the 322-foot (98-metre) rocket known as Space Launch System, or SLS. Balky fans at the launch pad thwarted the first effort, while a stuck valve halted the second attempt.

The countdown test is the last major milestone before the rocket’s long-awaited launch debut. The Orion crew capsule atop the rocket will be hurled to the moon in a passenger-less test flight, looping around but not landing before returning to Earth. NASA is targeting June, depending on how the demo goes.

“We didn’t get through everything we wanted, but certainly learned a great deal that we’ll take into our next attempt,” said NASA’s Jim Free, who’s in charge of exploration systems development.

Speaking Tuesday at the Space Foundation’s annual conference in Colorado Springs, Free said the launch team will wait until SpaceX launches four private passengers to the International Space Station before taking another crack at the fuelling test. Lift-off is scheduled for Friday from Kennedy Space Center, barely a mile from the pad holding the SLS rocket.

The dress rehearsal began Friday and should have lasted just two days. A severe thunderstorm resulted in four lightning strikes at the pad Saturday, but officials did not believe that caused any of the technical problems.

After this first moonshot in NASA’s Artemis programme, NASA will send a crew around the moon in 2024 and then attempt the first lunar landing by astronauts in 2025 or so. Astronauts last walked on the moon in 1972 during NASA’s Apollo programme.