The Delta II rocket came, it saw, and for a time it conquered

United Launch Alliance

On Saturday morning, the most successful rocket the United States has ever developed flew its final mission. During the pre-dawn hours, United Launch Alliance's Delta II rocket lifted NASA's ice-monitoring mission ICESat-2 into space. It was a bittersweet moment, as the Delta II's retirement marks both a step into the future of US rocketry, while representing a definitive break with the past—and the very origins of US spaceflight.

"Historic day," the chief executive officer of United Launch Alliance, Tory Bruno, said on Twitter. "Retired the shark, Delta II and the mighty Thor." The "shark" was a reference to the shark teeth painted on the payload fairing of GPS launches, an homage to the "Flying Tigers," American volunteer pilots who helped defend China from Japan in 1941 and 1942.