The Enterprise series of Star Trek sees the flight and adventures of Earth's first warp 5 starship. This starship was the result of the "Warp Five program," which is referenced throughout the series (particularly since Captain Archer's own father was one of the main scientists involved in the program, along with Zefram Cochrane).
It seems to me that warp 5 must be a special warp factor of some kind, since a whole program was assembled specifically to achieve that speed and Earth's first deep space exploration mission wasn't initiated until warp 5 capabilities had been realized. I am wondering why warp 5 is such a special speed.
- Are there theoretical or engineering reasons why achieving warp 5 is particularly notable, as opposed to warp 4 or warp 6?
- Were speeds lower than warp 5 not practical/useful for a deep space mission of the type that Enterprise embarks on for the first two seasons?
- Was it a benchmark of achievement that other species used to evaluate the technological development of a civilization?