I don't think that necessarily tracks: having a test-bed be reusable can mean you get more flights, can carry more payloads, and study many different things. Wh

I don't think that necessarily tracks: having a test-bed be reusable can mean you get more flights, can carry more payloads, and study many different things. Which for exploring something as complex as hypersonic flight, has obvious attractions. The research vehicle that has done the most study of hypersonic flight to-date is almost certainly the North American X-15, which did 199 flights over 9 years, and it was fully reusable and not related to a weapon in any way. This presumes, of course, that the cost of turn-around for reflight is <<< the cost of building a new one. This is obviously true for normal airplanes but was probably only barely true for the Space Shuttle. So there is a continuum here, a point where the between-flight inspection and cleaning costs do loom large enough to not be worth it.