Last weekend, the Delta II rocket—for 30 years a regular fixture on launchpads in the United States—lifted off for the final time. The vehicle, built by the United Launch Alliance, had long carried the title of the most reliable rocket in service. With a record 153 successful launches out of 155 flights, the 125-foot-tall monolith, with its sporty teal-and-white paint scheme, is now officially a figure of the past.