The 23-story tall Falcon Heavy, carrying a cherry red Tesla Roadster automobile into space as a mock payload, roared off its launch pad at 3:45 p.m. (2045 GMT) at the Kennedy Space Center in Cape Canaveral. It launched from the same site used by NASA's towering Saturn 5 rockets to carry Apollo missions to the moon more than 40 years ago.

The two side-boosters successfully separated from the center main-stage rocket and flew back to Earth for safe simultaneous touchdowns on twin launch pads at Cape Canaveral Air Force Station. The center booster was expected for a return landing on a drone ship floating at sea, but its fate was not immediately known.

The launch had been delayed for more than two hours due to wind-shear conditions.

The successful test launch marked a key turning point in Musk's privately owned Space Exploration Technologies, which stands to gain a new edge over the handful of rivals vying for lucrative contracts with NASA, satellite companies and the US military.

Going along for the ride in a bit of playful cross-promotional space theater was the sleek red, electric-powered sports car from the assembly line of Musk's other transportation enterprise, Tesla Inc.

The Tesla Roadster is supposed to be sent into a virtually indefinite solar orbit, on a path taking it as far from Earth as Mars. Adding to the whimsy, SpaceX has planted a space-suited mannequin in the driver's seat of the convertible.

Whether the car makes it onto its planned trajectory will not become clear for several more hours, SpaceX said.

Propelled by 27 rocket engines, the Falcon Heavy packs more than 5 million pounds of thrust at launch, roughly three times the force of the Falcon 9 booster that until now has been the workhorse of the SpaceX fleet.

The new heavy-lift rocket is essentially constructed from three Falcon 9s harnessed together side-by-side, and Musk has said that one of the most critical points of the flight would come as the two side boosters separate from the central rocket early in the flight. That occurred seemingly without a hitch.

If the demonstration flight succeeds, Falcon Heavy will rank as the world's most powerful existing rocket, with more lift capacity than any US space vehicle since the era of NASA's Saturn 5 rockets that took astronauts to the moon some 45 years ago.