NASA has aborted a second launch attempt for its giant Moon rocket because of yet another fuel leak.
Mission managers called off preflight operations on Saturday, about three hours before the 2:17pm EDT (18:17 GMT) liftoff time targeted for the Space Launch System (SLS) rocket and its Orion capsule from Cape Canaveral, Florida.
The previous attempt on Monday was also marred by escaping hydrogen, but those leaks were elsewhere on the 98-metre (322-foot) rocket, the most powerful ever built by NASA.
The latest setback could delay the inaugural flight of NASA’s Moon-to-Mars Artemis programme for weeks, if not months.
The uncrewed test flight, aimed at launching the capsule to the Moon and back, was to have marked the inaugural voyage of both the SLS and Orion a half-century after the last Apollo lunar mission, the forerunner of the Artemis program.
The countdown was scrubbed after Kennedy Space Center technicians made three failed attempts to fix a “large” leak of supercooled liquid hydrogen propellant being pumped into the rocket’s core-stage fuel tanks.
Officials said the leak was too tricky and time-consuming to finish troubleshooting and fix on the launch pad before the current launch period allotted to the mission expires on Tuesday.
This means the earliest opportunity to try again would come during the next launch period that runs September 19 to 30, or during a subsequent October window, an associate NASA administrator, Jim Free, told reporters at a late-afternoon briefing.
The spacecraft will now be rolled back into its assembly building.
NASA Administrator Bill Nelson stressed that safety is the top priority, especially on a test flight like this where everyone wants to verify the rocket’s systems “before we put four humans up on the top of it”.
Those odds did not stop spectators from jamming the Florida coast to see the SLS rocket soar. Local authorities had expected enormous crowds because of the long Labor Day holiday weekend.
Al Jazeera’s Alan Fisher, reporting from Cape Canaveral, said thousands of people had gathered in anticipation of the planned launch.
“It’s a real disappointment for the thousands of people who came to this part of Florida to watch a lunar launch on the space coast … A lot of people made a special effort to come here just to see the launch,” he said.
“Nobody wants to be planning a space launch and hear those clichéd and fatal words – ‘We have a problem,’ – but that is clearly what happened here.”
The $4.1bn test flight is the first step in NASA’s Artemis programme for renewed lunar exploration, named after Apollo’s twin sister in Greek mythology.