NASA says the next attempt at a debut space flight of its "mega moon rocket" could happen as early as Friday, but engineers and other experts must first review a raft of problems that saw the Artemis mission's planned launch to be scrapped prior to liftoff.

NASA endured several issues at the Kennedy Space Center in Florida Monday morning. First, it was the unco-operative weather, with thunderstorms delaying the propellant load for the rocket. 

Once the go-ahead was given to fill the fuel tanks — which altogether hold 2,778,492 litres of propellant, or the equivalent of 41 swimming pools of water — another issue arose: the liquid oxygen and liquid hydrogen were filling at unacceptable rates relative to one another. The process was repeatedly stopped and started due to a hydrogen leak, before teams were able to reduce the seepage.

The tanks were being filled with super-cooled liquid oxygen and hydrogen propellants, and launch teams began a "conditioning" process to chill the engines sufficiently for liftoff, NASA said.

But one of the four main engines failed to cool down as expected, and while trying to resolve that issue, the team noticed another leak, involving a vent valve higher up on the rocket, prompting launch team managers to pause the countdown and then call off the launch at 8:35 a.m. ET.

Engineers struggled to pinpoint the source of the cooling problem well after the launch postponement was announced. 

Launch director Charlie Blackwell-Thompson and her team also had to deal with sluggish communication between the Orion capsule and launch control. The problem required what turned out to be a simple fix.

Even if there had been no technical snags, thunderstorms ultimately would have prevented a liftoff, NASA said. Dark clouds and rain gathered over the launch site as soon as the countdown was halted, and thunder echoed across the coast.

The launch team will reconvene on Tuesday afternoon to review data on the problems, and develop options for the next launch attempt, Sarafin said.

"[There were] a number of challenges. We were ready for some of them, and the technical challenges we encountered on the engine bleed and the vent valve are just some things we're going to have to look at tomorrow after we get a little smarter and get rested."

Asked by reporters whether a Friday launch was possible, he said that day was "definitely in play," although it was possible the launch could be delayed until mid-September or later.

The problems seen Monday were reminiscent of NASA's space shuttle era, when hydrogen fuel leaks disrupted countdowns and delayed a string of launches back in 1990.

"This is a very complicated machine, a very complicated system, and all those things have to work, and you don't want to light the candle until it's ready to go," said NASA administrator Bill Nelson.

The start of the Artemis mission, Artemis I, won't involve any crew on board — except for three mannequins and a plush Snoopy — but it is a crucial step in returning humans to space. 

Artemis II is set to launch in 2024 or 2025, with four astronauts who will orbit the moon, including a Canadian.

The last time anyone was on the moon was in December 1972.

In the first 10 minutes after liftoff, a lot happens. The solid rocket boosters separate, the launch abort system jettisons and the core stage — the big orange tank — separates and falls back to Earth. At 8:51 ET Orion's solar arrays, used to power the spacecraft, deploy, which will take roughly 12 minutes.

Then Orion needs to get into position to head on course to the moon. To do this, there are several manoeuvres, which continue throughout the day, which NASA will be watching very closely. 

If all goes well, Orion will be on an outbound trip to the moon that will continue five days after launch. When it gets there, it has to move into a very particular orbit which will take a further three days.

Finally, 35 days after Orion left Earth, the spacecraft will begin its trip home, where it is scheduled to splash down in the Pacific Ocean off the coast of San Diego on October 10.

After Orion returns home, NASA will evaluate all the systems and tests they conducted along the way, preparing for Artemis II. 

Canadian Space Agency astronauts Jeremy Hansen and Joshua Kutryk — one of four Canadian astronauts who may be on that Artemis II mission — were at the Kennedy Space Center ahead of the launch and said that the Artemis I mission is just the first step. 

"In the end we will go back to the moon, but it is completely different this time. Not only are we going to a different location, there's going to be new science, new technology, but we also have our eyes on Mars," Hansen said.

"This is a proving ground to take humanity into deep space. This is just the first steps of something much, much grander."

Kutryk was keen to point out that this isn't just a U.S. effort.

"This isn't just NASA … this is a world effort. This is NASA leading the world along to go out and accomplish these really hard challenges to try to set up — not just a U.S. — but a human presence on the moon and then eventually on Mars," Kutryk said.

"So it's very different in that respect and it's very important in that respect that we're bringing the world along."

Based in Toronto, Nicole covers all things science for CBC News. As an amateur astronomer, Nicole can be found looking up at the night sky appreciating the marvels of our universe. She is the editor of the Journal of the Royal Astronomical Society of Canada and the author of several books. In 2021, she won the Kavli Science Journalism Award from the American Association for the Advancement of Science for a Quirks and Quarks audio special on the history and future of Black people in science. You can send her story ideas at Nicole.Mortillaro@cbc.ca.

With files from Reuters and The Associated Press

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