The next big destination in space travel is Alpha Centauri, the closest stars after our sun, and an ace team of scientists and entrepreneurs wants to send a groundbreaking mission there using a fleet of laser-propelled spacecraft — each no bigger than a postage stamp.
It's the kind of plan that falls into the category of so-crazy-it-just-might-work. And Russian internet entrepreneur and philanthropist Yuri Milner is putting $100 million into research for the project, called Breakthrough Starshot, to see whether that's the case.
"We're talking about doing this within the lifetime of a generation, rather than in a few hundred years like people were thinking," Milner told Forbes. Such pursuits are nothing new for the billionaire investor. Last year he put $100 million toward Breakthrough Listen, an initiative to search for signs of alien life, and $1 million toward a parallel initiative to compose the messages that could be sent to said aliens. He and his colleagues — fellow board of directors members include physicist Stephen Hawking and Facebook founder Mark Zuckerberg — think Breakthrough Starshot could get off the ground in just 20 years.
Achieving interstellar travel is a nearly unprecedented feat. Voyager 1 is the only probe in operation that has reached interstellar space — defined as the region of space between star systems — and it took about 35 years to get there. Its original mission was to explore Saturn and Jupiter, but Voyager kept on trucking, traveling past Pluto and, in 2012, exiting our solar system into the cosmos beyond.
Alpha Centauri, which is actually a system of three stars, makes sense as a destination because it's our neighbor — the cosmological equivalent of peeking over the fence. Proxima Centauri is the closest to Earth, at around 4.22 light years away, while Alpha Centauri A and B, which circle each other, are about 4.35 light years away. Also, tantalizingly, scientists have amassed evidence that there may be a planet with a mass similar to Earth orbiting Alpha Centauri B.
The broad strokes of Breakthrough Starshot go like this: A "mother ship" is launched into space and then deploys 1,000 or so nanocraft, or tiny probes, each equipped with a lightweight, reflective sail that opens once in orbit. Then, down on Earth, an array of powerful lasers fire targeted pulses at each probe. The pressure from the pulses would essentially put wind in their sails, accelerating them in about two minutes to one-fifth the speed of light, or 134 million miles per hour. (Probably only one craft could be given a laser boost each day.) At that rate, the fleet could cruise to Alpha Centauri in 20 years. Or as NPR pointed out, "virtually no time on the scale of interstellar travel." For comparison, a ship powered by the fastest methods currently available would need almost 80,000 years to complete the trip.
The idea behind the large fleet is safety in numbers. The more probes, the more likely one is to make it through the cosmos without running into some bit of matter. Even a particle the size of a grain of sand could be fatal, delivering the same explosiveness upon impact as a pound of TNT. The probes that completed their cosmic journey would take measurements and photographs and relay them back to Earth.
It all may sound improbable, but the Breakthrough Starshot team thinks the idea is on solid footing for several reasons: advances in nanotechnology and lasers, and Moore's law, the golden rule for electronics that essentially holds that computing power doubles every two years.
"Strip an iPhone from its case and interface, and the electronics — including the camera and the communications device — weigh on the order of a gram," Harvard astrophysicist Avi Loeb, chairman of Breakthrough Starshot's advisory board, told Scientific American. "That's almost everything you need for a nanocraft, and we practically have it right now, thanks to the ongoing miniaturization of electronics."
Make no mistake, though; the project team sees many challenges ahead. They have identified 20 major technical obstacles that they're seeking experts' help with solving — chief among them, constructing a laser array that can produce 100 gigawatts of power. That's roughly equivalent to the energy needed for the space shuttle to lift off and about 100 times the output of a typical nuclear power plant, writes The New York Times. Other challenges include preventing the nanocrafts' sails from absorbing too much of the laser's energy and vaporizing, and transmitting signals across trillions of miles of space, once the craft reaches Alpha Centauri. (The team has pledged that all of the research will be published and open access.)
Then there's funding. The entire project could cost between $5 billion and $10 billion. Other investors will be needed.
Milner has marshalled an impressive team to work on the project, which was announced at a news conference earlier this month. Pete Worden, a former director of NASA's Ames Research Center, is the project's director, and among its advisers are a Nobel Prize-winning astronomer; the British astronomer royal (yes, that's a title); a mathematician with the Institute for Advanced Study in Princeton, New Jersey; and the widow of Carl Sagan.
"What makes human beings unique?" Hawking said during the announcement. "I believe that what makes us unique is transcending our limits. Nature pins us to the ground. But I just flew to America. Nature forbids me from speaking. But here I am. How do we transcend these limits? With our minds, and our machines."
Here we go.