Nasa called off a test flight on Monday of its largest-ever rocket in a setback to the ambitious programme to send humans back to the Moon and eventually to Mars.
“We don’t launch until it’s right,” Nasa administrator Bill Nelson said after an engine temperature issue forced liftoff from Kennedy Space Centre to be scrubbed.
“This is a very complicated machine,” Nelson said.
Blastoff had been planned for 8:33am (1233 GMT) but was cancelled because of a temperature problem with one of the four engines.
Nasa said a test to get one of the engines to the proper temperature range for liftoff was not successful.
Nelson said delays were “just part of the space business” and expressed confidence that Nasa engineers will “get it fixed and then we’ll fly”.
Tens of thousands of people, including US Vice President Kamala Harris, had gathered near the Kennedy Space Centre in Florida to watch the launch.
The goal of the flight is to test the SLS and Orion crew capsule.
Mannequins equipped with sensors are standing in for a crew for the mission.
Overnight operations to fill the orange-and-white rocket with more than three million litres of ultra-cold liquid hydrogen and oxygen were briefly delayed by a high risk of lightning.
Around 3:00am, another hiccup emerged: a potential leak was detected during the filling of the main stage with hydrogen, causing a pause. After tests, the flow resumed.
Nasa engineers later detected the engine temperature problem and put a hold on the countdown before eventually scrubbing the launch.
The rocket’s Orion capsule is to orbit the Moon to see if the vessel is safe for people in the near future. At some point, Artemis aims to put a woman and a person of color on the Moon for the first time.
During the 42-day trip, the Orion capsule will orbit the Moon, coming within 60 miles (100km) at its closest approach, and then fire its engines to shoot out 40,000 miles — a record for a spacecraft rated to carry humans.
One of the mission’s primary objectives is to test the capsule’s heat shield, which at 16 feet in diameter is the largest ever built.
The craft will also deploy small satellites to study the lunar surface. A complete failure would be devastating for a programme costing $4.1 billion per launch that is already years behind schedule.
Life on the Moon
The next mission, Artemis 2, will take astronauts into orbit around the Moon without landing on its surface. The crew of Artemis 3 is to land on the Moon in 2025 at the earliest.
And since humans have already visited the Moon, Artemis has its sights set on another lofty goal: a crewed mission to Mars.
The Artemis programme is to establish a lasting human presence on the Moon with an orbiting space station known as Gateway and a base on the surface.