NASA has tapped Boeing’s CST-100 and SpaceX’s Falcon9/Crew Dragon spacecraft for transporting crews to the International Space Station (ISS) from 2017.

Boeing will receive a fixed price contract of $4.2 billion and SpaceX $2.6 billion, which will cover a test programme that includes a single crewed flight test per company with at least one astronaut aboard, says NASA. The missions will be used to verify the modules’ ability to launch, manoeuvre in orbit, and dock with the ISS.

“These Commercial Crew Transportation Capability (CCtCap) contracts are designed to complete the NASA certification for human space transportation systems capable of carrying people into orbit,” says NASA.

“Once certification is complete, NASA plans to use these systems to ferry astronauts to the International Space Station and return them safely to Earth.”

Following the retirement of the Space Shuttle in 2011, the US has been dependent on Russia for sending astronauts into space.

Boeing’s CST-100 is designed to carry up to seven passengers or a mix of crew and cargo to the ISS or low earth orbit.

Under CCtCap Boeing will build three CST-100s at Florida’s Kennedy Space Centre. In 2016 the spacecraft will conduct a pad-abort test, followed by an unmanned flight in early 2017. In mid-2017 the CST-100 will conduct a manned mission to the ISS.

SpaceX’s winning bid, which comprises the Falcon 9 launch vehicle and Crew Dragon spacecraft, is also capable of carrying seven astronauts.

SpaceX has a $1.6 billion deal from NASA to operate resupply missions to the ISS using its Dragon unmanned spacecraft.

Both systems are designed to be reusable. Videos on the web sites of the two contractors show that Crew Dragon will use rocket boosters for precision landings, while the CST-100 will use conventional parachutes.

NASA says that by outsourcing the low earth orbit mission to private industry, it will be able to focus on sending humans to Mars.