Fault lies on both sides. In the early years, NASA failed to adequately fund the projects, the agency found in 2016. Later delays, however, have been technical. Boeing had trouble dealing with powerful launch vibrations, and SpaceX changed their capsule to land at sea rather than on land. The science of tossing a vehicle into orbit may be pretty straightforward, but actually designing and building a spacecraft that keeps astronauts safe is, it turns out, anything but. Now, even representatives from the rocket companies themselves aren't sure if they'll make the current 2019 deadline (neither company responded to requests for comment).