NASA on Monday set Sept. 2 as its goal to launch a new moon mission rocket after calling off its launch just hours prior due to problems with fueling its brand-new engine.

"Scrubs are just a part of this program," said NASA Administrator Bill Nelson. "This is a brand-new rocket. It's not going to fly until it's ready."

NASA officials said they encountered an issue with chilling down one of the rocket's four engines during the bleed process of the engine, from which compressed air is removed right before launch. The team also found a problem with one of the rocket's vent valves.

"The combination of not being able to get the Engine 3 chilled down and then the vent valve issue that they saw at the inner tank really caused us to pause today," said Artemis Mission Manager Mike Sarafin.

"I think we all want to see that next milestone, that next step, and seeing smoke and fire is something that everybody enjoys, but we're not going to let another hurdle deter us from trying to achieve that next step."

Rain and lightning during the takeoff window also contributed to NASA's decision to scrub the launch, though erring on the side of caution remained the most important factor.

"We continue to learn. That's what we're doing," said NASA Associate Administrator for Exploration Systems Development Jim Free.

"We're testing the people and the processes ... and then figure out a path forward, which is ultimately where we want to go."

The Artemis 1 mission is the first in a series of three NASA space flights to the moon.

This first mission is an unmanned flight with three test dummies aboard. It will evaluate the integration of NASA's deep space exploration systems, which involve the Orion spacecraft and Space Launch System (SLS) rocket.

NASA administrators said they were trying to make sure every aspect of the Artemis I launch performed perfectly because the Artemis II mission would be the first space flight to take live crew members aboard the new system.

"When you're dealing in a high-risk business -- and space flight is risky -- that's what you do. You buy down that risk, you make it as safe as possible ...That's the whole reason for this test flight: To stress it and to test it to make sure it's as safe as possible," said Nelson.

"There are millions of components of this rocket and its systems ... and needless to say, the complexity is daunting when you bring it all into the focus of a countdown."

NASA officials said they would analyze all of the information and data from Monday's Orion and SLS launch delay over the next 48 to 96 hours and try for another attempt on Sept. 2.

"We're going to launch when we're ready and that's our approach," said Free.

"We won't know until we know, but we also won't know until we try."