The US space agency says it will try to launch its new Moon rocket on Saturday.
A lift attempt on Monday had to be scuppered when one of the vehicle’s four engines would not cool to its required operating temperature.
After examining the data, engineers believe they now understand why the problem occurred.
They believe it is likely related to an inaccurate sensor reading and that they can develop a strategy to address the issue on launch day.
This includes starting the cooling process of the motors earlier in the countdown.
“We have a path forward to get where we need to go, to support the next launch,” said John Honeycutt, who manages the Space Launch System (SLS) rocket project at Nasa.
Saturday’s launch will take place at 14:17 local time (18:17 GMT, 19:17 BST) at the Kennedy Space Center in Florida.
Controllers will have two hours to get the rocket off the ground.
The SLS is the largest launch vehicle ever developed by the US space agency.
It’s the modern equivalent of the Saturn V rockets that sent men to the Moon in the 1960s and 70s – but with much more thrust from the launch pad.
SLS will send a new large crew capsule called Orion on a series of missions to the Moon as part of Nasa’s Artemis program. This first mission is called Artemis I and will be an uncrewed demonstration.
The reason for Monday’s rub was not related to the engine itself (Engine Number 3), but rather to the system that requires it to fly.
The power unit must not be shocked by the sudden injection of supercooled propellants. Instead, it must slowly cool down to the correct operating temperature (-250 C) prior to launch by venting through liquid hydrogen from the stage core tank above.
On Monday, sensor readings showed that the engine was 15-20 degrees Celsius less than where it should be.
Engineers believe the transit system was working properly. it was simply that the sensor system did not accurately reflect the actual temperature conditions.
The engineering team plans to start the cooling process about 45 minutes earlier in Saturday’s countdown, hoping that will bring everything into line.
“We’re going to try to launch on the third (of September). And, you know, taking into account that previous attempt, yesterday’s attempt, we said if we couldn’t thermally regulate the engines we wouldn’t launch, and that’s the same stance we’re going to take on Saturday,” said Mike Sarafin, director of Nasa’s Artemis mission.
The weather forecast for Saturday is not bright. Currently, there is a 60% chance that controllers will encounter a violation of launch criteria – mainly showers. The SLS is not allowed to take off in the rain.
But meteorologist Mark Berger struck a positive note.
“We’ve got two hours to work with. The showers tend to have quite a bit of real estate between them, so I still think we have a very good chance weather-wise to get going on Saturday,” he told reporters.
The purpose of the upcoming 42-day mission is to send Orion around the far side of the Moon before bringing it home for a crash in the Pacific Ocean off California.
A main goal of the test battle is to test that the heat shield in the capsule can survive the heat of re-entry into the Earth’s atmosphere.
Nasa says it will return to the Moon as part of a stepping stone to learn how to get to Mars. But researchers say there’s also unfinished business on the Moon, scientifically. We need to understand more about lunar origins and by extension the formation and early evolution of Earth.
Future Artemis missions will target the lunar South Pole where permanently shadowed craters hold ice reserves.
“Artemis is a series of increasingly complex missions to explore the Moon in preparation for missions to Mars. When we go to Mars, the more we can learn about what resources are available to us and how to use them , the better prepared” they will be,” NASA chief scientist Kate Calvin told BBC News.