I'm sure there's been at least research in this area since the 1980s - I remember hearing about it when I worked in the Defence industry on weapons systems in t

I'm sure there's been at least research in this area since the 1980s - I remember hearing about it when I worked in the Defence industry on weapons systems in the early 2000s as an improvement over the default static "Spike" on existing high-mach-number vehicles (ICBMs for example)... As mentioned in the other comment, Supercavitation for torpedoes have existed for a while, which in some ways can likely be argued to be similar (altering the medium the body is in to reduce drag).