Scientists have rovers on Mars, sent probes to Venus and Mercury, rocketed a craft that whizzed past Pluto and even landed a probe on a comet. But even with this stellar record, getting a man-made probe to another solar system seems impossible. Even Voyager 1, which is already 11 billion miles from Earth, won’t come close to another star system for 40,000 years.
Even so, Russian billionaire and internet entrepreneur Yuri Milner has a plan. On Tuesday, Milner, accompanied by Nobel-prizing-winning physicist Stephen Hawking, announced that he is investing 100 million dollars into his Breakthrough Starshot Project, with a goal of sending a fleet of probes to Alpha Centauri, our nearest neighboring star.
“Earth is a beautiful place, but it might not last forever,” Hawking says in a press release. “Sooner or later we must look to the stars.”
Milner hopes other philanthropists, scientists and governments will join the initiative. So far, Facebook’s Mark Zuckerberg and Hawking both will join Milner on the board of directors. Pete Worden, former director of NASA’s Ames Research Center, has signed on as executive director. Other space luminaries like physicist Freeman Dyson, astronaut Mae Jemison and astrophysicist Saul Perlmutter are advising the project, according to the press release.
The idea is to send a mothership full of nano-bots into high-altitude orbit. The ship would then release hundreds of the bots, dubbed “starchips.” Each bot, which costs roughly as much as an iPhone, is about the size of a postage stamp and is attached to very thin sails a few meters wide, Ross Anderson writes for The Atlantic.
But to propel the bots into hyper drive will require energy from a ground-based laser, which would blast a beam of light at the tiny bots' sails for two minutes, accelerating the bot to one-fifth the speed of light, roughly 100 million miles per hour. At that rate, the swarm of light-propelled probes could reach Alpha Centauri, 4.37 light years away, in about 20 years.
But why Alpha Centauri? The system is not just the closest system, but is a group of three stars: Alpha Centauri A and B, which circle each other, and Proxima Centauri, which may orbit the other two stars. Researchers also think an Earth-like planet may orbit Alpha Centauri B.
Milner tells Anderson that each probe would have a two-megapixel camera and star finders to help guide it toward any planets in the habitable zones around the Alpha Centauri A and B.
While the mission is intriguing, the five- to ten-billion-dollar price tag is a problem. The mechanics will also take a while to sort out. “There are about 20 key challenges we are asking the world’s scientific experts to help us with—and we are willing to financially support their work,” Pete Worden tells The New York Times.
The biggest sticking point is the laser, which would need to generate 100 gigwatts of power, about 100 times the output of a nuclear power plant, to accelerate a single probe. The tiny probes will also need to survive 60,000 times the pull of gravity during their acceleration.
Still, Milner says he thinks technology will advance to the point where this is possible, targeting the Atacama Desert for the laser array. “If you have a reasonable sized battery, and a reasonable sized array, and a reasonable sized power station, you probably can do one shot a day,” Milner tells Anderson. “And then you recharge and shoot again. You can launch one per day for a year and then you have hundreds on the way.”
Even the program’s supporters question whether it will get off the ground in its current form. Freeman Dyson tells Anderson that he worries the probes might get ripped to shreds by dust, rocks, ice or something else that may fill interstellar space. He also worries that it will be difficult to build a sail thin and strong enough to survive blast from a 100-gigawatt laser array.
Milner, for his part, has relatively realistic expectations for the project. He knows it will take a lot of time and money to figure out the technology before the mission can even begin. “That’s what the $100 million is for,” he tells Anderson. “It’s to do extensive research into all of these challenges, and try to convince ourselves that this is possible in the lifetime of a single generation.”