Forget the Starship Enterprise, the Battlestar Galactica, the Millennium Falcon and the Jupiter 2. In all likelihood, the first spacecraft to make the voyage from our solar system to neighboring stars won’t be big gleaming vessels under the command of heroic astronauts. This old-school space-opera scenario has inspired some great science fiction, but it ignores the fundamental challenge of interstellar travel: Even the stars closest to our sun—the three stars in the Alpha Centauri system—are more than 25trillion miles away. Without warp drive or wormholes to shorten the journey, it’s going to take a long, long time to get there.
On Tuesday, Russian billionaire and science-minded philanthropist Yuri Milner held a press conference in New York City to propose a more realistic strategy for interstellar travel, one that takes advantage of Isaac Newton’s second law of motion. You might remember this formula from high-school physics: force equals mass times acceleration. A spacecraft would need to accelerate to about twenty percent of the speed of light to travel to Alpha Centauri in twenty years. Propelling a typical NASA probe to such high speed is beyond the capabilities of any foreseeable technology. The spacecraft are simply too massive. But the task would be a lot easier if the craft could fit in the palm of your hand and was as light as a penny.
Over the past 15 years, rapid advances in microelectronics have made it possible to pack all the essential components of a spacecraft—radio, camera, power supply, and so on—into a chip that weighs less than a gram. (Milner calls it the StarChip.) Best of all, this tiny craft wouldn’t need to carry a bulky propulsion system or a heavy load of fuel; instead, it could be attached to an ultrathin lightsail and propelled by a powerful laser beam.
Under Milner’s plan, thousands of lasers arrayed at a site on the Earth’s surface would fire in precise synchrony so that their outputs can merge into a single beam shooting upward through the atmosphere with a power of 100 billion watts. The beam would focus on the lightsail of a StarChip previously launched into orbit. If the sail reflects the laser light instead of absorbing it, then the force delivered by all the colliding photons could swiftly accelerate the lightsail to twenty percent of light speed, propelling the spacecraft hundreds of thousands of miles in a mere two minutes. After that point, the craft would be so distant from the Earth that the laser beam could no longer push the craft, but the StarChip would already be cruising at 134 million miles per hour toward whatever star system the laser had targeted. And if the lightsails and StarChips can be manufactured cheaply enough, they could be launched into orbit by the hundreds, and the laser array could accelerate a new one toward the stars every day.
-More at Scientific American