Compressible fluid response to extremely rapid thermal power deposition.

``Gasdynamics of explosions is{\ldots}best defined as the science dealing with the interrelationship between energy transfer occurring at a high rate in a compressible medium and the concomitant motion set up in the this medium'' (Oppenheim, A.K.and Soloukhin, R.I.,1973, ``Experiments in Gasdynamics'', Ann. Revs. Of Fluid Mechs., \textbf{5}, 31-55,). Asymptotic modeling is used to show that the interaction depends on the ratio of the dimensional time scale for substantial chemical heat release, t$_{H}$', into a local region of length scale l', and local acoustic time t$_{A}$'= l '/a' where a' is the local speed of sound. When t$_{H}$'/t$_{A}$'$<<$1 local heat addition occurs in a nearly constant volume process (local inertial confinement) with a low Mach number fluid response. The temperature rise is accompanied by a concomitant pressure rise, so that for a brief instant a hot, high-pressure spot exists in a relatively low pressure and temperature environment. Subsequent expansion of the spot on the t$_{A}$'-time scale, driven by the large pressure gradient between the spot and the environment is the source (``piston'' effect) of compression waves in the environment. Wave coalescence can lead to shock wave formation.