CAPE CANAVERAL, US (AP): A rocket ship built by Elon Musk's SpaceX company thundered away from Earth with two Americans on Saturday, ushering in a new era in commercial space travel and putting the United States back in the business of launching astronauts into orbit from US soil for the first time in nearly a decade.

NASA's Doug Hurley and Bob Behnken rode skyward aboard a sleek, white-and-black, bullet-shaped Dragon capsule on top of a Falcon 9 rocket, lifting off at 3.22 pm from the same launch pad used to send the Apollo astronauts to the moon a half-century ago. Minutes later, they safely slipped into orbit.

"Let's light this candle," Hurley said just before ignition, borrowing the words used by Alan Shepard on America's first human spaceflight, in 1961.

The two men are scheduled to arrive at the International Space Station on Sunday for a stay of up to four months, after which they will return to Earth in a Right Stuff-style splashdown at sea.

The mission unfolded amid the gloom of the coronavirus outbreak, which has killed over 100,000 Americans, and racial unrest across the US over the death of George Floyd, a handcuffed black man, at the hands of Minneapolis police.

NASA officials and others held out hope the flight would would be a morale-booster.

"Maybe there's an opportunity here for America to maybe pause and look up and see a bright, shining moment of hope at what the future looks like, that the United States of America can do extraordinary things even in difficult times," NASA Administrator Jim Bridenstine said before launch.

With the on-time liftoff, SpaceX, founded by Musk, the Tesla electric-car visionary, became the first private company to launch people into orbit, a feat achieved previously by only three governments: the US, Russia and China.

The flight also ended a nine-year launch drought for NASA, the longest such hiatus in its history. Ever since it retired the space shuttle in 2011, NASA has relied on Russian spaceships launched from Kazakhstan to take US astronauts to and from the space station.

In the intervening years, NASA outsourced the job of designing and building its next generation of spaceships to SpaceX and Boeing, awarding them USD 7 billion in contracts in a public-private partnership aimed at driving down costs and spurring innovation. Boeing's spaceship, the Starliner capsule, is not expected to fly astronauts until early 2021.

Musk said earlier in the week that the project is aimed at "reigniting the dream of space and getting people fired up about the future." Ultimately, NASA hopes to rely in part on its commercial partners as it works to send astronauts back to the moon in the next few years, and on to Mars in the 2030s.

Before setting out for the launch pad in a gull-wing Tesla SUV another Musk product Behnken pantomimed a hug of his 6-year-old son, Theo, and said: "Are you going to listen to Mommy and make her life easy?" Hurley blew kisses to his 10-year-old son and wife.

A launch attempt on Wednesday was called off with less than 17 minutes to go in the countdown because of lightning. On Saturday, stormy weather in Florida threatened another postponement for most of the day, but then the skies began to clear in the afternoon just in time.

Nine minutes after liftoff, the 260-foot rocket's first-stage booster landed, as designed, on a barge a few hundred miles off the Florida coast, to be reused on another flight.

"Thanks for the great ride to space," Hurley told SpaceX ground control. He and his crewmate batted around a sparkly purple toy, demonstrating that they had reached zero gravity.

Bridenstine pronounced it "just an amazing day." SpaceX controllers at Hawthorne, California, cheered and applauded wildly.

President Donald Trump and Vice President Mike Pence flew in for the launch attempt for the second time in four days.

"I'm so proud of the people at NASA, all the people that worked together, public and private. When you see a sight like that it's incredible," Trump said after liftoff.

Inside Kennedy Space Center, attendance was strictly limited because of the coronavirus, and the small crowd of a few thousand was a shadow of what it would have been without the threat of COVID-19. By NASA's count, over 3 million viewers tuned in online.

Despite NASA's insistence that the public stay safe by staying home, spectators gathered along beaches and roads hours in advance. Among them was Neil Wight, a machinist from Buffalo, New York, who staked out a view of the launch pad from a park in Titusville.

"It's pretty historically significant in my book, and a lot of other people's books. With everything that's going on in this country right now, it's important that we do things extraordinary in life," Wight said. "We've been bombarded with doom and gloom for the last six, eight weeks, whatever it is, and this is awesome. It brings a lot of people together."

Because of the coronavirus, the astronauts were kept in quasi-quarantine for more than two months before liftoff. The SpaceX technicians who helped them get into their spacesuits wore masks and gloves that made them look like black-clad ninjas. And at the launch centre, the SpaceX controllers were seated far apart.

Hurley, a 53-year-old retired Marine, and Behnken, 49, an Air Force colonel, are veterans of two space shuttle flights each. Hurley piloted the space shuttle on the last launch of astronauts from Kennedy, on July 8, 2011.

In keeping with Musk's penchant for futuristic flash, the astronauts wore angular white uniforms with black trim. Instead of the usual multitude of dials, knobs and switches, the Dragon capsule has three large touchscreens.