NASA Spacecraft

Because Omega was a NASA astronaut, that's why.

Space Plane

The in-universe replacement to the Space Shuttle. There were two versions: a low earth orbit, fully-reusable replacement for Shuttle, and an advanced version, being used to test more advanced propulsion systems. The hope was to eventually develop an interstellar drive, but after a nearly-disastrous accident that nearly destroyed the Kitty Hawk -- the mission on which Dr. Megan McAllister was to have flown, with disaster only averted by Alpha One's intervention -- the advanced space plane project was put on hold. NASA believed that the pilot of the space plane, Scott Chadwick, died in the accident, and this resulted in a re-evaluation of the project. In reality, Chadwick, who was close friends with McAllister, decided to leave NASA and join the Agency.

Space Shuttle (Space Transportation System, STS)

A partially-reusable low-Earth-orbit spaceplane. Crewed by 7. Operated from 1981-2011 by NASA, launched from KSC and initially landed at Edwards AFB, then landings were moved to the runway at KSC.

Four components:

There were a total of six named Shuttles.