For the second time in five days, NASA on Saturday halted a countdown in progress and postponed a planned attempt to launch the 32-story-tall Space Launch System (SLS) rocket and its Orion capsule, the first mission of the agency's moon-to-Mars Artemis program.
The latest attempt to launch was scrubbed after repeated attempts by technicians to correct a leak of super-cooled liquid hydrogen propellant being pumped into the vehicle's core-stage fuel tanks.
"Multiple troubleshooting efforts to address the area of the leak by reseating a seal in the quick disconnect where liquid hydrogen is fed into the rocket did not fix the issue. Engineers are continuing to gather additional data," NASA said.
On Monday, hydrogen fuel escaped from elsewhere in the rocket, and the launch was postponed.
NASA could reschedule another launch attempt for next Monday or Tuesday, but there was no immediate information on when it might try again. A two-week lockdown period for launch begins after Tuesday. The extensive repairs could require the missile to be towed back to its hangar, potentially delaying flight until October.
Earlier on Saturday mission managers at Kennedy Space Center in Florida were positive that the launch would go ahead.
There will be no crew aboard the Artemis 1, with the mission testing whether the Orion capsule, which sits atop the SLS rocket, is safe to carry astronauts in the future.
Yet hundreds of thousands of people were expected to gather on nearby beaches to witness NASA's attempt to send its most powerful rocket into space.
Back to the moon
The long-awaited launch would kick off NASA's moon-to-Mars Artemis program — the agency's first major lunar expedition since the Apollo program of the 1960s and '70s.
It will take several days for the Orion spacecraft to reach the moon, with the entire trip expected to last six weeks.
At least six of those days will be spent in a distant orbit of the moon, flying around 60 miles (100 kilometers) from the celestial body at its closest approach.
The plan is that Orion would be returning to Earth for a splashdown in the Pacific Ocean in October.
One of the mission's main objectives is to test the Orion capsule's heat shield, which is the largest ever built at 16 feet (nearly 5 meters) in diameter.
On its return to Earth's atmosphere, the heat shield will have to withstand speeds of 25,000 miles per hour (about 40,000 kilometers per hour) and a temperature of roughly 5,000 degrees Fahrenheit (2,760 degrees Celsius), roughly half as hot as the sun.
Artemis is named after the twin sister of the Greek god Apollo, after whom the first moon missions were named.
