At a Monday briefing, SpaceX revealed that two people have already paid the company to fly them around the moon on a Falcon Heavy space rocket flight in 2018.

“We are excited to announce that SpaceX has been approached to fly two private citizens on a trip around the moon late next year. They have already paid a significant deposit to do a moon mission. Like the Apollo astronauts before them, these individuals will travel into space carrying the hopes and dreams of all humankind, driven by the universal human spirit of exploration. We expect to conduct health and fitness tests, as well as begin initial training later this year,” the press release read.

Although the amount was not disclosed, Elon Musk has confirmed that the cost for an around-the-Moon mission could be around or more than the cost of sending a crew from Earth to the International Space Station. The Verge said that based on historical figures and market conditions, it could be at USD74.7 million, minimum.

Musk, who heads SpaceX as CEO, will now be in competition with NASA’s plans to do a separate “EM-1” crewed moon trip for its SLS rocket, which will reportedly happen also in the same year, Buzzfeed reported.

But will SpaceX be able to make it? Space law expert Micheal Listner told the trending news site that unless they get their FAA license cleared off for the lunar mission, SpaceX faces an uphill battle even it develops the Falcon Heavy rocket and Dragon capsule on time for the launch.

Scott Hubbard, researcher in the Stanford University Department of Aeronautics and Astronautics, told Space.com that it could be possible in principle, but the firm has to address technical questions first.

He asks, "The key technical issue will be demonstrating life support in the Dragon for two people for the duration of the mission. With reasonable margins, the length of mission will be longer than planned for commercial crew. The key programmatic issue is level of risk: Is it understood? Has it been mitigated sufficiently?"