Elon Musk's SpaceX Crew Dragon rocket successfully launches from Florida on the way to the ISS. Credit: SpaceX.

Jitters aside by all the millions who watched on TV or on their computers, it could not have gone any better — the US is back in the business of human spaceflight.

The SpaceX Falcon 9 rocket and Dragon crew capsule carrying two NASA astronauts blasted off from the Kennedy Space Center in Florida exactly on schedule, while the rocket itself landed perfectly on a platform in the ocean, The Guardian reported.

The text-book launch marked the rebirth of the nation’s crewed spaceflight program as the first mission by a private contractor carrying humans into orbit. It was also the first launch of astronauts from US soil since the retirement of NASA’s troubled and expensive space shuttle fleet in 2011.

Astronauts Bob Behnken and Doug Hurley, both veterans of shuttle missions, will join their NASA colleague Chris Cassidy already aboard the International Space Station (ISS) in orbit 250 miles above Earth after docking on Sunday, The Guardian reported.

That journey will take approximately 19 hours, before they dock at the station.

“It’s absolutely our honor to be part of this huge effort to get the United States back in the launch business,” Hurley said from the flight deck moments before lift-off.

Today’s launch was attended by US President Donald Trump, whose administration has made space a policy priority.

“It’s incredible, the power, the technology,” said Trump. “That was a beautiful sight to see.”

This mission is the first crewed test flight for SpaceX, billionaire entrepreneur Elon Musk’s company, ahead of planned regular flights to the ISS commencing later this year, The Guardian reported.

Crew Dragon astronauts Bob Behnken and Doug Hurley, both veterans of shuttle missions, wave to onlookers before boarding the spaceship. Credit: SpaceX.

On Wednesday, the first launch attempt was called off just under 17 minutes before lift-off time when “surface electrical field” conditions near the launchpad made it too dangerous.

The main concern on Saturday appeared to be low clouds lingering over the space center. Even so, managers ordered the Falcon 9 rocket to be fuelled for flight, The Guardian reported.

The mission to the ISS will mark the first time since NASA’s space shuttle fleet was retired in 2011 that humans will be sent into orbit from the US.

Since then NASA has been reliant on the ageing Soviet-era Soyuz spacecraft launched by the Russian space agency from Kazakhstan, purchasing seats for up to US$85 million apiece, The Guardian reported.

NASA chief Jim Bridenstine has said resuming launches of American astronauts on American-made rockets from US soil is the space agency’s top priority, The Independent reported.

“I’m breathing a sigh of relief, but I will also tell you I’m not gonna celebrate until Bob and Doug are home safely,” Bridenstine said.

Musk, the South African-born high-tech entrepreneur who made his fortune in Silicon Valley, is also chief executive of electric carmaker and battery manufacturer Tesla, The Independent reported. He founded Hawthorne, California-based SpaceX, formally known as Space Exploration Technologies, in 2002.