The Crew-1 mission is transporting NASA astronauts Mike Hopkins, Victor Glover and Shannon Walker and Japan Aerospace Exploration Agency astronaut Soichi Noguchi to the International Space Station aboard the Crew Dragon vehicle. That launch, in a capsule named Endeavour, was the first time that a crewed mission had lifted off from the United States to orbit since the retirement of NASA's space shuttles in 2011.
During their time at the space station, the crew members will conduct a range of scientific experiments, including growing radishes and using microgravity to test leukemia drugs.
An air leak caused an unexpected drop in capsule pressure less than two hours before launch, Nasa officials said.
Final reviews of the Crew-1 mission took place in late September.
To get to this point, SpaceX had to complete a number of milestones successfully, including a fully automated uncrewed ISS rendez-vous mission, and a demonstration of both a launch pad abort and post-launch abort emergency safety system for the protection of the crew.
It comes after the historic launch to the ISS in May of astronauts Bob Behnken and Doug Hurley aboard a SpaceX CrewDragon spacecraft.
Sunday's historic launch-the first of six planned NASA/SpaceX Commercial Crew Program flights-paves the way for a future of routine launches, ferrying global scientists to and from the ISS.
Following the rocket's launch into orbit, President Donald Trump responded to the news on Twitter.
Next year, the Embassy will announce another competition to attend Space Camp as part of our commitment to developing the youth and opening doors to new opportunities.
The mission is scheduled to lift off from Cape Canaveral in Florida at 11.27am today AEST.
Noguchi is a veteran with experience from two previous space missions, having been aboard the Space Shuttle Discovery in 2005 and a Russian Soyuz spacecraft for a 161-day stay on the ISS between 2009 and 2010.
In the intervening years, USA astronauts have had to hitch rides into orbit aboard Russia's Soyuz spacecraft.
The astronauts will live and work on the International Space Station for approximately six months, the longest human spaceflight in Nasa's history.
- Mr Victor Glover, 44, a Navy pilot from California, who will be taking his first flight to space.