As a species, we have made magnificent strides in robotic space exploration in the past decade. From exploring Pluto close-up for the first time to discovering our solar system is rife with underground liquid oceans, we now understand our little neighborhood of planets and moons better than ever before. It’s time to start talking about how we are going to explore the stars.
The Breakthrough Initiatives, created by Russian billionaire physicist Yuri Milner, is one of the most forward-thinking space exploration groups in the world. Among Breakthrough’s many ambitious projects is Breakthrough Starshot. The goal is to send hundreds of gram-sized spacecraft to the nearest star—Proxima Centauri, some 4.2 light-years away—and have them arrive within our lifetimes. The craft would then attempt to communicate with Earth and transmit photos of Proxima Centauri and its orbiting planet, Proxima b, back to us.
The Breakthrough Initiatives recently held an international conference called Breakthrough Discuss at Stanford University. Hundreds of researchers and engineers met to flesh out Breakthrough’s many ambitious space exploration goals. Starshot attracted perhaps the most interest due to its thrilling prospects and many technical challenges to overcome.
The verdict? “It looks feasible,” according to Harvard science professor Avi Loeb who chairs the advisory committee for Breakthrough Starshot.
Even though the target star system is closer to us than any other, it’s still mind-bogglingly far away: 25 trillion miles. Voyager 1, the spacecraft that has traveled farthest from Earth, has been flying at 38,000 mph for forty years, and it’s only a tiny fraction closer to Proxima Centauri than it was when it launched. At Voyager’s rate, it would take tens of thousands of years for the spacecraft to get anywhere close to Proxima Centauri, even if it were headed in the right direction.
Conventional rocket launches and gravity assist maneuvers just won’t take us anywhere near the stars. We need a new plan.
Laser Beams and Light Sails
Spaceflight generally evokes visions of giant rockets with fiery tails erupting off the pad at Cape Canaveral and flying out beyond the atmosphere. To maneuver to a destination after launch, spacecraft often use a liquid rocket fuel called hydrazine. This potent propellant, however, is much too heavy to launch in large quantities. It would be incredibly inefficient just to launch enough fuel to Mars for a return flight, let alone enough for an interstellar voyage. Fortunately, there’s a much more efficient way to zip around the stars, and it uses nothing more than energy from beams of electromagnetic radiation.
Light sails are reflective surfaces resembling tin foil that use photons from a source of light, such as a laser beam or the sun, to propel a spacecraft. When the photons of light bounce off the reflective surface, the energy is transferred to a small push, and the craft accelerates in the near-vacuum of space.