NASA on Monday was forced to cancel the blast-off of its next-generation moon rocket's no-crew debut test flight because of fuel leaks and a temperature issue with one of the four RS-25 engines.
The next launch attempt will not take place until Friday at the earliest.
The 98-meter (322-foot) Space Launch System rocket was set to lift off Monday morning with three test dummies aboard on its first flight, a mission to propel a capsule into orbit around the moon.
As precious minutes ticked away, NASA repeatedly stopped and started the fueling of the Space Launch System rocket with nearly 1 million gallons of super-cold hydrogen and oxygen because of a leak. The fueling already was running nearly an hour late because of thunderstorms off Florida's Kennedy Space Center.
The leak of highly explosive hydrogen appeared in the same place that saw seepage during a dress rehearsal back in the spring.
Then a second apparent hydrogen leak turned up in a valve that had caused trouble in June but that NASA thought it had fixed, officials said.
Later in the morning, NASA officials spotted what they feared was a crack or some other defect on the core stage – the big orange fuel tank with four main engines on it – but they later said it appeared to be just a buildup of frost.
The rocket was set to lift off on a mission to put a crew capsule into orbit around the moon. The launch represents a milestone in NASA's quest to put astronauts back on the lunar surface for the first time since the Apollo program ended 50 years ago.
After the scrubbed Monday launch, the next attempt will not be until Friday at the earliest.
The 98-meter (322-foot) spaceship is the most powerful rocket ever built by NASA, out-muscling even the Saturn V that took the Apollo astronauts to the moon.
No astronauts were inside the rocket's Orion capsule. Instead, the test dummies, fitted with sensors to measure vibration, cosmic radiation and other conditions, were strapped in for the six-week mission, scheduled to end with the capsule's splashdown in the Pacific in October.
Even though no one was on board, thousands of people jammed the coast to see the rocket soar. Vice President Kamala Harris was expected among the VIPs.
The launch is the first flight in NASA's 21st-century moon-exploration program, named Artemis after Apollo’s mythological twin sister.
Assuming the test goes well, astronauts will climb aboard for the second flight and fly around the moon and back as soon as 2024. A two-person lunar landing could follow by the end of 2025.