The self-made millionaire who paid for his own trip to the International Space Station a decade ago as the world's first orbital tourist wants to send a two-person crew on a 501-day flyby of Mars in 2018, skimming a mere 100 miles above the red planet's surface before looping back for a high-stakes return to Earth.

He just needs the money, spacecraft, launcher and two volunteers to mount the private -- and daring -- adventure.

An artist's concept of the spacecraft. Credit: Inspiration Mars Foundation

Dennis Tito, who captured headlines in a controversial April 2001 flight to the station aboard a Russian Soyuz on his own dime despite NASA objections, has created the nonprofit Inspiration Mars Foundation.

"Sending humans on an expedition to Mars will be a defining event for humanity as well as an inspiration to our youth," the team says in its feasibility study.

"Social media provides an opportunity for people to meaningfully participate in the mission, likely making this the most engaging human endeavor in modern history. The mission will address one of the most fundamental technical challenges facing human exploration of space, keeping the humans alive and productive in deep space."

The goal would use the relatively rare alignment of Earth and Mars to send a spacecraft on a so-called "free-return" trajectory, essentially flying a manned boomerang around the neighboring planet and returning home without needing any major propulsion to get back.

But there will be no way to abort the mission once departure from Earth occurs, leaving the astronauts with only their own wits and ingenuity to fix troubles along the way.

Taber MacCallum, the chief technical officer for Inspiration Mars and CEO of Paragon Space Development Corp., said it's "the kind of risk America used to be able to take."

"That's the kind of bold thing we used to be able to do, we don't do that anymore," he said. "We've shirked away from risk. I think just seriously contemplating this mission recalibrates what we believe is a risk worth taking for America."

Reliability of the closed-loop life support system, limited knowledge of deep-space radiation and the high-speed re-entry are the three riskiest parts of the endeavor, officials said.

Lifting off on Jan. 5, 2018 atop a high-performance rocket such as the existing United Launch Alliance Delta 4-Heavy or one in development like SpaceX's Falcon Heavy, the 10-ton capsule and its inflatable habitat will leave Earth for mankind's first human journey to Mars.

It will take 227 days to transit across interplanetary space, braving the dangers of radiation, prolonged exposure to microgravity, the worries of hardware breakdowns and the psychological impacts of being cooped up in the cramped craft for so long.

Bringing all the water and oxygen in big tanks would be prohibitive, so the crew will drink the same water and breath same oxygen over and over again through recycling urine and sweat and scrubbing carbon dioxide. There will be no need for spacewalks and controllers will rely on the astronauts instead of largely automating the spacecraft.

About 3,000 pounds of dehydrated food would be loaded aboard to feed the crew for a year-and-a-half in the spaceship that is roughly the size of a small Winnebago.

The spacecraft will be roughly the size of a Winnebago. Credit: Inspiration Mars Foundation

Calling the mission "austere" and "barebones" to keep costs down and the hardware simplistic, the foundation says it won't have to follow all of NASA's strict air- and water-quality rules. And they will rely on a mechanically-inclined crew to make repairs as necessary during the trek.

Tito is self-funding the project for the first two years, ensuring it gets a solid footing until external financial support can be found and pumped into the mission. Engineering work on "critical-path items" started last month.

If the early 2018 launch window is missed, the next opportunity for the free-return trajectory won't come around again until 2031.

Tito, now 72, holds a master's degree in engineering and worked early in life at the Jet Propulsion Laboratory designing trajectories for flybys of Mars and Venus using robotic Mariner probes and then entered the investment industry where he made made millions, also added that he would not be taking the trip himself.

"It will be quite a crew selection process," he said.

He wants the two-person, middle-aged crew to include a man and woman, preferably married, to take the journey that he calls a "sea change" to move beyond only talking about human expeditions to Mars into real action.

But Homer Hickham, author or "Rocket Boys/October Sky," fired back with a Twitter posting: "A married couple in a bathroom for 501 days? I love my wife but rather take my cat and some good books."

Jon Clark, a former NASA flight surgeon whose wife, Laurel Clark, died in the 2003 Columbia disaster, said exhaustive screening procedures will be used to select candidates with excellent health, technical competence and psychological stability.

The crew must accept the personal risks such a voyage would entail, including increased chances of developing cancer from the radiation they would experience. Clark said estimates put the excess cancer mortality rate over a lifetime "in that ballpark" of around the three-percent limit NASA has for its own missions.

"So, the real issue here is understanding the risk in an informed capacity. The crew would understand that. Ultimately, that is going to be the decision based on that informed consent," Clark said.

The 2018-2019 timeframe, however, will coincide with the 11-year solar minimum providing the lowest solar radiation exposure, the foundation said.

Still, the duo would give humanity its first adventure away from Earth and its moon, which was visited from 1969 to 1972 by Apollo astronauts.

"When nations boldly follow opportunities, rooted in curiosity and guided by technological innovation, they grow, prosper, learn and lead. And this is what makes a nation great," said Tito.

"Human exploration of space is a critical catalyst for our future growth and prosperity," he added. "This is 'A Mission for America' that will generate knowledge, experience and momentum for the next great era of space exploration. It will encourage and embolden all Americans to believe, again, in doing the hard things that make our nation great, and inspire the next generation of explorers to pursue their destiny through STEM education."

In the foundation's unveiling Wednesday in Washington, Tito cited private individuals, charitable organization, charging NASA science data fees for experiments run during the mission and even selling lucrative media rights would fund the mission.

"Dr. Phil solving their marital problems, it will be great," Tito quipped.

Although unwilling to disclose how much he is spending or how much the mission will cost in all, Tito said the project would be "much, much lower" than the conventional wisdom on Mars mission price tags and more in line with low-Earth-orbit flights.

"Compared to, say, the landing missions, even if you could contemplate what an overall landing mission to Mars might cost or even in today's dollars what the Apollo missions cost, you're talking a factor of a hundred (less). This is really chump change."

"It uses low-Earth-orbit architecture and we're just adapting it, in effect, to a very large Earth orbit that ... just happens to go out pretty far," Tito said. "But you're really flying this mission without a propulsion system on the spacecraft, it's in the most simple form."

An artist's concept of the flyby specifics. Credit: Inspiration Mars Foundation

After swinging around Mars on Aug. 20, 2018, going behind the planet on the "dark side" at closest approach, the spacecraft will head for home on a 274-day cruise without requiring any maneuvers and major propulsive engine firings to commence the trip back.

Then comes the harrowing re-entry, plowing into the atmosphere at a staggering 31,800 mph, an unprecedented speed for a manned spacecraft.

The foundation has signed a Space Act Agreement with NASA's Ames Research Center in California to work on a heat shield capable of withstanding the fiery plunge toward a landing.

Builders of the spacecraft could include the SpaceX Dragon, Boeing's CST-100 capsule or possibly Lockheed Martin's Orion. Bigelow's inflatable habitat or the Italian-made cargo modules from the Cygnus supply ships could be added to the spacecraft to give the crew added room.

Mission planners are considering a 1,200-cubic-foot spacecraft, half of which would be filled with food, water tanks, life support gear and spare parts. The crew would have about 600 cubic feet of living space.

Landing would be May 21, 2019, just months shy of the 50th anniversary of man's first walk on the moon by Neil Armstrong and Buzz Aldrin and 500 years since Ferdinand Magellan set sail on the first expedition to circumnavigate the Earth.

"There are lots of options and ways to get this done," MacCallum said. "We have an amazing industrial base and it's about time America stood up and proved to the rest of the world we've got, bar none, the best industrial base in the world. Let's show it to them. Let's do this mission."