SpaceX launched a Falcon Heavy rocket on Feb. 6 from the Apollo launchpad 39A at the Kennedy Space Center in Florida. (SpaceX)

KENNEDY SPACE CENTER, Fla. — SpaceX successfully launched what is now the world’s most powerful rocket Tuesday, a towering behemoth known as the Falcon Heavy that tore through the sky with the thundering force of 18 Boeing 747 jetliners.

Lifting off at 3:45 p.m. from the same launchpad that sent the crew of Apollo 11 to the moon, the rocket sent up a mountain-sized plume of smoke and a rattling roar across Florida’s Space Coast, where thousands gathered to watch. The mission represented the first test of the massive rocket, powered by 27 engines in three first-stage boosters that are essentially strapped together.

The maiden flight also marked the first time a privately financed venture ever attempted to launch a rocket so powerful that it was capable of hoisting a payload out of Earth's orbit. As a promotional stunt, SpaceX founder Elon Musk loaded the Falcon Heavy with his own cherry-red Tesla Roadster carrying a spacesuit-clad mannequin named "Starman" in the driver's seat. Musk said he planned to send the convertible, built by another one of his companies, into an orbit around the sun that would take it near Mars.

It was a beautiful day for a launch. Clear blue skies. A slight breeze. Warm weather that attracted space fans by the thousands who lined the beaches and causeways in anticipation. SpaceX topped off the launch by successfully landing two boosters on land, setting off twin sonic booms on their return. (A third first-stage, the so-called center core, crash landed at sea.) At SpaceX's headquarters, throngs of employees cheered wildly as the rocket soared out of the atmosphere.

"I’m still trying to absorb everything that happened because it seemed surreal to me," Musk told reporters later. "I had an image of a giant explosion on the pad with a wheel bouncing down the road and the Tesla logo landing somewhere. But fortunately that’s not what happened. The mission seemed to have gone as well as possible."

If SpaceX can fly the Falcon Heavy reliably, the rocket could prove useful to the Pentagon for lifting national security satellites and to NASA for helping its human exploration goals. SpaceX says the rocket is capable of hauling more mass farther than any existing rocket — an estimated 140,000 pounds to low Earth orbit, and nearly 40,000 pounds to Mars.

But industry officials say there are some concerns about how big the market is for the Falcon Heavy. SpaceX had been planning to fly a pair of tourists around the moon as early as this year. But on Monday, Musk announced a reversal, saying the Falcon Heavy probably would never fly humans, as the company shifts its focus to its next-generation rocket, known as the “BFR,” or “Big Falcon Rocket.”

Still, the Falcon Heavy’s successful launch represents a “revival of the exploring spirit,” said John Logsdon, a space historian who is a professor emeritus at George Washington University.

NASA's space shuttle program, which ended in 2011, was limited to what’s known as low Earth orbit, where the International Space Station flies at about 250 miles above the surface of the earth.

But the Falcon Heavy represents a chance to go beyond that, into deep space, to really “push the frontier,” Logsdon said. “This really gives us a capability that this country has not had since the last Saturn V flight, which was in 1973.”

SpaceX founder Elon Musk launched a Tesla sports car into space on Feb. 6, along with a "driver" dubbed Starman. The car will eventually be put in orbit around the sun. (SpaceX)

SpaceX’s launch comes as the Trump administration is focused on returning to the moon. While it has not released details of its plans or their cost, officials support having NASA partner with commercial companies such as SpaceX, which are striving to make space travel far more affordable than it has been in the past.

“It’s hard for me to overstate the importance of the launch today,” said Lori Garver, a former NASA deputy administrator. “I think this could end up being really the savior of NASA and deep space exploration.”

Commerce Secretary Wilbur Ross, a member of the reconstituted National Space Council, was on hand Tuesday to view the launch. In an interview, he lauded SpaceX’s efforts in bring back to the United States a large portion of the world market share for launches. And he said that one of the council’s top priorities is “how to accelerate the progress of the commercialization of space. We’re moving quite aggressively to try to accomplish that.”

SpaceX’s successful launch raises questions for NASA about how best to proceed. For years, the space agency has been working to develop the Space Launch System, an even more powerful rocket than the Falcon Heavy, but at about $1 billion per launch, it is many times more expensive. Ross said there is room for both systems.

“Space is a big, big thing,” he said.

After the launch, SpaceX broadcast a live stream from the Roadster in space using the three cameras mounted to the vehicle. In addition to carrying a plaque with the names of 6,000 SpaceX employees, the car also transported a data storage device containing Isasac Asimov’s classic Foundation science fiction trilogy.

Aaron Gregg in Washington contributed to this report.

An earlier headline suggested the Tesla would be going to Mars. The plan is to put the vehicle in an orbit that will take it near the planet. The post has been updated.