Billionaire Russian investor Yuri Milner and British cosmologist Stephen Hawking on Tuesday announced an ambitious new space initiative for a mission to Alpha Centauri, the nearest star system to Earth.

Milner and Hawking are spearheading the "Breakthrough Starshot" team of scientists working on the bold research program to create a fleet of super-compact, ultra-light space vehicles or "nanocraft."

The goal is to send the light-propelled mini space vehicles - each no bigger than a cell phone - to Alpha Centauri, which is 4.37 light years away, or 25 trillion miles, from Earth.

They estimate it could take about 20 years to reach the star system from the time of the launch - rather than the 30,000 years it would take with today's fastest spacecraft.

"Space travel as we know it is slow. How do we go faster and how do we go further? How do we make this great leap?" Milner, who is planning to initially commit $100 million to the project, told a press conference in Manhattan.

"For the first time in history, we can do more than just gaze at the stars. We can actually reach them," added the 54-year-old Russian philanthropist, whose fortune is estimated at $2.9 billion by Forbes.

"It is time to launch the next great leap in human history."

'Interstellar sailboat'
Milner - one of the original investors in Facebook - said the team hoped to send a super light robotic spacecraft streaking through space at 60,000 kilometers (faster than 37,000 miles) per second - about 20 percent the speed of light.

The initiative will work by creating a giant laser array to propel the mini-probes - which would deploy micro-sails - toward a given star, creating what Milner likened to an "interstellar sailboat."

"The Breakthrough StarChip concept is based on technology either already available or likely to be available in the near future. But as with any moonshot, there are major engineering problems to solve," Milner cautioned.

Hawking noted: "I believe what makes us unique is transcending our limits."

Milner said that he will contribute $100 million from his own pocket for the project, which could cost as much as $10 billion before it is fully realized.

"It's very clear that it's a non-profit initiative," he joked, acknowledging that the chance for success and the final cost were unclear.

Milner, Hawking and Facebook founder Mark Zuckerberg will sit on the project's board.

Search for life
A team has already been working on the endeavor for a year, Milner said.

Initial research results indicate that the giant laser array - the "light beamer" - would require about 100 gigawatts, roughly the energy needed to launch a space shuttle, said Avi Loeb, a professor at Harvard University and a project member.

"When there is a vision for a grand project like this one, just like the vision that JFK had in the 60s, it lifts many bolts," said Loeb in a nod to former US president John F. Kennedy, whose vision it was to land a man on the moon.

Milner and Hawking have teamed up previously.

Last July, Hawking launched a massive search for intelligent extraterrestrial life in a $100-million, 10-year project to scan the heavens funded by Milner.

Milner said at the time that the "Breakthrough Listen" initiative would be the most intensive scientific search ever undertaken for signs of alien civilization.

The project, they said, would use some of the biggest telescopes on Earth, searching far deeper into the universe than before for radio and laser signals.

One aim of the mission to Alpha Centauri is also to look for signs of extraterrestrial life, Loeb said.

And what might those living creatures be like?

"Judging by the election campaign, definitely not like us," joked Hawking - who is wheelchair-bound and uses a computerized voice system to communicate - in reference to the drama-filled race for the White House.