Yuri Milner is spending $100 million to prove out laser pushed nanosails that would reach 5% of lightspeed

Milner has an estimated networth of $3.1 billion. In 2012, Milner established The Breakthrough Prize, a set of international awards recognize three fields: Fundamental Physics, Life Sciences and Mathematics.
In July 2015, Milner launched the Breakthrough Initiatives, a major new scientific program investigating the question of life in the Universe. He announced the initiatives at the Royal Society in London, alongside Stephen Hawking, Martin Rees, Frank Drake, Geoff Marcy and Ann Druyan.
Two initiatives have been announced so far. The first, Breakthrough Listen, will invest $100 million over 10 years in the most comprehensive and sensitive search ever undertaken for evidence of civilizations beyond Earth.
Milner, joined Stephen Hawking in Manhattan, where the pair will announced Starshot, a $100 million dollar research program, the latest of Milner’s “Breakthrough Initiatives.” (Mark Zuckerberg will serve on Starshot’s board, alongside Milner and Hawking.) With the money, Milner hopes to prove that a probe could make the journey to Alpha Centauri in only 20 years.
Milner wants his $100 million to fund research that will culminate in a prototype of a probe that can beam images back to Earth. He told me the images would arrive less than 5 years after the probe reached the star.
There are no official specs yet, but Milner said the probe would have a two-megapixel camera, along with star-finders to help it get its bearings, after it boots up on the approach to Alpha Centauri. The probe will target one of the system’s two sunlike stars.
It will be aimed at a planet (or planets) in the star’s habitable zone, the temperate region where oceans don’t boil or freeze, but instead flow, nurturing the kind of complex chemistry that is thought to give rise to life.
Milner envisions a sail that’s only a few meters wide. Picture a thin disc about the size of a round picnic tabletop. It would have miniaturized electronics onboard, including a power source, cameras, photon thrusters for navigation, and a laser for communication.
Some of this kit would be bundled into the disc’s center, and some would be distributed through the rest of the sail. But it would all be a single unit: If you saw it streaking by, it would look like a flat, round sheet of reflective material.
Milner wants to launch a small “mothership,” filled with hundreds of these thin, disc-like probes. (He thinks each probe can eventually be manufactured at roughly the cost of an iPhone.) Once the mothership reaches orbit, it would release one probe per day. The probe would exit the larger spacecraft, and use its photon thrusters to position itself in the path of a ground-based laser beam.
The laser would be located somewhere in the Southern Hemisphere. “You need to put it high in the mountains,” Milner told me. Too much air or moisture, and the laser will be distorted on its way out of the atmosphere. “An interesting place would be the Atacama desert in Chile,” he said. 
Milner hinted that the atmospheric turbulence problem would be solved with adaptive optics.
“It’s the mass that gets you every time,” said Andreas Tziolas, the director of Icarus Interstellar, a group that researches star travel. “Every time I’ve seen a beam-propulsion study, they quote the size of the sail without any physical or mechanical support.
They work so hard to build something the size of a table that weighs one gram, but then they add a support, like a wire or a piece of steel, and it goes to 10 kilograms.”
Tziolas did say there was interesting work being done in Japan, involving flexible sail-like materials that stiffen when charged, eliminating the need for a heavy support system.
Milner said he’s imagining a spacecraft that weighs a mere few grams. He said the sail would be exceedingly thin, perhaps only a few hundred atoms.