NASA said the spacecraft returned to Earth with more than 3,800 pounds (more than 1,700 kilograms) of cargo, including specimens from biological experiments conducted on-board the space station.
"We're flying American astronauts on American rockets from American soil", NASA administrator Jim Bridenstine said during the presentation ceremony at the Johnson Space Center of Houston.
Since the space shuttle program was shut down, the USA space agency NASA has had to rely on Russian Federation to fly astronauts to space station, a $100 billion orbital research laboratory that flies about 250 miles (402 km) above Earth.
Their voyages are scheduled to begin next year, and they would be the first American astronauts to launch from US soil since 2011.
On the SpaceX vessel will be astronauts Doug Hurley, Victor Glover, Robert Behnken and Michael Hopkins.
The astronauts named on Friday will be carried aloft aboard spacecraft developed by entrepreneur Elon Musk's SpaceX and Boeing Co, crewing first the test flights, and then missions involving both Boeing's CST-100 Starliner and SpaceX's Crew Dragon. At nearly 240 feet long, more than 350 feet wide, nearly 70 feet tall and weighing in at around 925,335 pounds; a fair portion of the giant structure will likely survive re-entry and reach the Earth's surface like a fiery meteorite (between 53,500 and 173,250 pounds worth by NASA's estimate).
Josh Cassada, 45, will fly with Sunita ("Suni") Williams, 52, aboard Nasa's first contracted Starliner mission. She has logged 322 days in space.
Both vehicles will launch from Florida - Boeing's Starliner, boosted by a United Launch Alliance Atlas V rockets, from Cape Canaveral Air Force Station and SpaceX's Dragon from pad 39A at Kennedy Space Center. SpaceX is targeting November for its inaugural Crew Dragon test flight, but Boeing won't launch its passenger spacecraft Starliner until late this year or early next. "It will be thrilling to see our astronauts lift off from American soil, and we can't wait to see them aboard the International Space Station". They were two of the four astronauts selected by NASA in July 2015 to be trained to fly commercial crew missions. They're both the result of NASA's Commercial Crew Program: a almost 10-year-long, $8-billion effort to maintain access to orbit for USA astronauts.
The crew assignments came a day after NASA issued new schedules for the uncrewed and crewed test flights, pushing back the flights by several months from earlier schedules. He will be joined by Victor Glover, a Navy commander who will be making his first trip into space. Hopkins was a member of Expedition 37 and 38 in 2013 and 2014.
NASA TV is broadcasting video of the announcement live from Texas. The crew includes shuttle astronauts, crew members from the International Space Station and even some who have never flown out to space.
The new spaceflight capability provided by Boeing and SpaceX will allow NASA to maintain a crew of seven astronauts on the space station, thereby maximizing scientific research that leads to breakthroughs and also aids in understanding and mitigating the challenges of long-duration spaceflight. The launch window for the mission opens at 3:48 a.m EDT on August 11, 2018.