SpaceX is counting down the days to Monday’s first test flight of Starship, the most powerful rocket ever designed to take astronauts to the moon, Mars and beyond.

The giant rocket is scheduled to blast off at 8 am CST (1300 GMT) from SpaceX’s Starbase spaceport in Boca Chica, Texas.

If Monday’s launch attempt is delayed, a fallback would be scheduled for later this week, billionaire SpaceX founder Elon Musk said was a distinct possibility.

“It is a very risky flight,” Musk said during a live event on Twitter Spaces on Sunday. “This is the first launch of a very complex and massive rocket.

“There are a million ways this rocket could fail,” he added. “We’ll be very careful, and if we find anything that concerns us, we’ll postpone.”

Musk said he wanted to “reduce expectations” because “if it makes it to orbit, it might not make it tomorrow.”

The US space agency NASA has selected the Starship spacecraft to carry astronauts to the moon in late 2025, the first mission known as Artemis III since the end of the Apollo mission in 1972.

Starship is a 164-foot (50-meter) spacecraft atop a 230-foot-tall first-stage Super Heavy booster rocket designed to carry crew and cargo.

The spaceship and super-heavy rocket, collectively known as Starship, have never flown together. However, there have been several suborbital test flights of spacecraft alone.

If all goes according to plan, the Super Heavy booster will separate from Starship about three minutes after launch and splash down in the Gulf of Mexico.

With six of its own engines, Starship will continue to fly nearly 150 miles up, nearly once around the Earth, before crashing into the Pacific Ocean about 90 minutes after launch.

“If it makes it to orbit, it will be a huge success,” Musk said.

“If we were far enough from the launch pad before something went wrong, then I think I would consider it a success,” he said. “Just don’t blow up the launch pad.

“The payload of this mission is information,” he said. “Information that will enable us to improve the design of future Starship builds.”