Elon Musk's commercial space service company, SpaceX is an established partner of NASA when it comes to transporting cargo to the International Space Station (ISS) using its Falcon 9 and Dragon spacecraft. Along with Boeing, SpaceX will also transport astronauts to space.

This time, NASA ordered another mission from SpaceX to transport crew of astronauts to the ISS. This is within the Commercial Crew Transportation Capability (CCtCap) contract by NASA. Aside from SpaceX, Boeing is also part of the agreement.

SpaceX is building the Crew Dragon while Boeing is also developing its CST-100 Starliner both scheduled to debut this in the next one year or two. NASA announced earlier that there will be commercial space shuttles that will transport crew from Earth to the ISS.

"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," Kathy Lueders, manager of NASA's Commercial Crew Program, said in a statement published by Space Flight Insider. "These systems will ensure reliable U.S. crew rotation services to the station, and will serve as a lifeboat for the space station for up to seven months," Lueders added.

The contracts within CCtCap are made more than two years before the mission launch to give commercial space companies ample time to build, manufacture and even test their capsules. The capsules have to pass NASA certification before it will be allowed for flight.

In preparation for this commercial space capsules docking with the ISS, SpaceX earlier delivered the new type of docking port into the space station that will be used for the new commercial crew program. This is because the capsules being developed by SpaceX and Boeing are different from the Russian's Soyuz capsule that is currently being used to transport crew in and out of the Earth.

SpaceX's Crew Dragon is similar to the Dragon cargo spacecraft that delivers good to the ISS. But the Crew Dragon is fitted with life support and control systems, it is also capable of transporting up to seven crew at a time, according to the Verge.

Boeing already said that their launch will be in 2018 but it looks like SpaceX can potentially launch by 2017 depending on NASA's certification approval.