After a two-month trip to International Space Station, SpaceX and NASA are getting ready to complete their most important joint mission to date, crew Dragon Demo-2, which is the result of the partners' work on their Commercial Crew program designed to certify a SpaceX spacecraft for regular human spaceflight operations. NASA astronauts are already onboard Crew Dragon making their way back to Earth during a multi-hour descent, and later on, Sunday will be splashing down in the Atlantic Ocean off the coast of Florida.
Bob Behnken and Doug Hurley undocked from the International Space Station on Saturday, August 1 at just after 7:30 PM EDT, with the Crew Dragon capsule handling all of the maneuvers since in a fully automated fashion, just like it is designed to do.
SpaceX built Crew Dragon to be completely automated both during takeoff and the journey back to Earth and landing portion of any trip to the ISS, and in fact, have previously flown a successful uncrewed version of the mission that's happening now with astronauts on board.
A successful landing would signify that America once again has a fully serviceable, fully certified means of flying its own people into orbit and back.
This capability was lost when the country retired its shuttle.
Mission controllers are abiding by strict guidelines on permissible wind and wave conditions and will study the latest forecasts before giving "go" for re-entry.
After getting the go, Hurley's and Behnken's capsule will light its thrusters to begin the drop out of orbit.
It's a high-speed descent, initially at several kilometers per second, and will see Endeavour experience heating of up 2,000C on its shielded underside as it pushes down through the atmosphere.
Two sets of parachutes are programmed to deploy, a drogue system at about 5,500m (18,000ft) in altitude when the capsule is still moving at approximately 560km/h; and then hour main chutes, at 1,800m in height, which should gently deposit the vehicle on the ocean surface.
As is always the case with a re-entry, there will be a few minutes of radio silence as hot gases (plasma) temporarily envelop the craft.
It's 45 years since the last US crewed capsule made an ocean splashdown. That was an Apollo vehicle that returned to the Pacific after meeting up with a Soviet Soyuz craft above the Earth.