Hmmmm...no comments eh? PDE (Pulse Detonation Engines) have potential in 2nd generation CCEs (Combined Cycle Engines) that could someday make SSTO a reality.
The exhaust exits at up to an incredible mach 5, which means that a mere 5:1 propellant to payload+structure ratio would be required to achieve the mach 24 needed for orbit. This does not take into account air resistance, but it also does not take into account the fact that the PDE is an air breather during the early part of its ascent, cutting down even further on the initial propellant weight, by reducing the amount of oxidizer that has to be carried.
Here is another link, that goes to a PDF that describes a pure-rocket PDRE, which is strictly a rocket carrying all its own oxidizer. At a minimum, it eliminates the need for heavy turbo-pumps providing 2000 psi of pressure to the combustion chamber. In addition to this, the exhaust velocity of the PDRE is also enhanced, resulting in higher Isp, and thus higher payload-fraction to orbit.
Of course, practical application of both of these technologies is still many years away.
Nope. A pulse jet uses ordinary combustion -- the fuel is simply burned. Same with a turbo jet, or the engine in your car. A very fast, explosive-like burn but still well short of detonation. A pulse detonation engine combines the fuel and air in such as way as to create an actual detonation. I read about these in PopSci (or PopMech?) last year. Very exciting technology with the potential to revolutionize aviation. The noise is a big problem though.