(covers information from several alternate timelines)
NX-Alpha was one of three test vehicles, along with the NX-Beta and the NX-Delta, used in Starfleet's NX Project, the effort to test and refine the warp five engine designed by Henry Archer. As such, it was a predecessor of the NX-class starship.
Several commanders in Starfleet competed to be chosen as the first to fly NX-Alpha in the effort to break the warp 2 barrier. After several weeks, it became clear the competition was down to Jonathan Archer, Henry Archer's son, and A.G. Robinson. Although Archer had logged more flight hours in the simulator, Commodore Forrest selected Commander Robinson.
In 2143, Commander Robinson flew NX-Alpha while Commander Archer monitored from Starfleet Command. Initially, there was an imbalance in the power systems, causing them to keep NX-Alpha in orbit. When they finally gave him the okay, Robinson jumped to warp 1.
The ship successfully attained warp 2, but the power systems began rapidly overloading. Command ordered him to drop to sublight, but Robinson believed it could be pushed a little further. After attaining warp 2.2, NX-Alpha broke up just outside of orbit of Jupiter. Luckily, Robinson was able to eject in an escape pod that was retrieved and brought back to Earth.
Afterward, the Vulcan Advisory Council insisted on pausing the program until the Human scientists could figure out what had gone wrong, and run more simulations. Robinson told the inquiry that it was a design flaw in the engine, although Commander Archer and Lieutenant Charles Tucker asserted that it was actually pilot error. The results of NX-Alpha's mission eventually led to the unapproved flight of the NX-Beta. (ENT: "First Flight")
|NX prototypes: NX-Alpha • NX-Beta • NX-Delta|
|Commissioned ships: Enterprise NX-01 • Columbia NX-02 • NX-03 • NX-04|
|Mirror universe: ISS Enterprise NX-01 • ISS Avenger NX-09|