A countdown. Ignition. Channeled tongues of fire push the ground away. A rocket races towards space. This is humanity’s route to the stars.

Or maybe not.    

“It’s completely different.” “It gets you away from the rocket equation.” These are the words of Pete Klupar and Zac Manchester, Director of Engineering and Wafer Designer, respectively, for Breakthrough Starshot, an experimental spacecraft design project with aims no lower than the star Alpha Centauri itself. Klupar and Manchester are part of a team of over thirty of the world’s leading astronomers, physicists, and engineers, bankrolled with a cool $100 million by the Breakthrough Initiatives to design a proof-of-concept spacecraft that can travel to our Solar System’s nearest neighbor within a generation.

Following a year of evaluating speculative technologies, most of which Klupar and Manchester describe as “breaking the Laws of Physics or the Law of Economics,” the Starshot team’s chosen design is something that would seem to violate both categories. Their solution involves a thumbnail-sized “nanocraft” attached to a nanometer-thick, meters-wide “lightsail,” and the world’s largest laser to propel the whole thing along. It’s completely crazy – and yet, scientifically and technically plausible.

The Starshot design relies upon the fact that, in Manchester’s terms, “photons push on things.” Like all particles, they have mass and momentum. The Starshot plan is to generate a concentrated stream of photons that can accelerate the tiny spacecraft, just like wind pushing on a sailboat. Using a 1-kilometer wide, 100 megawatt laser array on Earth focused on the nanocraft’s sail, Klupar claims that the miniature spacecraft will reach 20% of the speed of light.

The laser array...consumes the daily output of a mid-size power plant every two minutes.

In many ways, the mission parameters and scientific basis for Starshot feel like an imaginative fiction. In conversation with Klupar and Manchester, however, it’s clear that their team has devoted the requisite scientific analysis to ensure their efforts thus far are not misplaced. Already, the Breakthrough team has produced a prototype for the spacecraft (though Klupar cautions this is little more than a mock-up). Extensive research has been done into possible materials for the sail, which must have “five-nines” (99.99999%) reflectivity and 0.000001% light absorption; the laser will fry it otherwise. Manchester explains that the final design will be a metamaterial – an artificial material formed from a solid base such as silicon or diamond, patterned with microscopic structures on its surface to manipulate the material’s response to the laser through constructive and destructive interference of incident light. While Klupar acknowledges that most current hardware and materials don’t meet the necessary specifications by “two or three orders of magnitude,” he and the rest of the team are confident that those discrepancies can be resolved relatively quickly. “Most people [on the team] believe we’re going to get this sail material developed within the next five years.” Manchester adds, “we can probably get a vehicle developed within the next five to ten years.”

Enlarge

breakthrough_starshot3
Concept art depicting the laser array, or "photon engine" as Klupar prefers to call it, that could power Starshot's massive 60,000 Watt laser.

Graphic by: Breakthrough Starshot

Both men acknowledge the bigger obstacle for Starshot is designing and building the laser array (Klupar prefers to call it a “photon engine”) which will accelerate the spacecraft within our solar system and send it off on its interstellar voyages. In order for the photon engine to function effectively, each individual laser in the array must share the same phase at a focal point 60,000 meters from Earth’s surface. Since lasers have wavelengths of only a few hundred nanometers, calibrating a kilometer-wide installation with hundreds of emitters is a near-impossible feat. There’s also the challenge of powering the array, which consumes the daily output of a mid-size power plant every two minutes. Still, the Starshot team is making progress. They’ve selected a site in a desert with a nearby natural gas pipeline that could be used to fuel a power plant. The site could also be enhanced with a solar farm as an alternative energy source. Research continues on methods to effectively converge the lasers.

Starshot is a long shot. It could be decades before the Starshot project fulfills its mission to visit Alpha Centauri. It is wholly possible that it will never reach that goal at all. That’s okay with Klupar and Manchester. “I think a decent return is motivating people to think about [sic] that they can actually go to the stars,” Klupar says – and that’s already happened. Prior to Starshot (and the fortune backing it), neither academia nor private companies believed that interstellar space travel would ever be realistic. Now, people are talking, scientists are experimenting, and visiting another star seems, at the very least, possible. 

Enlarge

breakthrough_starshot
Concept art depicts the laser-accelerated sail of Breakthrough Starshot as it heads from Earth towards the Alpha Centauri star system 4.367 light years away. Even accelerated by the laser to a speed 1/5th the speed of light, the journey would take over two decades and the enormous speed of the vessel as it approaches the star system would present its own set of challenges for imaging planets orbiting Proxima Centauri, the closest of the three stars in the system.

Graphic from presentation by Yuri Milner

That’s not to say that Klupar and Manchester believe that Starshot will fail – quite the opposite. Each conveys an almost obsessive, eager faith that the work of their team will ultimately result in success, revolutionizing spaceflight at the micro and macro level. The Breakthrough project isn’t just about sending miniature probes through the galaxy. It’s about moving humans – something else made all the more plausible by the physics of the photon engine. “The way the final speed scales for this thing is really interesting…it goes with the one-quarter power of the mass,” says Manchester. “ You have to go 16 times heavier to have your speed cut in half.” Humans may never be able to reach Alpha Centauri (and even at one-fifth the speed of light, it would take decades), but the same laser array used to propel Starshot’s nanocraft could move humans around the solar system in a matter of hours, facilitating intense exploration and possible colonization of our solar system. Starshot’s ultimate mission is to “build the highways” on which future vehicles will travel.

Nothing surrounding Starshot is normal. The proposed tech barely passes the sanity check. The amount of money behind it is obscene. Its parent organization, Breakthrough Initiatives, is led by Mark Zuckerberg and the Russian tech tycoon Yuri Milner (who’s provided most of the funding). It’s easy to scoff at the spectacle and spin surrounding the whole affair, not wholly unjustly. Manchester and Klupar are dedicated, intelligent scientists, but they’re also savvy hype-men.

If history illuminates the future, however, it speaks to the fact that difficult problems sometimes need unique, crazy-sounding solutions. Starshot may change space travel forever. It may also dissipate into the dust of history as an unsuccessful byproduct of engineering hubris. In the present, however, it should not be ignored. It should be encouraged; if not its methods, at least its spirit – a spirit of determination to discover the limits of humanity, coupled with relentless optimism.

About The Author

Alden Hunt