SpaceX chief Elon Musk says the centre booster of the Falcon Heavy slammed into the Atlantic at 480km/h, missing the floating landing platform.
Musk says it hit the water with such force that shrapnel flew onto the droneship's deck and took out two engines.
Despite the loss, Musk reveled in Tuesday's successful launch of the powerful Falcon Heavy and the recovery of the two side boosters.
He said watching the simultaneous side-by-side touchdowns of those two boosters at Cape Canaveral Air Force Station was probably the most exciting thing he's ever seen.
If the cameras on the ocean platform were not wiped out, Musk says he'll try to salvage the video and add the images to his greatest bloopers' reel of exploding rockets.
The Falcon Heavy rocket blasted off Tuesday afternoon from the same Florida launch pad used by NASA nearly 50 years ago to send men to the moon. With liftoff, the Heavy became the most powerful rocket in use today. Its three boosters and 27 engines roared to life at Kennedy Space Center.
Not only did the rocket lift a red sports car into orbit — with a dummy "Starman" at the wheel — two of the three boosters came back and landed upright at Cape Canaveral. The 15-story boosters landed at the same time, side by side.
Musk owns the rocketing Tesla Roadster, which is aiming for a solar orbit reaching Mars.
Musk — who also heads up the Tesla electric carmaker — says he wanted to add some dramatic flair. Usually there are things like steel or concrete slabs or mundane experiments on test flights. SpaceX is targeting a long, oval orbit around the sun for the car.