Stephen Hawking's plan to create a starcraft that can traverse the inky blackness separating us and our cosmic neighbour is fantastically ambitious and filled with lots of "the tech will come" assumptions. But at its core, the technology that Hawking and billionaire Yuri Milner want to use to create the ship is already here. It's just not quite at the level of development that it needs to be. The Breakthrough Starshot is a hypothetical interstellar vessel that essentially comes with two main parts: a super-small, sensor-filled wafer (called a "Starchip"), and a LightSail only a few hundred atoms thick. This teeny craft would be propelled by a 100-gigahertz laser array that would accelerate the Starshot to nearly 20 per cent the speed of light. So in 20 years, we'd be knocking on Alpha Centauri's front door.
The Starchip is the heart and soul of the plan. The idea assumes the continued progression of Moore's Law, the oft-quoted "rule" that the computing power of chips will double every two years. Theoretically, we could eventually fit super powerful computers (along with batteries, sensors and whatever else) into increasingly smaller packages. The law has held up remarkably well since the 1970s, but Intel -- the biggest adopter of Moore's chip guidance -- has shown signs of chip miniaturisation slowing, stretching out Moore's original two-year prediction to 2.5 years.
One of the major issues is that we've reached the limits of silicon. Intel has been developing silicon-germanium chips, but the company still has a way to go before such chips becoming available. And all this equipment needs to weigh less than a few grams. So now we're talking about a far-flung future.
Super tiny satellites, called femto-satellites, already exist, but the Starchip is more analogous to NASA's CubeSats initiative: small satellites that can do increasingly complex science. But these CubeSats are measured in centimeters, rather than the much smaller payload that Starshot aspires to use.
In order for this teeny package of sensors to arrive at its destination 4.3 light years away, you need something to power it, and the project has opted for lightsails. The choice makes sense, since the lightweight material cuts down on weight, requires no chemical thrust and uses a photon's energy and momentum by reflecting light.
The most visible proponent of lightsail technology is the Planetary Society, a citizen organisation that successfully launched its first lightsail in July 2015 and is already working on its second. NASA made a major announcement about its own investigations into solar sailing tech just this week.
The Planetary Society's lightsail is about 4.5 microns thick, about the thickness of a garbage bag. But the Starshot design calls for lightsail material only a few hundred atoms thick. So much like chips and CubeSats, solar sails also need to shrink significantly.
The final challenge is propelling the Starshot up to 20 per cent the speed of light. NASA is already funding work by Phillip Lubin, a physicist at University of California, Santa Barbara. His project, known as the Directed Energy Propulsion for Interstellar Exploration, looks at how lasers could push space-faring vehicles faster than ever before. With this technique, according to Lubin, we could send 100kg satellites to Mars in just three days.
In order to send a craft weighing just a few grams into interstellar space, we would need to amp this laser up to 100 gigahertz to reach the required speeds. Lubin said that any laser capable of doing that could also pulverize earth-bound asteroids (if need be), so we're talking some insanely powerful lasers. Most likely, this would be the biggest barrier to Starshot's lofty goal, mainly because an array of this size has never been built.
But none of these pieces require any kind of theoretical sci-fi unobtainium; everything in the design already exists in some degree of early development. Mostly, these pieces of cutting edge technology just need more time in the oven.
Image: Planetary Society