The Prototype (Y) status prefix indicates that the aircraft in question is a test property under active development as part of a military development program, and is at least theoretically intended to go into mass production it the design meets the military's requirements. Sometimes, prototype designations are used to camouflage a program's actual intentions in order to keep certain details out of the public record at the time. For instance, the USAF has used incorrect prototype designations to conceal the existence of derivative programs... the SR-71 the USAF gave to NASA for testing was given the designation YF-12C to conceal the existence of the SR-71 program. In-universe, the YF-30 Chronos was given a prototype designation instead of an experimental designation so that its developer could avoid disclosing the specifications of the proprietary system it was actually an experimental technology demonstrator for... the Fold Dimensional Resonance system.
It depends on the program, really.
Very rarely, there will be an undesignated early proof-of-concept that will be known only by a codename... such as the Lockheed Have Blue (AKA the "Hopeless Diamond") that was an early proof of concept for another program that was codenamed Senior Trend (the YF-117) that was developed into the F-117A Nighthawk. Have Blue would likely have been classified as an Experimental plane if it hadn't been so damned secret.
The normal trajectory in Macross is to start with an Experimental (X) airframe to prove out the concept, then a Prototype (Y), then the final aircraft.
Because the designation system is based on the intended use of a design and its level of development, I don't think there is really any case of the military assigning an incorrect designation by accident. There are cases where they have done so deliberately either to indicate a design was put into production without approval (e.g. the VF-27 the NUNS considers to be YF-27 and YF-29B) or to conceal the existence of a program (e.g. the YF-12C/SR-71).
The problems experienced by the F-117, B-2, F-22, and F-35 are because those aircraft are passively stealthy and derive their stealth from a combination of the shape of their airframes, special composite materials used in their airframes that absorb or at least do not reflect radio waves, and a special paint that contains iron particles which absorb radar waves and convert their energy into heat. The issue with the aforementioned aircraft is in the iron-based paint, which doesn't hold up well in humid environments because of the binders used to hold the iron in its structure and keep it adhered to the composite airframe.False Prophet wrote: ↑Fri May 22, 2020 7:56 amSay, how hard is it to maintain VF with stealth capability like the VF-17? I recently read some articles from the 1990s complaining about how much money went to maintaining the F-117 and the B-2 (like storing them in environment-controlled rooms), both of which becoming basically paperweights.
Macross's VFs don't really have that problem. Most of them primarily rely upon active stealth technology to conceal themselves from detection. That's a system that analyzes incoming radar waves and produces a wave of equivalent frequency and amplitude but with an opposite phase. This effectively cancels out the radar wave by making the net amplitude of the combined radar wave 0, so the enemy radar sees that space as empty despite it actually getting returning radar waves. This method is called active cancellation, and it's also commonly used in noise cancelling headphones and other noise cancellation technologies. Some VFs do also have passively stealthy designs to complement their active stealth systems and have passive stealth coatings, but those coatings are a lot more robust since they have to stand up to things like atmospheric reentry.