It's a road trip that could test the best of marriages: Earth to Mars.
A tycoon announced plans Wednesday to send a middle-aged couple on a privately built spaceship around the red planet and back to Earth.
It would mean 501 days of no-escape togetherness in a cramped capsule half the size of an RV (caravan).
The voyage to Mars and back would be a cosmic no-frills flight that would take the husband-and-wife astronauts as close as 100 miles to the planet, but it would also mean being cooped up for 16 months.
The private, nonprofit project called Inspiration Mars, will get initial money from multimillionaire investment consultant Dennis Tito, the first space tourist.
The team would not say how much the overall flight would cost, but outsiders put it at more than $1 billion.
Tito dodged questions about how much he would personally contribute.
"This is not a mission that, if it's successful I'm going to come out to be a lot wealthier," he said, "Let me guarantee you, I will come out a lot poorer as a result of this mission. But my grandchildren will come out a lot wealthier through the inspiration that this will give them."
The organizers hope to raise the rest through donations, advertising and media partnerships.
NASA will not be involved, but officials at the agency said they are eager to collaborate.
Even though some of the hardware hasn't even been built, Tito said he is confident everything will come together by 2018 with no test flights.
The project's backers intend to use a private rocket and space capsule and some kind of habitat that might be inflatable, employing an austere design that could take people to Mars for a fraction of what it would cost NASA to do with robots, Tito said.
The crew members will have no lander to go down to the planet, and no spacesuits to go out for any spacewalk.
They will have minimal food and clothing, and their urine will be recycled into drinking water.
As to why the couple would be married, MacAllum said if it is a man and a woman on such a long, close-quarters voyage, it makes sense for them to be married.
They would give each other the emotional support that will probably be needed when they look out the window and see Earth get smaller and more distant, MacAllum said.
Tito also described the mission as a distinctly American one.
He did not speculate about collaboration with other space agencies or private groups, and made it very clear he wanted to "beat China to Mars."
"Wouldn't I want to do that? Wouldn't I want America to do that? Wouldn't you want America to do that? How many people don't want America to do that?" Tito said to applause from the crowd.
Both Tito and MacAllum drew comparisons to NASA's Apollo program of the 1960s, which put a man on the moon.
MacAllum said the project received a donation from a six-year-old, who said he wanted to be one of the first to contribute.
"The note said that he is going to watch this press conference with his father, 'because this is my Apollo'" MacAllum said, appearing to choke up.
The project aims to capitalize on the once-in-a-generation close approach of the two planets' orbits.
The timeline for the 501-day mission is set out in a technical paper to be presented next month at a scientific meeting.
It calls for a launch on Jan. 5, 2018, a Mars flyby on Aug. 20, 2018, and a return to Earth on May 21, 2019.