Dubbed "Inspiration Mars," the flyby mission would exploit a rare alignment of Earth and Mars that minimizes the time and the fuel it would take to get to Mars and back home again. The astronauts would come within 100 miles of the Martian surface before being slung back to Earth.

"It would be a voyage of around 800 million miles around the sun in 501 days," Tito testified Wednesday at a hearing of the House subcommittee on space. "No longer is a Mars flyby mission just one more theoretical idea. It can be done. Not in a matter of decades, but in a few years."

Tito is a former engineer who made a fortune in investment management and, in 2001, became the first person to pay his way into space, buying a seat on a Russian rocket. Now he's pitching Inspiration Mars as a national priority for the United States. Grab this rare chance to go to Mars quickly or risk seeing China or Russia get there first, he told members of Congress.

Tito mentioned a backup plan that would offer Inspiration Mars four more years of development time. Another alignment of planets in 2021 offers a second chance to go to Mars fairly quickly, but the journey would last 80 days longer and require that the astronauts fly much closer to the sun, within the orbit of Venus, in one portion of the trip. That would add to the already considerable radiation hazards.