Vowing to inspire “all Americans,” the world’s first space tourist, Dennis Tito, is set to announce a plan Wednesday for a “high risk” human mission to Mars. It would launch, by necessity of orbital mechanics, in January 2018.

Now all Tito needs is a billion dollars, give or take. And a big rocket. And a spaceship.

“It’s not nuts,” said one of Tito’s team of aerospace industry advisers ahead of an afternoon press briefing in Washington. “This is possible.”

The “Mission for America” would be a two-person, budget-class fly-by of the red planet. There will be no landing. No footprints and flags in ruddy soil, no rock-grabbing, no search for fossils.

This is strictly a blink-and-you-miss-it trip to Earth’s neighbor and back again. The 501-day journey would be about the quickest available with current rockets.

Only celestial harmony makes such a plan feasible: A once-every-15-years alignment of Earth and Mars. With the two planets’ orbits pinching as close as they ever do, a so-called low-energy trajectory could shoot a modest craft to Mars and back with minimal fuel.

Tito, 72, won’t fly the mission. Instead, he will send a man and woman — preferably married — to fairly represent humanity, said a person familiar with the plan who asked for anonymity because the public announcement has not yet been made. . .