Nasa will re-test its mega Moon rocket, after failing to complete a first attempt last month.
The Space Launch System (SLS) was taken back to the garage for repairs in April, so engineers could fix a faulty helium check valve and the source of a hydrogen leak.
The space agency had rolled out the rocket and the Orion spacecraft to a launch pad in Florida for fuelling and a practice launch countdown, in a process known as a wet dress rehearsal.
However, after three failed attempts, the world's most powerful rocket was taken back to the Vehicle Assembly Building for repairs.
While the rocket did make some progress during the test, complete fuelling and pressurisation did not take place, neither did the countdown sequence that allows engineers to measure important details.
The SLS will be brought again to the launch pad at Kennedy Space Centre on June 6, with another test attempt planned for June 19.
“Engineers successfully completed work on items identified during the previous wet dress rehearsal tests, including replacing and testing an upper stage check valve and fixing a small leak within the tail service mast umbilical ground plate housing,” said Nasa on its website.
“Teams also completed some tasks originally scheduled to take place in the Vehicle Assembly Building after wet dress rehearsal.”
After the test, Nasa hopes to launch the rocket as part of the Artemis 1 mission.
The mission will be the first under the Artemis programme, which seeks to build a sustainable human presence on the Moon and land the next man, first woman and first person of colour on the lunar surface.
The test flight was expected to take place in the summer, but because the wet dress rehearsal has not been completed yet, it will likely take place later this year.
“The rehearsal is the final test needed before launch, and calls for Nasa to test the system, including operations to load propellant into the rocket’s tanks, conduct a full launch countdown and demonstrate the ability to recycle the countdown clock,” said Nasa.
The tanks will also be drained to give scientists an opportunity to practise the timelines and procedures they will use for launch, the US space agency said.
During launch, the SLS will take off with 3,991 tonnes of thrust, soaring at speeds of 40,233 kilometres per hour in about eight minutes to reach space. It will deliver Orion into its intended orbit, where it will begin its journey towards the Moon.
The spacecraft will fly 100 kilometres above the Moon’s surface and then use its gravitation force to be captured into an opposite orbit about 70,000km from the Moon.
It will stay there for about six days to collect data and to allow mission control to measure the spacecraft’s performance.
The launch of Artemis 2 is planned for 2024 and includes a crewed mission that will orbit the Moon.
Artemis 3, the first human lunar mission under the programme, has been delayed until 2025.