SpaceX chief Elon Musk speaks during a press conference after the launch of SpaceX Crew Dragon Demo mission.

Who would have imagined that tourists would one day be packing their bags to head to space?

In a new announcement SpaceX plans to send four tourists deeper into orbit than any private citizen before them.

The mission could take place by 2022 and easily cost more than $100 million.

The company signed the deal with Space Adventures, which is based in Washington and served as an intermediary to send eight space tourists to the International Space Station (ISS) via Russian Soyuz rockets.

The SpaceX Dragon spacecraft designed to carry people and cargo to orbiting destinations such as space stations is displayed.

The first of these was Dennis Tito, who paid $20 million for an eight hour stay on the ISS back in 2001.

The last to go was Cirque du Soleil founder Guy Laliberte, in 2009.

The new tourists would be carried on SpaceX's Crew Dragon capsule, which was developed to transport NASA astronauts and is due to make its first crewed flight in the coming months.

"Our goal is to try to get to about two to three times the height of the space station," Space Adventure's president Tom Shelley said.

The ISS orbits at 400 kilometers (250 miles) above Earth's surface, but the exact altitude of the Space Adventures mission would be determined by SpaceX, added Shelley.

At its earliest, it could take place by late 2021, though "probably more likely is sometime in 2022," he said.

The capsule was designed to take astronauts from the surface to the ISS. Just nine square meters in volume, there are no private areas to sleep wash or use the bathroom.

Mission duration will depend on what the customers want, said Shelley.

Weeks of training

Asked about the cost, Shelley replied: "It's not cheap."

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The cost of launching a Falcon 9 rocket is $62 million, according to publicly available figures, then there will be the cost of building a fresh Dragon capsule. Could it exceed $100 million?

"Your assessment is correct, I can't comment specifically on the numbers, but yeah those are the cost components," he said.

"We have a pretty good network of high net worth individuals around the world, many of whom we know are interested in spaceflight," he added.

Unlike space tourism to the ISS, which required six months of training in Moscow, the next mission will need four weeks of participation in the US.

After a gap of 12 years, Space Adventures also wants to send two more tourists to the ISS on board a Russian rocket in 2021.