Pushed by a laser beam: Can Breakthrough Starshot reach Alpha Centauri?
It’s called Breakthrough Starshot. It’s an ambitious name for a remarkably ambitious project.
It’s the brainchild of Yuri Milner, a Russian philanthropist and Internet entrepreneur, who, together with a team of prominent astronomers and cosmologists, plans to send a fleet of robot spacecraft no bigger than iPhones to Alpha Centauri, the nearest star system, 4.37 light-years away, and to report back on what they find, maybe even some forms of extraterrestrial life. Hello ET?
Under their plan, a rocket would deliver a “mother ship” carrying a thousand or so small probes to space. Once in orbit, the probes would unfold thin sails and then, propelled by powerful laser beams from Earth, set off one by one like a flock of migrating butterflies across the universe. Milner announced the project, which may take up to 20 years or more to come to fruition, with an initial commitment of $100 million for research and development.
The laser is the most intimidating and expensive of the challenges. It would have to generate 100 gigawatts of power for the two minutes needed to accelerate the butterfly probes to a fifth of the speed of light (yes, that would be an astounding 37,256 miles per second) and would subject its tiny innards to 60,000 times the force of normal gravity. That is about as much energy as it takes for a space shuttle to lift off and about 100 times the output of a typical nuclear power plant.
To achieve that energy would require an array about a mile across combining thousands of lasers firing in perfect unison. Moreover, to keep the beam tightly focused on one probe at a time would require an adaptive optics system that compensated for atmospheric turbulence — something astronomers know how to do over a span of 10 meters, the size of a big telescope mirror now, but not over a mile.
Posing another challenge is the design of the sails, which would have to be very thin and able to reflect the laser light without absorbing any of its energy. Absorbing as little as one part in 100,000 of the laser energy would vaporize the sail.
Alpha Centauri is the closest star system to our own, and there might be planets in the system. So, it is an attractive target for the mission. The star system, which looks to the naked eye like one star, actually consists of three: Alpha Centauri A and Alpha Centauri B, which circle each other, and Proxima Centauri, which may be circling the other two. In recent years, astronomers have collected data suggesting the possibility of an Earth-size planet orbiting Alpha Centauri B.
Like any ambitious, challenging project, huge hurdles and issues lie ahead. How do you coordinate that huge laser field and focus the beam(s) to power a vehicle so small? How do you avoid vaporizing those small vehicles with the power of the laser? How do you generate the enormous energy necessary to fire the lasers into space?
Can the computers embedded in the vehicles withstand the 60,000 g-force of immediate acceleration to 37,256 miles per second? With no propulsion system on board the vehicles, how would you redirect their flight if they go off course? With 4.37 light years to traverse, a minute deviation in the course early on would mean it would end up billions of miles away from the target at the end of the journey.
Despite all the challenges that lie ahead, it is a wildly innovative, imaginative and, terrifically exciting venture. The project will require the convergence of many disciplines: science (astrophysics, nanotechnology, and thermodynamics) combined with laser propulsion engineering, microcomputers, and innovative guidance systems, all financed by a bold and imaginative venture capitalist willing to put some of his vast fortune at risk in a daring bid to reach for the stars in a search for other life in our universe.
All this sounds like the voice-over introduction to an episode of the smash hit television series Star Trek:
Space: the final frontier… to explore strange new worlds, to seek out new life and new civilizations, to boldly go where no man has gone before.
No doubt, this is a venture those Trekkies will be passionate about. They will envision all the interstellar adventures they have enjoyed over the years becoming that much closer to a reality. Why, some of the most devoted Trekkie fans might even come forward to invest in the project.
Surely, the opportunity “to boldly go” 4.37 light years at nearly a “Warp Speed” of 37,256 miles per second, while pulling 60,000 G’s, would be irresistible, even if there are no ETs out there.
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