Nasa is preparing to roll out its most powerful rocket yet before a mission to send astronauts around the moon and back again for the first time in more than 50 years.

The Artemis II mission is scheduled to launch from Kennedy Space Center in Florida as early as 6 February, taking its crew on a 685,000-mile round trip that will end about 10 days later with a splashdown in the Pacific Ocean.

The flight will mark only the second test of Nasa’s Space Launch System (SLS) rocket and the first with a crew onboard. The four astronauts will live and work in the Orion capsule, testing life support and communications systems and practising docking manoeuvres.

Jared Isaacman, the billionaire private astronaut sworn in as Nasa’s administrator in December, said on Thursday the mission was “probably one of the most important human spaceflight missions in the last half-century”.

It will be the second time in space for three Nasa astronauts, Reid Wiseman, Victor Glover and Christina Koch, and the first for Jeremy Hansen, a Canadian astronaut. Koch will become the first woman, and Glover the first person of colour, to travel beyond low Earth orbit.

The astronauts will not land on the moon or enter lunar orbit, but will be the first to travel around the moon since Apollo 17 in 1972. The mission follows an uncrewed test flight in 2022 and paves the way for Artemis III, which aims to land astronauts near the lunar south pole as early as next year.

“These are the kinds of days that we live for,” John Honeycutt, the chair of the Artemis II mission management team, told a press briefing on Friday. “It really doesn’t get much better than this: we are making history.”

“It’s a big deal,” said David Parker, the former head of the UK Space Agency and a visiting professor at the University of Southampton. “It is a step towards what we in the space world always dreamed of: the sustained human and robotic exploration of the moon and, one day, on to Mars.”

Some paint the return to the moon as a second space race, with the US competing against China, which hopes to put its own boots on the moon by 2030. “I’ll be damned if the Chinese beat Nasa or beat America back to the moon,” Sean Duffy, Nasa’s former acting administrator, said in September. “We’re going to win.”

The SLS rocket and Orion capsule stand nearly 100 metres tall, with the rocket carrying more than enough liquid propellant to fill an Olympic-sized swimming pool. When burned through the rocket’s engines, it produces sufficient thrust to fly to the moon at speeds of up to 24,500mph.

But first, the rollout. As early as Saturday morning, Nasa’s crawler-transporter 2, an enormous tracked vehicle, will start lugging the 5,000-tonne rocket and spacecraft from the vehicle assembly building to the launchpad. The four-mile journey can take up to 12 hours.

Nasa will then work through a preflight checklist. If all goes to plan, engineers will move on to a wet dress rehearsal, loading the rocket with more than 700,000 gallons of propellant, conducting a trial countdown and demonstrating that they can remove the propellant safely.

Any substantial problems would require the rocket to be rolled back to the vehicle assembly building for repairs. In recent days, technicians have been working on a bent cable in the rocket’s flight termination system, a faulty valve used to pressurise the Orion capsule, and leaks in equipment that pumps oxygen into the spacecraft.

The entire process must go smoothly for the mission to launch on 6 February. If technical problems or bad weather intervene, Nasa has identified 14 other dates to launch before mid-April. “We’re going to fly when we are ready,” said Honeycutt. “From launch through the mission days to follow, the crew’s safety is going to be our number one priority.”

After liftoff, the crew will loop twice around the Earth. Before heading to the moon, the Orion capsule will separate from the rocket’s upper stage. The astronauts will then fly the spacecraft manually, using cameras and the view outside the window, to approach and retreat from the jettisoned stage. This will give Nasa a sense of how Orion handles for future Artemis missions where crews will dock and undock in lunar orbit.

For all Nasa’s preparations and the astronauts’ extensive training, the mission could still throw up some surprises. “This is a test flight and there are things that are going to be unexpected,” said Jeff Radigan, Artemis II’s lead flight director.

A final push from Orion’s European service module will send the crew to the moon. The astronauts will travel more than 230,000 miles from Earth, passing around the far side of the moon, before looping back in a giant figure-of-eight trajectory. During the voyage, the crew will practise emergency procedures and test Orion’s radiation shelter, designed to protect them from harmful solar flares.

More than 50 years after humans went to the moon, it is time to get excited again – and perhaps a little nervous. “Every rocket launch is a nail-biter,” Parker said. “We’re putting astronauts on a rocket, and it’s flown only once before, so of course it’s a nail-biter. But I’m confident Nasa will only launch when they are ready.”