Mikhail Metzel / AP file Millionaire spaceflier Dennis Tito flashes a thumbs-up sign during final preparations for his 2001 flight to the International Space Station. Now Tito is reportedly contemplating a mission to Mars.

By Alan Boyle,

Science Editor, NBC News

Dennis Tito, the millionaire investment whiz who became the first paying passenger to visit the International Space Station in 2001, has worked out a plan to send two astronauts to Mars and back without stopping. However, the privately backed 501-day flight would have to be launched in 2018 — or wait until the 2030s.

Details about the Red Planet flyby are trickling out in advance of a Washington news conference next week.

First word of the venture came out in a media advisory passed along by the SpaceRef website on Wednesday. The advisory from the Texas-based Griffin Communications Group describes a "Mission for America" that would capitalize on a favorable orbital opportunity to launch a round-trip mission to Mars in January 2018.

The advisory includes an invitation to attend a news conference at 1 p.m. ET Feb. 27 at the National Press Club in Washington, issued by the Inspiration Mars Foundation, which is described as a "newly founded nonprofit organization led by American space traveler and entrepreneur Dennis Tito."

Tito, a former rocket engineer, made his fortune as the founder of Wilshire Associates, a multibillion-dollar investment firm based in California. He made history in 2001 when he paid a reported $20 million for a ride aboard a Russian Soyuz spacecraft to the space station. At the time, the eight-day round trip was highly controversial and required changes in the policies governing space station operations. Since then, six other high-net-worth individuals have taken similar flights with little or no controversy. The current published price for such flights is upwards of $40 million.

In the nearly 12 years since his flight, Tito has taken a relatively low public profile in the private-sector spaceflight industry. Meanwhile, other millionaires and billionaires, ranging from SpaceX's Elon Musk to Amazon.com founder Jeff Bezos to Microsoft co-founder Paul Allen, have been in the vanguard.

Little is known about the Inspiration Mars Foundation, and the name doesn't turn up in databases for tax-exempt nonprofit organizations. The Internet domain names "InspirationMars.com" and "InspirationMars.org" were registered anonymously last October. But other than that, the only information that could be gleaned about Inspiration Mars comes from the media advisory, which says it's "committed to accelerating America's human exploration of space as a critical catalyst for future growth, national prosperity, new knowledge and global leadership."

"This 'Mission for America' will generate new knowledge, experience and momentum for the next great era of space exploration," the advisory said. "It is intended to encourage all Americans to believe again, in doing the hard things that make our nation great, while inspiring youth through Science, Technology, Engineering and Mathematics (STEM) education and motivation."

In addition to Tito, the speakers listed for next week's news briefing include Taber McCallum and Jane Poynter, who are veterans of the Biosphere 2 life-containment experiment and the top executives at Paragon Space Development Corp., which develops life-support systems for spacecraft. Jonathan Clark, a former NASA flight surgeon who now serves as an adviser for several space ventures, is also due to appear. Veteran TV journalist Miles O'Brien, who was once in line to take a trip to the space station, is to serve as moderator.

Update for 10:58 a.m. ET Feb. 21: The media advisory doesn't describe the specifics of the proposed mission, but spaceflight consultant Jeff Foust, publisher of the online NewSpace Journal, has come across information that sheds lots of additional light on Tito's plans. It turns out that Tito is due to give a presentation at the IEEE Aerospace Conference in Montana next month. He and his co-authors discuss the project in a paper prepared for the presentation. Here's a quick rundown of what Foust found:

The mission would involve a flyby of Mars with a free return back to Earth, without stopping. That type of low-energy trajectory requires a special set of orbital circumstances: The presentation says those circumstances exist for the 2018 opportunity but won't repeat until 2031. Two astronauts living in spartan conditions could make the 501-day trip in a modified SpaceX Dragon capsule, launched by SpaceX's yet-to-be-flown Falcon Heavy rocket.

Be sure to read Foust's full item on NewSpace Journal.

The plan seems to be just on the edge of doability. Among the questions that come up: Would the Dragon have adequate radiation shielding for the long-duration, deep-space trip? Can the crew cope with long-term isolation in close quarters, as well as the health effects of an extended zero-G trip? Can the Falcon Heavy truly be ready for a Mars trip in time for the 2018 opportunity? And who's going to pay for all this? Although there's no price tag attached to the plan, doing the mission seems likely to require billions of dollars. Tito may be rich, but is he that rich?

Update for 1:05 p.m. ET Feb. 21: Griffin Communications has confirmed the substance of the media advisory but released no additional information. The logistics for next week's briefing at the National Press Club are still being worked out. It's not yet known whether the proceedings will be webcast.

Update for 6:18 p.m. ET Feb. 21: A few more tidbits have trickled out: Even though the IEEE paper focuses on the SpaceX Dragon and Falcon Heavy, that doesn't mean SpaceX's participation in the project is a sure thing. The astronauts could ride on any of a range of space vehicles. One thing is for sure, however: Tito, who is now 72 years old, will not be making the spaceflight himself.

Although the IEEE paper casts the "Mission for America" as a private-sector effort, NASA would play a supporting role in technology development. A source who has been told about Tito's plans said the 2018 effort was not meant to provide competition for NASA's exploration effort, but instead provide support. NASA is working on a long-range program to send astronauts to a near-Earth asteroid in the mid-2020s, and to Mars and its moons in the mid-2030s.

The source was not authorized to speak publicly about Tito's plans, and thus spoke with NBC News on condition of anonymity.

More about Mars ambitions:

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

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