SpaceX’s big new rocket has blasted off on its first test flight, carrying a red electric 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 lift-off, the Heavy became the most powerful rocket in use today, doubling the take-off punch of its closest competitor.
For the test flight, a red sports car made by another of Mr Musk’s companies, Tesla, was the unusual cargo, enclosed in protective covering for the launch.
The three boosters and 27 engines roared to life at Kennedy Space Centre 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.
Millions more watched online, making it the second biggest livestream in YouTube history.
Viewers were left with video images beamed from space of Mr Musk’s red Roadster circling the blue planet after the protective covering had dropped away and exposed the car.
A space-suited mannequin was at the wheel, named “Starman” after the David Bowie song.
“It’s kind of silly and fun, but I think that silly and fun things are important,” said the SpaceX chief who also runs Tesla and is keen to colonise Mars.
“The imagery of it is something that’s going to get people excited around the world.”
Two of the boosters — both recycled from previous launches — returned minutes after lift-off for on-the-mark touchdowns at Cape Canaveral. Sonic booms rumbled across the region with the vertical landings.
Musk later revealed the third booster, brand new, missed the floating landing platform and slammed into the Atlantic at 300mph, scattering shrapnel all over the deck and knocking out two engines.
He was unfazed by the lost booster and said watching the other two land upright was probably the most exciting thing he had ever seen.
Before lift-off, “I had this image of just a giant explosion on the pad, a wheel bouncing down the road, the Tesla logo landing somewhere,” he said. “But fortunately, that’s not what happened.”
Mr Musk’s rocketing Roadster is shooting for a solar orbit that will reach all the way to Mars.
Ballast for a rocket debut is usually concrete — “so boring”, he said in a post-launch news conference.
The Roadster was anything but. Cameras mounted on the car fed stunning video of “Starman” tooling around Earth, looking something like a racing driver out for a Sunday trip, with its right hand on the wheel and the left arm resting on the car’s door.
A sign on the dashboard read “Don’t panic!”, and Bowie’s Life on Mars? played in the background at one point. A Hot Wheels roadster was also on the dash with a tiny spaceman on board.
The Falcon Heavy is a combination of three Falcon 9s, the rocket that the company uses to ship supplies to the International Space Station and lift satellites.
SpaceX is reusing first-stage boosters to save on launch costs. Most other rocket makers discard their spent boosters in the ocean.