The launch two months ago went about as smoothly as possible, flying American astronauts into orbit from US soil for the first time since 2011.
And SpaceX’s Dragon spacecraft docked so gracefully with the International Space Station that NASA astronauts Bob Behnken and Doug Hurley didn’t even feel it.
Now they are preparing to come home.
Even though Hurricane Isaias is projected to hit the east coast of Florida just as Dragon would be returning, NASA and SpaceX, which owns and operates the spacecraft, are still proceeding with a landing attempt, aiming for a site in the Gulf of Mexico off the Florida Panhandle, where the sea states and winds are expected to be amenable enough.
‘‘Not intuitive, but Isaias may actually help make nice weather on landing a few hundred miles west,’’ Zebulon Scoville, NASA’s flight director, wrote on Twitter Saturday morning.
If all goes well, the crew would undock from the station at about 7:34 p.m. Saturday and splashdown Sunday at 2:42 p.m.
Even without a menacing hurricane, the return journey is a treacherous one.
The spacecraft will have to withstand temperatures up to 3,500 degrees Fahrenheit as it plummets through the atmosphere.
A quartet of parachutes will have to slow the 21,200-pound capsule for a soft landing at sea. Then rescue crews will have to quickly recover the vehicle from the Atlantic Ocean or the Gulf of Mexico in what would be the first water landing for United States astronauts since a joint U.S-Soviet mission in 1975.
If all that weren’t challenging enough, NASA and SpaceX are attempting to bring the crew home in the midst of an unusually active hurricane season.
And the possibility of strong winds from Isaias kicking up an unruly churn has put NASA and SpaceX officials on alert.
But if SpaceX is able to bring Hurley and Behnken home safely in the first test flight with humans on board it would be the triumphant culmination of years of work and the opening of a new era in human spaceflight in which corporations play a starring role alongside NASA.
Last year, SpaceX successfully completed a test run of the mission without astronauts that went smoothly and paved the way for Hurley and Behnken’s mission.
Still, no one is ready to celebrate until they are safely home.
NASA and SpaceX have picked out seven different landing sites along the east and west coasts of Florida, ranging from approximately 22 nautical miles from shore to 175.
Two recovery ships will be ready to speed to the spacecraft once it lands.
NASA is also taking extra precautions to protect workers and the astronauts, including testing people who come in contact with the astronauts.
And everyone will be wearing masks.