United Launch Alliance, Boeing's joint company with Lockheed Martin, has started building the rocket in its facility in Decatur, Alabama. It will be used for the space taxi's first unmanned test meant to to prove the integrated system's design. It's extremely important to pass that test since it's part of NASA's certification process -- the agency needs to be sure Boeing's technology works before it puts astronauts in the Starliner.

While Boeing is busy working on Atlas V and the Starliner, SpaceX is also working on its own system. It showed off its Dragon 2 crew vehicle a couple of years ago, with its snazzy interior and large windows to give passengers a spectacular view of outer space. It's still also refining its Falcon Heavy rocket that will take the capsule to space, though we might see it blast off as soon as this November.