If the Discovery contains an experimental spore drive, why doesn't it have a NX registry?

Question

In Star Trek Discovery S1:E3 Context is for Kings the protagonist Michael Burnham joins the USS Discovery. She finds that the ship has an experimental Spore Drive.

We know that The Federation used the NX prefix for experimental ships.

But the Discovery's ship number is NCC-1031.

Indeed, the following commentator writes:

Shouldn't the Discovery have an NX prefix, since it's an experimental vessel, with a spore drive?

My question is: If the Discovery contains an experimental spore drive, why doesn't it a NX registry?

Answer 1

The NX registry designation was used for experimental starship designs, basically a starship class prototype, not for ships that were used to test experimental technologies.

In other words, the NX meant that the whole new ship model was under test, not the single technologies that it carried on board; and the premise that the Discovery is an experimental ship, instead of a ship used for testing experimental technologies, is wrong and not supported by any evidence.

There is no indication that the USS Discovery was the first ship of its class and therefore considered to be a prototype (so being registered with a NX designation), as a matter of fact we have some clues that imply the contrary:

• we know that the USS Discovery registry number is NCC-1031, while its sister ship, the USS Glenn, had NCC-1030; this implies that the Glenn was launched before the Discovery; this eliminates every chance that that Discovery was the first of its class;
• we also know that both these vessels were Crossfield-class starships; there are many examples where the class name was also the name of the first ship of that class (Excelsior, Galaxy, Prometheus, Defiant); so we can safely assume that the first ship and prototype belonging to the Crossfield-class was the hypothetical USS Crossfield, that would have been the ship to be registered with a NX designation.

Answer 2

From your third link (USS Discovery):

Due to the outbreak of the Federation-Klingon War of 2256, a vessel as new as Discovery would normally have been pressed into service on the front lines, even though it would have a relatively small impact compared to other, more combat-oriented vessels. Instead, Discovery was placed under the command of Captain Lorca and given a clandestine mission to conduct black ops scientific research, developing top-secret weapons and technologies that would help the Federation win the war.

(Emphasis mine.) Using the NX prefix would have represented an unacceptable security risk.

Answer 3

Discovery is not an experimental starship in the sense that it was chosen first hand for development of the drive. The NX designation is used for the Lead ship; the first of it's type, then NCC follows it's sister ships (Crossfield, Glenn, Discovery) Examples USS Defiant: NX-74205, USS Prometheus: NX-74913