The quartet of newly minted citizen astronauts comprising the SpaceX Inspiration4 mission safely splashed down in the Atlantic off Florida's coast on Saturday (Sept 18), completing a three-day flight of the first all-civilian crew ever launched into Earth orbit.

SpaceX's Crew Dragon capsule, dubbed Resilience, parachuted into the sea around 7pm EDT (7am on Sunday, Singapore time), shortly before sunset, after an automated re-entry descent, SpaceX said during a live webcast shown on its YouTube channel.

Within an hour, the four smiling crew members were seen emerging one by one from the capsule's side hatch after the vehicle, visibly scorched on its exterior, was hoisted from the ocean to the deck of a SpaceX recovery vessel.

Each of the four stood on the deck for a few moments in front of the capsule to wave and give thumbs-up to the cameras.

Each was then escorted to a medical station onboard for checkups they were to undergo at sea.

Afterward, the amateur astronauts were to be flown by helicopter back to Cape Canaveral for reunions with loved ones, SpaceX said.

The return from orbit followed a plunge through Earth's atmosphere generating frictional heat that sent temperatures surrounding the outside of the capsule soaring to 3,500 deg F (1,927 deg C). The astronauts' flight suits are designed to keep them cool if the cabin heats up.

Applause was heard from the SpaceX flight control centre in suburban Los Angeles as the first parachutes were seen deploying, slowing the capsule's descent to about 24kmh before splashdown, and again as the craft hit the water.

The astronauts were cheered again as they stepped onto the deck of the recovery ship.

First out was Hayely Arceneaux, 29, a physician assistant at St. Jude Children's Research Center in Tennessee, a childhood bone cancer survivor herself who became the youngest person ever reach Earth orbit on the Inspiration4 mission.

She was followed in rapid succession by geoscientist and former NASA astronaut candidate Sian Proctor, 51, aerospace data engineer and Air Force veteran Chris Sembroski, 42, and finally the crew's billionaire benefactor and "mission commander" Jared Isaacman, 38.

SpaceX supplied the spacecraft, launched it from Florida and flew it from the company's suburban Los Angeles headquarters.