spaceSpace and Physics

A Startup Is Developing A 100-Gigawatt Laser To Propel A Probe To Another Star System. That May Be Powerful Enough To "Ignite An Entire City"

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Dave Mosher

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An illustration of a Breakthrough Starshot "nanocraft" being propelled toward the Alpha Centauri star system with a powerful laser beam. Breakthrough Foundation

  • Breakthrough Starshot wants to use powerful lasers to propel tiny robotic probes to Alpha Centauri, a nearby star system that may contain habitable planets.
  • Yuri Milner, a Russian-American billionaire, and other Silicon Valley investors are funding the project.
  • Starshot calls for a 100-gigawatt laser that could shoot into space and accelerate probes called StarChips to 20% of the speed of light.
  • Chief engineer Peter Klupar said the laser would be brighter than the sun and "could ignite an entire city" if reflected back to Earth.

An initiative called Breakthrough Starshot wants to explore another star system using ultra-powerful laser beams and wafer-thin spaceships.

It's a goal that sounds so fantastic, you'd be forgiven for dismissing it as science fiction. But it's no joke, and the project's chief engineer says millions of dollars' worth of work is moving along without any major snags.


Starshot's founders and collaborators include the late Stephen Hawking, Harvard University astronomer Avi Loeb, and Russian-American billionaire Yuri Milner. The concept is based on more than 80 scientific studies about interstellar travel.

Milner and other Silicon Valley investors have even paid $100 million to cover the first 10 years of research and development.

"They had us go and study a whole range of different approaches of how would we send an object to [another star]," Peter Klupar, the engineering director of the nonprofit Breakthrough Foundation and its Starshot initiative, told an audience at the Economist's Space Summit on November 1. "We ended up deciding that the only credible way to do it today was building a large laser based in probably Chile."

The project hopes to propel roughly 1,000 tiny "StarChip" spacecraft toward Alpha Centauri, the second-closest star system to Earth, at 20% of light-speed (about 134 million mph). Each "chip" would weigh 1 gram or less. Another destination under consideration is Proxima Centauri, which is even closer to Earth and may have a habitable planet.

A wide-field view of the sky around the bright star Alpha Centaur. ESO/Digitized Sky Survey 2 Acknowledgement: Davide De Marti

In either case, StarChips may start careening out of the solar system in the mid-2030s. Each one would accelerate to its insane cruising speed within minutes, thanks to the mighty laser blast beamed into space from Earth.

But Klupar noted that a 100-gigawatt laser "beamer" would be powerful enough to "ignite an entire city in minutes" if it were reflected off a mirror in space and back to Earth.

Vaporizing cities is not the goal of Starshot, of course.

Rather, if the plan works out, camera-wielding Starchips could send humanity the first close-up photos of Earth-size worlds by the 2060s. (The voyage would take about 25 years, then receiving data would take another 4-plus years depending on the destination.)


Starshot was unveiled in 2016, and Klupar said work on the project since then has moved right along.

An artist's depiction of a laser array that'd propel Starshot's "nanocraft" to nearby star. Breakthrough Prize

"You would think that this is all impossible, but we have folks at Caltech and the University of Southampton and Exeter University working on about 50 contracts on making all [of] this happen," Klupar said. "No one has come up with a deal-breaker that we can find yet. It all seems real."

Klupar and others are not deluding themselves about Starshot's many hurdles. Even the project's own studies regularly make room for dead ends.

Some of the internal research frets about the potentially untenable cost of building a laser facility. Other papers analyze the concept of a "light sail": the device that would need to "catch" the laser beam and convert its energy into motion.


Some researchers question whether such a sail would fall apart when faced with the heat or mind-numbing acceleration (about 60,000 times the force of gravity on Earth's surface). There's also a risk that the sail could steer a StarChip wildly off-course.

"The sail is very thin. It's about 400 atoms thick, it weighs about a half a gram, and it's four meters in diameter," Klupar said. "I think of it as 'reflective smoke.'"

There's also the pesky issue of gas and dust that lurk between stars; such material could blast a fast-moving spacecraft into robotic Swiss cheese.

Nevertheless, Starshot engineers and scientists either see ways around all these issues (such as accepting that a majority of spacecraft won't make it) or figure that future technological advancements could solve many of the problems within a couple of decades.

An edited photo of Starshot's "sprite" prototype spacecraft. Breakthrough Starshot

As an example of demonstrable progress, Klupar highlighted experimental 4-gram satellites, called "sprites," built and tested by Cornell. In June 2017, a fleet of six sprites rode into space aboard an Indian-built rocket.

"This first one was just a stunt just to see if it'd work," Klupar said. The launch was a success — the sprites used a temperature sensor and relayed the data to Earth along with a radio "beep" signal.

Such tiny spacecraft could be seen as a precursor to StarChips, Klupar said.

"It feels a lot like the way CubeSats felt 20 years ago," he said, referring to roughly fist- to breadbox-size spacecraft that are pervasive today.


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