A man and a woman will make a privately funded, 501-day trip to Mars and back in 2018 under a plan unveiled Wednesday.

The Inspiration Mars Foundation plans to launch the carefully selected middle-aged American couple into space on Jan. 5 of that year, U.S. billionaire businessman Dennis Tito, chair of the new non-profit organization, told a news conference in Washington.

The space voyagers will come within 160 kilometres of the surface of the Red Planet, then swing around and return to Earth.

"I'm just really excited about this," said Tito. "This is a challenging but attainable goal, advancing human experience and knowledge. Now is the time."

Tito lamented NASA's lack of progress in human space flight since the moon missions 40 years ago.

U.S. President Barack Obama said in 2010 that he expects to be around to see humans land on Mars. (NASA/JPL/Cornell)U.S. President Barack Obama said in a 2010 speech that by the mid-2030s, he envisioned being able to send humans to orbit Mars and then return them safely to Earth, and he expected to be around to see humans land on Mars after that.

However, Tito said, "I'm going to be 95 years old. I don't want to wait."

He added that the 2018 launch date represents a window of opportunity when the journey from Earth to Mars will be the shortest, due to their alignment with one another. The next such opportunity won't come until 2031.

Tito personally funding project for 2 years

In order to move things forward, Tito said he has committed to personally funding the first two years of the project, until the end of 2014. He emphasized that it's not a commercial mission, and he doesn't expect to get rich from the venture.

"Let me guarantee you, I will come out a lot poorer as a result of this mission. But my grandchildren will come out a lot wealthier through the inspiration that this will give them."

He hopes to raise the rest of the money from private donors, charitable organizations, selling media rights and selling data to NASA.

He did not disclose how much it will cost, but said it will be comparable to a space flight into low-Earth orbit because the mission doesn't include any complications such as docking or entering Mars's atmosphere. Its course will be set as it leaves Earth so that no "propulsive manoeuvres" will be required once it's left Earth's atmosphere, and it will rely on Mars's gravity to turn it around for its return to Earth.

Tito said the mission will largely use existing technology. The components include a Canadian-made inflatable habitat unit that will be deployed after the spacecraft leaves the Earth and detach before it re-enters the Earth's atmosphere on the return journey.

However, the team still needs to figure out how to deal with challenges such as:

• Dangerous levels of radiation.
• Life support systems required on such a long space trip.
• Making sure the space vehicle can safely re-enter Earth's atmosphere despite extremely high speed.

The foundation will get help from NASA to solve some of those problems.

Tito, a former NASA rocket scientist and founder and chief executive of the investment management firm Wilshire Associates Inc., became the world's first space tourist when he paid an estimated $20 million US to take a Russian Soyuz spacecraft up to the International Space Station in April 2001.

However, he said he will not be one of the people on this journey, as the requirements will be too high.

Jane Poynter, president and chairwoman of Paragon Space Development Corporation, the company developing the life support systems for the mission, said at the news conference that the selection of the crew will be "rigorous to make sure they are resilient and can maintain upbeat and happy attitude in face of adversity."

They will spend a year and half with only each other for company in just 17 cubic metres of living space, breathing recycled oxygen, drinking water recycled from their sweat and urine every two days and eating food rehydrated with that recycled water.

Poynter said it's important that the crew members be a "trusted, tested" couple so they will be able to support each other through hard times.

And she said it's important that they be a man and a woman so that both boys and girls will see themselves reflected in the crew and be inspired.

"Inspiration is the namesake of this mission and of this foundation," she said.