An unmanned capsule from Elon Musk's SpaceX has splashed down into the Atlantic Ocean after a short-term stay on the International Space Station, capping the first orbital test mission in NASA's quest to resume human space flight from US soil later this year.
After a six-day mission on the orbital outpost, Crew Dragon autonomously detached about 230am US eastern time on Friday and sped back to earth reaching hypersonic speeds before an 8.45am (0245 AEDT Saturday) splash-down in the Atlantic, about 320km off the Florida coast.
A SpaceX rocket launched the 5m-tall capsule from the Kennedy Space Center in Florida last Saturday.
Minutes before splash-down, Crew Dragon deployed its four parachutes, easing some concerns about functionality that both NASA and SpaceX had before the landing.
"Everything happened just perfectly, right on time the way that we expected it to," Benjamin Reed, SpaceX's director of crew mission management, said in a live stream from California.
SpaceX's Dragon capsule splashes down in the Atlantic. Source: AAP
The test mission was a crucial milestone in the US National Aeronautics and Space Administration's Commercial Crew Program ahead of SpaceX's first crewed test flight slated to launch in July with US astronauts Doug Hurley and Bob Behnken.
"This really is an American achievement that spans many generations of NASA administrators and over a decade of work by the NASA team," current administrator Jim Bridenstine said after the splash-down.
"The vehicle is doing well. The recovery crews are out. They're on the scene," said Steve Stich, the crew program's deputy manager with NASA.
A boat was in the zone where Dragon hit the Atlantic and was set to lift the spacecraft out of the water about one hour after splash-down using a crane. It will carry the craft back to land by Sunday.
The first-of-a-kind mission brought 180kg of test equipment to the space station, including a dummy named Ripley outfitted with sensors around its head, neck, and spine to monitor how a flight would feel for a human.
The space station's three-member crew greeted the capsule last Sunday, with US astronaut Anne McClain and Canadian astronaut David Saint-Jacques entering Crew Dragon's cabin to carry out air quality tests and inspections.
NASA has awarded SpaceX and Boeing Co a total of $US6.8 billion to build competing rocket and capsule systems to launch astronauts into orbit from American soil, something not possible since the US Space Shuttle was retired from service in 2011.
The launch systems are aimed at ending US reliance on Russian Soyuz rockets for $US80 million-per-seat rides to the $US100 billion orbital research laboratory, which flies about 400km above earth.
Bridenstine told Reuters the cost per seat on the Boeing or SpaceX systems would be lower than for the shuttle or Soyuz.
Privately owned SpaceX, also known as Space Exploration Technologies Corp, was founded in 2002 by Musk, who is also a co-founder of electric car maker Tesla.
