I didn't know this site could be so philosophical. I might enjoy these kind of discussions as well, even if I can appreciate that they aren't always useful.
I think a "model rocket" is a model rocket as long as it
1. was built to resemble a rocket or to manifest the basic functionality of a rocket;
2. fulfills all of the criteria of the Platonic Form of "rocket" (see
Phaedo);
3. looks, smells, tastes or generally conceives as a "rocket" in "model" form;
4. looks cool on a shelf. Q.E.D.
"Model Rockets" shouldn't have to fly to be subsumed under the "model rocket" rubric. Unbuilt model rockets, i.e., still in kit form, are "potential" model rockets, whereas built model rockets have fulfilled their potentiality, but not as much as model rockets that
a. are intended to fly; and
b. have actually flown, whether successfully or not. This leaves us with the following subsumations:
i. model rockets (includes actualized, potential, flown or unflown);
ii. potential model rockets, generally
unflown.
iii. actualized model rockets,
unflown, unintentionally or intentionally;
iv. actualized model rockets,
flown, unintentionally or intentionally. "Model rocket" as a signifier subsumes all of these categories in all various forms and substances. Normative valuations between these various manifestations will vary widely, but
actualized, flown model rockets extend more towards the ultimate Good than the other previously delineated forms. Q.E.D.