Dennis Tito, the American entrepreneur who paid $20 million in 2001 for a trip to the International Space Station, spoke before a House subcommittee on space today to outline his plans for reaching Mars. According to Tito, the "Inspiration Mars" endeavor will be a fly-by mission that'll take two astronauts 808 million miles from Earth to Mars and back again in 501 days. And he'll need more than $1 billion to do it.

"No longer is a Mars fly-by mission just one more theoretical idea. It can be done."

The plan works within a narrow timeline that takes advantage of a rare alignment in Earth and Mars' orbits. According to Tito's written testimony, the launch will need to take place between Christmas 2017 and January 5th, 2018 to ensure a speedy trip. So to pull that off, Inspiration Mars will need complete cooperation from NASA — the two-man crew aboard the Inspiration Mars' commercial craft will need the space agency's huge Space Launch System (SLS) rocket to propel them there. The SLS rocket is still under development.

This plan comes at a premium, however, and nothing is assured just yet. Tito told the committee that he expects private donors to give $300 million in funding, and needs the government to pony up $700 million. NASA, for its part, issued a careful statement in October saying, "The agency will continue discussions with them to see how NASA might collaborate on mutually-beneficial activities that could complement NASA’s human spaceflight, space technology and Mars exploration plans. The agency has not made any commitments to Inspiration Mars related to launch vehicles." Having just weathered a government shutdown, it can be assumed the agency is in no rush to fund anything just yet.

Tito has been pushing for a manned mission to Mars since February, and there's still time for the plan to get off the ground. Once all the details concerning funding and development are ironed out, it will fall on NASA to determine if a launch in Tito's proposed window is possible.