NASA will make a second attempt to launch its giant moon rocket Artemis-1 on Saturday after Monday's take-off had to be cancelled.
The Artemis programme aims to put humans back on the moon by 2025 but got off to an inauspicious start when engineers detected a hydrogen leak in the rocket earlier this week.
The first flight in the agency’s programme is an un-crewed ship that was supposed to set off on a 42-day trip with Shaun the Sheep on board.
Monday's launch then ran into further problems as they were unable to communicate between the ground teams and Orion spacecraft.
A crack was detected but later said to have posed no safety issue but things got even worse after issues with engine three meant that the launch clock was paused a T-minus 40 minutes.
They were unable to get the engine down to the required temperature and even after diverting further coolant through it they couldn't get it to a safe temperature.
The delay was in place for almost an hour but ultimately this led to the flight being scrubbed and NASA made the announcement around 1:33pm - when the spaceship was originally due to take off.
The prospects for success on Saturday would appear to be clouded by weather reports predicting just a 40% chance of favourable conditions, while the US space agency acknowledged that some outstanding technical issues still need to be solved.
At a media briefing a day after Monday's first countdown ended with the flight scrubbed, NASA officials said Monday's experience was useful in trouble-shooting some problems and that additional difficulties could be worked through in the midst of a second launch try.
For now, NASA officials said, plans call for keeping the 32-story-tall Space Launch System (SLS) rocket and its Orion astronaut capsule on its launch pad to avoid having to roll the massive spacecraft back into its assembly building for a more extensive round of tests and repairs.
If all goes as hoped, the SLS will blast off from the Kennedy Space Centre in Cape Canaveral, Florida, on Saturday afternoon, during a two-hour launch window that opens at 2:17p.m., sending the Orion on an un-crewed, six-week test flight around the moon and back.
The long-awaited voyage would kick off NASA's moon-to-Mars Artemis program, the successor to the Apollo lunar project of the 1960s and '70s, before US human space-flight efforts shifted to low-Earth orbit with space shuttles and the International Space Station.
NASA's initial Artemis I launch attempt on Monday ended after data showed that one of the rocket's main-stage engines failed to reach the proper pre-launch temperature required for ignition, forcing a halt to the countdown and a postponement.
The first voyage of the SLS-Orion, a mission dubbed Artemis I, aims to put the vehicle through its paces in a rigorous demonstration flight pushing its design limits, before NASA deems it reliable enough to carry astronauts.
Named for the goddess who was Apollo's twin sister in ancient Greek mythology, Artemis seeks to return astronauts to the moon's surface as early as 2025, though many experts believe that time frame will likely slip by a few years.
The last people to walk on the moon were the two-man descent team of Apollo 17 in 1972, following in the footsteps of 10 other astronauts during five earlier missions beginning with Apollo 11 in 1969.
Artemis also is enlisting commercial and international help to eventually establish a long-term lunar base as a stepping stone to even more ambitious human voyages to Mars, a goal NASA officials say would probably take until at least the late 2030s to achieve.
