After announcing Maezawa to reporters, Musk was asked whether the planned mission would inspire him to take part.

“As far as me going? I’m not sure,” Musk said.

“[Maezawa] did suggest that maybe I would join [him] on this trip ... I don’t know ...”

Then Maezawa interrupted him to say: “Oh yeah, yeah – please, please ...” 

Musk replied: “All right. Maybe we’ll both be on it.”

However, it was unclear if the entrepreneur was being serious.

SpaceX’s first moon mission is slated to launch aboard the 38-storey-high rocket in about 2023.

Engineers are currently building a prototype.

Tentative plans show that the flight could last about six days and will see the huge rocket – which is being designed to eventually colonise Mars – travel to within about 30 miles (about 50km) of the lunar surface before returning to Earth.

Maezawa, Japan’s 18th richest person, who is the founder and CEO of online fashion retailer Zozo, bought all of the seats for passengers on the spaceship for an unknown sum.

He plans to invite a diverse group of artists to fly with him as part of a project he has dubbed #dearmoon, which will involve them creating work inspired by their lunar journey.

Although it is unclear how much he paid to become the first space tourist to travel to the moon and back, Musk says Maezawa is “paying a lot of money that would help with the ship and its booster”.

SpaceX had been in talks with the Japanese billionaire about the moon mission since at least 2017, although an earlier plan had involved the crew flying in a much smaller Crew Dragon capsule on top of another of the company’s rockets, the Falcon Heavy.

However, the Big Falcon Rocket is much larger and more powerful, and – because of its ultimate aim, of travelling to Mars to colonise the planet that is just over half the size of the Earth – highly ambitious.

If the #dearMoon mission is successful – something that Musk has described as “very dangerous” – Maezawa and his companions (possibly even Musk, himself) will become the first people to travel to the moon since Nasa’s Apollo 17 mission.

The trio of US astronauts Gene Cernan, Ronald Evans and Harrison Schmitt returned from the last lunar landing in December 1972.

Musk says that SpaceX still only has “some concepts” for how the interior design of the moon mission’s spaceship and crew quarters will look.

However, he thinks the week-long lunar voyage – instead of a six-month journey to Mars – will leave plenty of time for some fun.

“What is the most fun you can have in zero G [gravity]?” Musk says of the spacecraft’s interior design plans. “We’ll do that.”

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This article originally appeared on Business Insider.