Here’s why plans for a ‘death laser’ in space have been put on hold

Plans to build a giant orbiting laser gun have been grounded indefinitely.

It sounds like the stuff of science fiction, but it’s real: Billionaire Yuri Milner seeks to send a handful of postage-stamp-sized space probes to a nearby star system, in an effort to prove that interstellar flight is possible. But as it turns out, the tricks we’d need to push those little spacecraft out of our solar system and into the heavens could have drastic unintended consequences.

Propelling those tiny probes requires hitting them with high-powered lasers. This laser isn’t just a souped-up version of your local planetarium laser show; some incarnations of the idea could become a supervillain’s doomsday machine, critics fear.

Milner, who made his fortune by investing in technology and social media, wants to send probes to Proxima Centauri b — an exoplanet orbiting the closest star to the sun, 25 trillion miles away. Known as Breakthrough Starshot, the initiative also paves the way for exploring nearby star systems for signs of life. It’s a companion project to Milner’s Breakthrough Listen, which seeks to detect extraterrestrial life by monitoring radio signals with huge satellite dishes stationed on Earth.

The science behind the project originates in the writing of physicist and science fiction author Robert Forward, a pioneer in the field of solar sails. Forward theorized that the tiny pressure from laser radiation could be used to drive lightweight sails, or tiny spacecraft, across interstellar distances. For Breakthrough Starshot, the laser array would shoot at a 1,000-some mini StarChip spacecraft, propelling them along their 20-year journey.

To avoid complications caused by Earth’s turbulent atmosphere, Forward originally advocated positioning the laser system in space, accompanied by a 100 gigawatt power station.

Yet there’s a constant tension in science between human ingenuity, which allows us to do extraordinary things, and the risk that humans can’t be trusted not to use their inventions to destroy things — intentionally or otherwise.

A miscalculation or technical failure in directing the laser could send those beams back to Earth, unleashing the equivalent destruction of several nuclear bombs. Such a device also could be sabotaged or seized by terrorists; it would certainly require round-the-clock security.

For these reasons, Breakthrough Starshot must overcome all kinds of red tape. The Outer Space Treaty, adopted by the United Nations in 1967, stipulates that the nation from which a spacecraft launches is “liable for the damage caused by their space objects,” even if the object is owned by a non-governmental organization.

Milner could circumvent this restriction by setting up shop in a rogue nation — one that is not party to the Outer Space Treaty. But this could be politically disastrous for his organization, as all major spacefaring nations have signed and ratified the treaty, and only a handful of non-signatories are located at the ideal latitude for launching spacecraft.

Milner himself wants to do something bold, but has expressed a reluctance to launch lasers into space. He told The Atlantic, “People who talk about lasers in space don’t think about policy issues, and they don’t think about cost.” He is opting for a ground-based laser because, he says, “Nobody will allow you to build something that you can point in all different directions, as you would be able to in space.”

But he’s also thinking hard about the danger of lasers in general: “This is a very big laser,” he admitted. “It can do quite a bit of damage.”

As with so much new technology, our abilities vastly outpace our understanding of potential consequences. Even Milner has questioned “whether we are a mature enough civilization to be doing this,” with a laser array of such power.

For that reason, there’s a fallback plan. For now, that 100 gigawatt-powered laser array will be earthbound. Possible locations in the Southern Hemisphere, where Proxima Centauri is more visible, include the Atacama Desert of Chile, one of the driest places on Earth, where a handful of international observatories have been stationed. Its remote location diminishes chances for disaster, or at least minimizes the number of people living nearby.

Meanwhile, Breakthrough Starshot has a few more technological kinks to work out. The data-return system, for example, hasn’t been perfected. Without new technology, the tiny spacecraft will fly past Proxima Centauri b armed with sensors, unable to send the information back to Earth.

And unless Milner finds international support and additional funding, there will be no laser at all. His $100 million pledge to Breakthrough Starshot is a fraction of the $5 billion to $10 billion price tag.

Jacob Haqq-Misra is a research scientist with the Blue Marble Space Institute of Science. Follow him on Twitter @haqqmisra