CAPE CANAVERAL, Fla.—SpaceX launched Christmas gifts, goodies, and supplies to the International Space Station on Tuesday and got a present in return: the company’s 100th successful rocket landing. The predawn liftoff from NASA’s Kennedy Space Center was barely visible in the fog and clouds, as the Falcon rocket hoisted a Dragon capsule loaded with more than 6,500 pounds (2,950 kilograms) of gear for the station’s seven astronauts. Several minutes later, the first-stage booster landed upright on an ocean platform, six years to the day that Elon Musk’s company accomplished its first booster touchdown in 2015. This particular booster was making its first flight. A few days ago, a SpaceX booster made its 11th flight. “It’s critical to lower the cost of spaceflight to continue to reuse these boosters more and more times. A hundred is a big milestone, so we’re excited about that,” said SpaceX’s Sarah Walker, a mission manager. …