The third long-duration astronaut team launched by SpaceX to the International Space Station (ISS) safely returned to Earth early on Friday, splashing down in the Gulf of Mexico off Florida to end months of orbital research ranging from space-grown chillies to robots.
The SpaceX Crew Dragon capsule dubbed Endurance, carrying three US NASA astronauts and a European Space Agency (ESA) crewmate from Germany, parachuted into calm seas in darkness at the conclusion of a 23-hour-plus autonomous flight home from the ISS.
Thermal-camera video of the splashdown, at about 12:45 a.m. EDT (0445 GMT), was carried live by a joint NASA-SpaceX webcast.
The Endurance crew, which began its stay in orbit on Nov. 11, consisted of American spaceflight veteran Tom Marshburn, 61, and three first-time astronauts: NASA's Raja Chari, 44, and Kayla Barron, 34, and their ESA colleague Matthias Maurer, 52.
Chari could be heard radioing thanks to mission control moments after splashdown.
In less than an hour, the heat-scorched Crew Dragon was hoisted onto a recovery ship before the capsule's side hatch was opened and the four astronauts were helped out one by one for their first breath of fresh air in nearly six months.
175 days in space
Still garbed in white-and-black spacesuits, their strength and equilibrium shaky from 175 days in a weightless environment, were assisted onto special gurneys as they waved and gave thumbs-up for cameras.
Each was to receive a routine medical checkup aboard the ship before being flown by helicopter back to Florida.
The return from orbit followed a fiery re-entry plunge through Earth's atmosphere, generating frictional heat that sent temperatures outside the capsule soaring to 1,930 degrees Celsius (3,500 degrees Fahrenheit).
Two sets of parachutes billowed open above the capsule in the final stage of descent, slowing its fall to about 24 kph (15 mph) before the craft hit the water off the coast of Tampa, Florida.
Applause from the SpaceX flight control centre in suburban Los Angeles was heard over the Webcast.
The newly returned astronauts were officially designated as NASA's "Commercial Crew 3," the third full-fledged, long-duration team of four that SpaceX has flown to the space station under contract for the US space agency.
SpaceX, founded in 2002 by Elon Musk, the billionaire CEO of electric carmaker Tesla Inc, who recently clinched a deal to buy Twitter, supplies the Falcon 9 rockets and Crew Dragon capsules now flying NASA astronauts to orbit from US soil.
The company also controls those flights and handles the splashdown recoveries, while NASA furnishes the crews and launch facilities at the Kennedy Space Center in Cape Canaveral, Florida, and manages US space station operations.
California-based SpaceX has launched seven human spaceflights in all over the past two years - five for NASA and two for private ventures - as well as dozens of cargo and satellite payload missions since 2012.
Crew 3 returned to Earth with some 250 kg (550 pounds) of cargo, including loads of ISS research samples.
Aside from carrying out routine maintenance while in orbit some 400 km (250 miles) above Earth, the astronauts contributed to hundreds of science experiments and technology demonstrations.
Highlights included studies of the genetic expression in cotton cells cultured in space, gaseous flame combustion in microgravity and the DNA sequences of bacteria inside the station.
Crew members also tested new robot devices, harvested chilli peppers grown in orbit and conducted experiments in space physics and materials science.
Barron and Chari performed a spacewalk to prepare the station for another in a series of new lightweight roll-out solar arrays, to be used eventually on the planned Gateway outpost that will orbit the moon.
Crew 3's return comes about a week after they welcomed their replacement team, Crew 4, aboard the space station. One of the three Russian cosmonauts also now inhabiting the station, Oleg Artemyev, assumed command of the ISS from Marshburn in a handover before Endurance departed early Thursday.