CAPE CANAVERAL, Florida - SpaceX's big new rocket blasted off Tuesday on its first test flight, carrying a red sports car aiming for an endless road trip past Mars.

The Falcon Heavy rose from the same 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, doubling the liftoff punch of its closest competitor.

The three boosters and 27 engines roared to life at Kennedy Space Center, as thousands watched from surrounding beaches, bridges and roads, jamming the highways in scenes unmatched since NASA's last space shuttle flight. At SpaceX Mission Control in Southern California, employees screamed, whistled and raised pumped fists into the air as the launch commentators called off each milestone.

Two of the boosters - both recycled from previous launches - returned minutes later for simultaneous, side-by-side touchdowns on land at Cape Canaveral. Sonic booms rumbled across the region with the vertical landings. There was no immediate word on whether the third booster, brand new, made it onto an ocean platform 300 miles offshore.

SpaceX Chief Executive Elon Musk owns the rocketing Tesla Roadster, which is shooting for a solar orbit that will reach all the way to Mars. As head of the electric carmaker Tesla, he combined his passions to add a dramatic flair to the Heavy's long-awaited inaugural flight. Ballast for a rocket debut is usually concrete or steel slabs, or experiments.

Cameras mounted on the car fed stunning video of the convertible floating high above the ocean with its driver, a space-suited dummy, named "Starman" after the Davie Bowie song. A sign on the dashboard read: "Don't panic!" Bowie's Life on Mars? played in the background at one point.

"View from SpaceX Launch Control," Musk wrote via Twitter. "Apparently, there is a car in orbit around Earth."

Minutes later, he provided a livestream of "Starman" tooling around the blue home planet, looking something like a NASCAR racer out for a Sunday drive, with its right hand on the wheel and the left arm resting on the car's door.

On the eve of the flight, Musk told reporters the company had done all it could to maximize success and he was at peace with whatever happens: success, "one big boom" or some other calamity.

ASSOCIATED PRESS