History-making NASA-SpaceX astronauts undock from International Space Station, set for splashdown

Two months after a history-making launch, the first NASA-SpaceX astronauts have undocked from the space station and are set for splashdown on Sunday.

Doug Hurley and Bob Behnken, who left Earth on May 30, undocked from the International Space Station at about 7:30 p.m. ET on Saturday and will splash down off the coast of Florida at 2:48 p.m. ET on Sunday. Their journey will be broadcast live by NASA.

Although weather was a top concern as Hurricane Isaias heads to Florida, NASA’s forecasters were encouraged enough to press ahead with undocking.

Stakes are high as the astronauts only have 48 hours of oxygen in their capsule now that the Crew Dragon spacecraft has undocked from the ISS.

Behnken said a day prior to the undocking he wasn't concerned about a possible delay.

"I still don't feel nervous about it -- we're focused on the things we need to do to be as safe as possible," Behnken said about the weather. "We won't leave the space station without good landing opportunities in front of us. We don't control the weather, we know we can stay up here longer, there's more chow."

Their return would mark the first time a commercially built American spacecraft returned from space. It's also NASA's first crewed water landing since 1975.

Hurley said every spaceflight is a "once-in-a-lifetime experience" for astronauts, but "this one probably is a great topper, at least for me, personally."

"The water-landing portion of it is pretty challenging from a physiological standpoint," he noted, especially after being in a microgravity environment for months. He said they have exercised "very hard" to help prepare.

In addition, Hurley said if they get physically ill during their return they will have the "appropriate hardware."

"Just like an airliner, there are bags if you need them, and we'll have those ready," he added. "If that needs to happen, it certainly wouldn't be the first time it's happened in a space vehicle."

Splashdown expectations

There are seven possible splashdown sites near coastal cities -- Pensacola, Tampa, Tallahassee, Panama City, Cape Canaveral, Daytona and Jacksonville -- and NASA said it will make a final selection based on several factors, primarily weather. As of Saturday, near Pensacola was considered the primary site.

Once the spacecraft enters Earth's atmosphere, it will deploy two sets of parachutes at about 18,000 feet in altitude and then four more at about 6,000 feet in altitude, according to NASA.

After the splashdown, SpaceX will send two boats to first check the capsule and make sure the area around it is free of hypergolic propellant vapors. The second boat will recover the parachutes.

The first boat then will hoist the capsule with Hurley and Behnken in it and move it to a stable location for the hatch to be opened as medical professionals look on. After a medical check, Behnken and Hurley will board a NASA plane to Houston.

Behnken said Friday he is most excited to see his family and his 6-year-old son upon returning to Earth, saying, "He's changed a lot in the couple of months that we've been up here."

Behnken added that he already has some tips for his wife, fellow astronaut Megan McArthur, who will be on a NASA-SpaceX mission scheduled to launch next spring.

"A lot of them will be about how life on the space station goes," he said. "I'll definitely have some advice about living inside of Dragon and where best to pack all your personal items so you can get to them conveniently."