A new private space company has announced an ambitious plan to send tourists to Moon by 2020.
Golden Spike, named after the final bolt hammered into the First Transcontinental Railroad, will sell each two-person mission for $1.5 billion.
Former Nasa science mission director Alan Stern will serve as CEO, and his advisers will include Nasa shuttle program manager Wayne Hale and Homer Hickam, a former Nasa engineer.
They made the announcement on the 40th anniversary of the lift-off of Apollo 17, the last manned mission to the Moon.
"We could not be able to do this without the many breakthroughs NASA made in inventing Apollo, the Shuttle, the International Space Station, and its recent efforts to foster commercial spaceflight," said Golden Spike Board chairman Gerry Griffin.
The aim is to use existing technology and rockets to power the missions, in order to keep costs down. Each trip will involve four launches - two for its lunar lander, two more to send up crew and cargo.
Golden Spike said its plan has been in the works for more than two years, but admitted many questions remain unanswered.
So far it has not said how it will fund its own work up to the first flights, and hasn't even finalised what rockets it will use to get people to Earth's satellite.
But Golden Spike said it had already begun studies with various companies for the design of its lunar lander, lunar space suits, and lunar surface experiment.
"We're not just about America going back to the Moon; we're about American industry and American entrepreneurial spirit leading the rest of the world to an exciting era of human lunar exploration," Stern said.
Stern told Space.com that his company was "state-of-the-art cool", and said there would be a long line of governments, companies and individuals willing to pay the price.