Commercial crew flights from Florida's Space Coast to the International Space Station will restore America's human spaceflight launch capability and increase the time US crews can dedicate to scientific research, which is helping prepare astronauts for deep space missions, including the Journey to Mars, Nasa said in a statement on Saturday.
This is the fourth and final guaranteed order Nasa will make under the Commercial Crew Transportation Capability (CCtCap) contracts.
Boeing received its two orders in May and December of 2015, and SpaceX received its first order in November 2015.
"The order of a second crew rotation mission from SpaceX, paired with the two ordered from Boeing will help ensure reliable access to the station on American spacecraft and rockets," said Kathy Lueders, Manager of Nasa 's Commercial Crew Programme.
"These systems will ensure reliable US crew rotation services to the station, and will serve as a lifeboat for the space station for up to seven months," Lueders noted.
SpaceX met the criteria for this latest award after it successfully completed interim developmental milestones and internal design reviews for its Crew Dragon spacecraft, Falcon 9 rocket and associated ground systems, Nasa said.
"We appreciate the trust Nasa has placed in SpaceX with the order of another crew mission and look forward to flying astronauts from American soil next year," Gwynne Shotwell, SpaceX President and Chief Operating Officer, said.
Orders under the Commercial Crew Transportation Capability contracts are made two to three years prior to actual mission dates in order to provide time for each company to manufacture and assemble the launch vehicle and spacecraft.
Each company also must successfully complete a certification process before Nasa will give the final approval for flight.