By delaying the launch due to engine problems - NASA is playing it safe, ITV News correspondent Robert Moore reports.
The space agency has assured the countdown will begin again next week, as it prepares for a launch set to mark the next chapter in putting humans back on the moon.
The Space Launch System rocket was set to lift off un-crewed on Monday, with three test dummies aboard its first flight.However the launch was called off by the launch director moments before it was due to get underway, after engineers found an 'engine bleed'.NASA said the first opportunity for the next Artemis 1 launch attempt will be Friday, 2 September, just before 1pm BST (8am EST), depending on how the engine issue develops.
The moon rocket's flight is the first in the space agency’s Artemis programme and will launch without a human crew for this mission.
However, there will be astronauts on board for subsequent missions, with the first crewed flight into space scheduled for 2024.
The Artemis 1 mission will see the first launch of the new 322ft tall Space Launch System (SLS) rocket, which the agency says is the world’s most powerful rocket to date.
It will take the Orion capsule, powered by the Airbus-built European Service Module (ESM), into the Moon’s orbit.
NASA's new moon mission could put humans on the moon as early as 2025 for the first time in over half a century, ITV News' Martha Fairlie reports.
The mission's duration is 42 days, 3 hours, 20 minutes, and in total it will travel 1.3 million miles, before splashing down in October.
If bad weather or other delays hamper the launch, the next window will be on 5 September, NASA said.
Cameras inside and outside Orion will then beam pictures and footage of the mission back to earth as the rocket begins its journey to the moon.
Stars including Jack Black, Chris Evans, Keke Palmer and Josh Groban were originally billed to appear at the live-streamed launch.
Following the postponement on Monday, NASA has said it will provide updates on the order of proceedings as it prepares for the second launch attempt.
Watch the Artemis 1 launch on Monday, 29 August live on NASA TV's official livestream here:
Why did NASA call off the Artemis 1 launch?
Experts at Nasa have explained in more detail the reasons for postponing the Artemis 1 rocket launch.
Michael Sarafin, Artemis mission manager, said the team encountered problems over the weekend and on Monday including lightning strikes, a fuel leak and the engine overheating, which forced them to postpone take-off.
Nasa administrator Bill Nelson has said rocket launch delays are “just part of the space business” in response to the postponement of the Artemis 1 test flight mission on Monday.
Speaking on Nasa’s official channel from the Kennedy Space Centre in Cape Canaveral, Florida, Mr Nelson said: “We don’t launch until it’s right, and in fact they’ve got a problem with the gases going on the engine bleed on one engine.
“I think it’s just illustrative that this is a very complicated machine, a very complicated system, and all those things have to work, and you don’t want to light the candle until it’s ready to go.
“I have some personal experience in the crew that I participated in the 24th flight of the space shuttle, we scrubbed four times, and the fifth try was a flawless mission.
“We know had we launched on any one of those scrubs, it wouldn’t have been a good day.
“This is just part of the space business and it’s part of particularly a test flight, we are stressing and testing this rocket and a space craft in a way that you would never do it with a human crew on board, that’s the purpose of a test flight.”
Earlier, the space agency said: “Launch director Charlie Blackwell-Thompson has called a scrub of the attempt of the launch of Artemis 1.
“The issue that came up was an engine bleed which couldn’t be remedied but the rocket is currently in a stable configuration.
“It was mostly tanked but not completely tanked.
“Engineers are now working on a plan to continue gathering data about this particular engine and the bleed that didn’t work out.”"Teams will continue to gather data, and we will keep you posted on the timing of the next launch attempt," NASA tweeted.
"We're going back to the Moon to stay" - ITV News correspondent Robert Moore previews NASA's newest launch to the Moon, before the postponement
When will humans next land on the Moon?
NASA expects the first Artemis astronauts to land on the Moon in 2025.
Airbus engineer Sian Cleaver is industrial manager for the ESM, and as a child dreamt about being involved in human spaceflight before getting a master’s degree in physics and astronomy from Durham University.
She said: “I’m ridiculously excited, and I think everybody on the team is.
“There’s years and years of a labour of love into this project.
“This is the first time that we will have seen one of our European service modules flying in space and going to the Moon.
“I think a lot of us couldn’t quite believe it – we’ve now got the go for launch on the 29th.
“Now, I think it’s really sinking in that this is reality, this is happening, and it’s going to really start this whole new chapter of space exploration, and going to the Moon.
“We’re on the brink of something really exciting now.”
Ms Cleaver explained that last time humans went to the Moon – some 50 years ago – it was about proving that it could be done whereas the new mission is about proving people can go there for longer and more sustainably.
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It will also assess whether some infrastructure can be built on and around the Moon, allowing humans to survive on another planetary body.
Now in her 30s, Ms Cleaver first visited the Kennedy Space Centre in Florida when she was just eight years old.
Her role in building the ESM involved making sure that all of the equipment and the subsystems came together at exactly the right time.
Speaking of attending the launch, she said: “I am so excited to be there.
“It is going to be, for me personally, a really special moment to be back there after so long. And now to actually work in the space industry, I still haven’t quite got my head around it really, that I’ve achieved something that I wanted to do since I was 15 or so.”
She added: “It’s pretty amazing that even at this stage of my career – 10 years into Airbus – that I’m working on essentially my dream mission.”
The UK is part of the Artemis programme, making contributions to the Lunar Gateway – a space station currently in development with the European Space Agency – working alongside the US, Europe, Canada and Japan.
The Artemis mission will be tracked in the UK from Goonhilly Earth Station in Cornwall.
Libby Jackson, exploration science manager at the UK Space Agency, said: “The first launch of the Artemis 1 SLS rocket is an important step for the global space community as we prepare to return humans to the Moon.
“The Artemis programme marks the next chapter of human space exploration and we look forward to continued involvement as it comes to life.”