Multi-stage space rockets are a bittersweet affair: One minute, they're sitting on the launch pad, shiny, expensive, and awaiting an explosion-fueled climb. They next, they're dropping back to Earth in pieces, unceremoniously plopping in the ocean, and sent off to the scrap heap for good. Not anymore. In March, SpaceX launched a “used” Falcon 9 first stage, an unprecedented achievement in spaceflight. It was a milestone for the company, which designed the Falcon’s first stage to land upright—and intact—back on Earth after every launch. Perhaps more importantly, it proved SpaceX's concept valid. Rockets cost tens of millions or even hundreds of millions of dollars to build. Being able to reuse them could significantly reduce the cost of spaceflight. That may pave the way for all manner of aerospace innovations.
