The Tito group based its initial calculations on a Falcon 9 heavy rocket for launch. SpaceX, which plans to fly the 27-engine heavy-lift variant of its commercial cargo rocket for the first time this year, says although it does not have an “official relationship” with the Inspiration Mars Foundation,” it “will always consider providing a full spectrum of launch services to interested customers.”

Tito's non-profit foundation is examining a range of options for the launch vehicle, crew capsule and habitat, working under a tight deadline. To cover the overall mission, which Tito says he believes will cost less than the $2.5 billion NASA is spending on the Mars Science Laboratory operation, the foundation will raise funds from industry, individuals and others willing to make “philanthropic” donations to spark interest in the U.S. space program. “I don't think it's going to be a real difficult problem,” he says.

By comparison, NASA officials say a planned 2020 robotic Mars landing mission, using a solar-powered version of the Curiosity rover, is capped at $1.5 billion, with room for $80 million worth of U.S. instruments and perhaps another $20 million in foreign contributions.

At that rate, Tito says, the next free-return Mars-flyby opportunity in 2031 could be seized by China or another spacefaring nation. But even if the obstacles to meeting the 2018 deadline prove too great, he says, “the benefits go to the public,” and NASA can use them in its own deep-space human-spaceflight program later on.