The PDE technique offers one solution to the problem of hypersonic
thrust - burning the fuel-air mix in the millisecond or so of time
available. Consider the fact that the fuel-air mix has to combust and
go through the engine faster than the vehicle is moving or the
incoming air just piles up and you don't get any thrust. A rocket
doesn't have this problem. Detonation occurs much faster than
combustion - and if the duct is acoustically resonant (there's a nice
problem with changing velocities!) the engine will be maximally
efficient. Even if it never flies it'd be a good addition to a rock
concert.
Walt BJ