The U.S. space agency NASA has ordered a crewed mission to be launched by SpaceX to the International Space Station (ISS) sometime in late 2017. The order is the first for the Hawthorne, Calif.-based company founded by Elon Musk.

This is the second in a series of four guaranteed orders NASA will make under its Commercial Crew Transportation Capability (CCtCap) contracts. Boeing received its first crew mission order in May.

NASA's Commercial Crew Program (CCP) was formed to facilitate development of a U.S. commercial crew space transportation capability to and from the ISS. Since the retirement of the Space Shuttle program in 2011, the U.S. has had no ability to transport astronauts to the space station and has relied on Russia's Soyuz spacecraft for this purpose at an ever-increasing cost—almost $82 million per seat for the next two years, according to NASA.

According to NASA, commercial crew launches using SpaceX and Boeing will reduce the per-seat cost of transporting U.S. astronauts to the space station. However, the agency has warned Congress that if it does not receive the full requested funding for CCtCap contracts in fiscal year 2016 and beyond, it will delay the start of launches by U.S. companies.

SpaceX’s crew transportation system, including the Crew Dragon spacecraft and Falcon 9 rocket, has advanced through several development and certification phases. The company recently performed a design review demonstrating the transportation system which has reached a sufficient level of maturity to work toward fabrication, assembly, integration and test activities.

Kennedy Space Center undergoes modifications to adapt it to the needs of SpaceX's Falcon 9 and Falcon Heavy rockets. Image credit: SpaceX.Orders under the CCtCap 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 final flight approval. Each contract includes a minimum of two and a maximum of six missions.

A standard commercial crew mission to the station will carry up to four NASA or NASA-sponsored crew members and about 220 pounds of pressurized cargo. The spacecraft will remain at the station for up to 210 days, available as an emergency lifeboat during that time.

Deciding which of the companies—SpaceX or Boeing—will fly its mission to the station first will be made later.