Nasa’s highly anticipated Artemis 1 Moon mission launch was postponed on Monday owing to problems engineers faced with one of the engines of the rocket.
The 101-metre Space Launch System was scheduled for a lift-off on Monday, 4.33pm GST, with a two-hour launch window, from Florida’s Kennedy Space Centre.
The next launch attempt will be made on September 3, 10.17pm, GST.
Artemis 1 is an uncrewed test flight that will launch the Orion spacecraft around the Moon to allow engineers to measure its performance.
On Monday, the rocket’s core stage was successfully fuelled with 3.31 million litres of fuel, including liquid oxygen and liquid hydrogen.
However, engineers had a problem with one of the four RS-25 core stage engines when it would not ‘bleed’ properly — a process where liquid hydrogen fuel is sent to the engines to help them condition for ignition.
This made it difficult for the engine to reach a temperature that was required for a launch.
"We held at T-40 minutes and counting, after the teams were unable to get past an engine bleed that didn't show the right temperature and ultimately the launch director has called a scrub for the day," Nasa said in the live stream.
The liquid hydrogen engine chill was a process Nasa wanted to test during a wet dress rehearsal in spring, but were unable to. This was the first time the team was able to see it live.
They also ran into other problems earlier on during fuelling, including a hydrogen leak in the core stage tank that reappeared in the same place during a dress rehearsal.
Nasa said the leak was in “acceptable levels” and pressed ahead with the fuelling.
The team also found what appeared to be a crack in the rocket’s intertank, an area that connects the liquid hydrogen and liquid oxygen tanks.
Ice had formed on the intertank, on the exterior of the core stage.
The problem was later resolved after it was confirmed that it was not actually a crack in the core stage tank, but on the foam, which made it appear as if it was causing a leak.
The issues caused delays in the countdown, as well as the start of the official launch broadcast on Nasa’s YouTube channel, which had more than 115,000 people waiting.
US Vice President Kamala Harris and Second Gentleman Doug Emhoff had arrived at the space centre to witness the launch.
There were also celebrity appearances planned, such as by actors Jack Black, Chris Evans and Keke Palmer, as well as performances of The Star-Spangled Banner by Josh Groban and Herbie Hancock and America the Beautiful by The Philadelphia Orchestra and cellist Yo-Yo Ma.
If the Artemis 1 mission is successful, it will pave the way for crewed missions under the Artemis programme, which aims to return astronauts to the lunar surface.
Artemis 2, a crewed flight around the Moon, could take place as early as 2024 if this test flight goes as planned.
Artemis 3, the first human lunar landing mission under the programme, has been delayed until 2025.
Nasa was directed by the US Congress to develop the rocket in the hope that it would return American astronauts to the Moon again, after nearly 50 years since the Apollo programme ended.
The space agency has built the Space Launch System with technology used in the Space Shuttle programme, for example the solid rocket boosters and RS-25 core engines.
The rocket will lift off with 3,991 tonnes of thrust, soaring at speeds of 40,233 kilometres an hour in about eight minutes to reach space.
It will deliver the Orion spacecraft — the same capsule astronauts will ride in once crewed missions begin — to space.
From there, the spacecraft will travel 450,616km from Earth, thousands of kilometres beyond the Moon, over the course of about four to six weeks.
It will fly about 100km above the lunar surface, and then use the Moon’s gravitational force to propel itself into an opposite orbit about 70,000km from the Moon.
Orion will stay in that orbit for about six days to collect data and allow mission control to assess its performance.
Then, it will make its journey back to Earth and will splash down off the coast of the Mexican state of Baja California.