ELON Musk’s SpaceX Crew Dragon capsule has successfully docked with the International Space Station just 27 hours after it was launched.

It is expected to remain attached with the space station for five days before returning to Earth.

The capsule is due to splash down in the Atlantic Ocean in the morning on March 8.

The Falcon 9 rocket blasted off from NASA’s Kennedy Space Centre in Florida on time at 2.49am, local time, on Saturday.

The flight, which did not have a crew aboard, was a test to see if it possible to carry astronauts into space on a commercial spacecraft.

Musk, 47, admitted to being "emotionally exhausted" after his SpaceX Crew Dragon rocketship blasted off.

His company is working with NASA to resume sending US astronauts into space from American soil for the first time since 2011.

Speaking after the launch, Musk said the launch was "super stressful" to watch, but he's hopeful the capsule will be ready to carry people later this year.

He said: "To be frank, I'm a little emotionally exhausted.

"We have to dock to the station. We have to come back, but so far it's worked ... we've passed the riskiest items."

NASA Administrator Jim Bridenstine called it "a big night for the United States of America".

The only passenger was a life-size test dummy, named Ripley after the lead character in the Alien movies.

SpaceX needs to nail the debut of its crew Dragon capsule before putting people on board later this year.

This latest, flashiest Dragon is on a fast track to reach the space station Sunday morning, just 27 hours after lift-off.

It will spend five days docked to the orbiting outpost, before making a retro-style splashdown in the Atlantic next Friday all vital training for the next space demo, possibly this summer, when two astronauts strap in.

Bridenstine said: "This is critically important ... We're on the precipice of launching American astronauts on American rockets from American soil again for the first time since the retirement of the space shuttles in 2011.”

He got a special tour of the pad on the eve of launch, by SpaceX founder and chief executive Musk.

An estimated 5,000 people gathered in the wee hours at Kennedy Space Centre in Florida, as the Falcon 9 rocket blasted off from the same spot where Apollo moon rockets and space shuttles once soared.

Across the country at SpaceX Mission Control in Hawthorne, California, company employees went wild, cheering every step of the way until the capsule successfully reached orbit.

Looking on from Kennedy's Launch Control were the two NASA astronauts who will strap in as early as July for the second space demo, Doug Hurley and Bob Behnken.

It's been eight years since Hurley and three other astronauts flew the last space shuttle mission, and human launches from Florida ceased.

NASA turned to private companies, SpaceX and Boeing, and has provided them $8 billion to build and operate crew capsules to ferry astronauts to and from the space station.

Now Russian rockets are the only way to get astronauts to the 250-mile-high outpost. Soyuz tickets have skyrocketed over the years; NASA currently pays $82 million per seat.

Boeing aims to conduct the first test flight of its Starliner capsule in April, with astronauts on board possibly in August.

Bridenstine said he's confident that astronauts will soar on a Dragon or Starliner or both by year's end. But he stressed there's no rush.

"We are not in a space race," he said. "That race is over. We went to the moon and we won. It's done. Now we're in a position where we can take our time and make sure we get it right."

SpaceX already has made 16 trips to the space station using cargo Dragons. The white crew Dragon is slightly bigger 27 feet tip to tip and considerably fancier and safer.

It features four seats, three windows, touch-screen computer displays and life-support equipment, as well as eight abort engines to pull the capsule to safety in the event of a launch emergency.

Solar cells are mounted on the spacecraft for electrical power, as opposed to the protruding solar wings on cargo Dragons.