Hurley said if he and Behnken got sick while bobbing in the waves awaiting recovery, it won't be the first time for a crew. Astronauts returning in the early 1970s from Skylab, Nasa's first space station, did not feel well following their splashdown, Hurley noted.
Feeling sick "is the way it is with a water landing," he said during the crew's final news conference from the International Space Station.
This will be SpaceX's first splashdown with astronauts on board, ending a two-month test flight that began May 30 at NASA's Kennedy Space Centre the first launch of a crew from the US in nearly a decade. The capsule has been docked at the space station since May 31, allowing Hurley and Behnken to chip in with spacewalks and experiments.
Hurley said the emergency and other equipment has checked out well aboard Dragon, dubbed Endeavour. Launch and rendezvous went flawlessly, "so we expect nothing different for the splashdown," he said.
Their departure leaves three on board, one American and two Russians. The Dragon capsule will be in the water for about an hour before it's hauled by crane onto a SpaceX recovery ship. It will be another hour before the hatch is opened and the astronauts emerge. Flight surgeons will be among the dozens of the recovery team members.
The plan is for the Dragon to undock from the space station on Saturday, a day before splashdown. The prime target is off the coast of Panama City, halfway between Tallahassee and Pensacola.
Falcon 9 lifts off from historic Launch Complex 39A and sends Crew Dragon to orbit on its first flight with NASA astronauts to the space station.
"We won't leave the space station without some good landing opportunities in front of us, good splashdown weather," Behnken told reporters. "We could stay up here longer. There's more chow and I know the space station program's got more work that we can do."
Like launch, the ride back will be essentially automated, with the crew and flight controllers intervening only if necessary.
Behnken has an extra reason to bring this Dragon back in good shape. Following refurbishment, the capsule will fly again next spring with a crew of four including his wife, NASA astronaut Megan McArthur. SpaceX's next astronaut flight is targeted for the end of September.
Behnken said even before his launch, they had an inkling she would be assigned to a SpaceX flight. NASA announced the news this week.
"And of course, I'll have a lot of tips for her," he said.
Hurley is married to recently retired NASA astronaut Karen Nyberg.
NASA turned to SpaceX and Boeing for US-based crew transport after the space shuttles retired in 2011. Russian rockets were the only way for astronauts to get to the space station until SpaceX became the first private company to launch humans into orbit two months ago. Boeing's first crew flight isn't expected until next year.
 "NASA")