A horn is an excellent way of mating high pressure on the surface of a cone with the atmosphere - and is about the same idea as a 'complete' torpedo shape, but we don't have the luxury of bringing our functional, parkable road cars to a point at the tail with a slope that works at highway speeds. You can fold a horn without losing much of its effectiveness - clearly a luxury much less available on cars unless you want to model your tail after a
collapsible cup and use a ram of some sort to suck it in when you slow down.
A horn is kinda the point though, rather than pushing a moving wave past stationary surfaces in air, we're pushing surfaces through air. The need to manage pressure differentials isn't terribly different in either case. So since we can't really make a full horn (20 foot long tail) , the whole point of this thread is what can we do in a shorter space to get the same effect as a horn?
Good to see we're still tossing ideas about
