American physicist and science-fiction writer Robert Forward took the lead in the 1970s, further developing the lightsail concept. By 1984, Forward’s work led him to publish a paper in the Journal of Spacecraft and Rockets titled “Roundtrip Interstellar Travel Using Laser-Pushed Lightsails.” In it, he outlined how the laws of physics did not forbid using lightsails to venture to other stars. However, Forward also noted that “whether it can be engineered and is financially or politically feasible is left for future generations to determine.”
Despite the daunting, multipronged challenge of interstellar travel, in 1985, Forward created actual plans for an ultra-light interstellar probe powered by microwave lasers, or masers. He called it Starwisp and, in the 1990s, NASA Glenn Research Center scientist Geoffrey Landis jumped into the fray to elaborate on Forward’s basic design. But Starwisp never took flight. In 2005, the Planetary Society launched its own solar sail, Cosmos-1, but it failed to reach orbit.
Finally, in 2010, nearly a century after the notion of sailing on sunlight was first outlined in detail, the Japan Aerospace Exploration Agency (JAXA) successfully launched a solar sail named Interplanetary Kite-craft Accelerated by Radiation of the Sun (IKAROS), which hitched a ride to Venus with the climate orbiter Akatsuki. Once in position, IKAROS cleverly spun at some 25 revolutions per minute to unfurl its 46-foot-wide (14 m) sail, which was just 0.0003 inch (7.5 micrometers) thick — or about one-third the width of a human hair. Within a month, JAXA reported photons from the Sun were indeed accelerating IKAROS as planned, boosting its speed by a relatively modest 890 mph (1,430 km/h). And by utilizing adjustable LCD panels embedded near the edges of its sail, the spacecraft was even able to adjust the force pushing against it, changing its orientation at will.
With the technology behind lightsails finally proven to work in space, Russian billionaire Yuri Milner picked up the ball a few years later. In May 2015, Loeb says, Milner nonchalantly asked him to look into the idea of interstellar spacecraft that could sail on light. The task took the eternally inquisitive Loeb and his team some six months to exhaustively research.
By early 2016, Milner was convinced an interstellar mission was feasible — or at least soon would be if technology continued to sprint forward. He officially kicked off the Breakthrough Starshot project by contributing $100 million of his own money to fund proof-of-concept research and development not just for lightsails, but also for the other advanced technology required to send a craft to another star within a generation. Ever since, dedicated scientists and engineers have been tirelessly working to make this ambitious dream a reality, taking advantage of additional funding from multiple NASA grants.
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