An implosive shock wave on a based gas the particular case of motion with zero pressure, but with variable density is discussed. The density is described by degree relation to distance up to a point of focusing of a shock wave. Such selection of an exponent in this relation that the entropy in all area of flow after passage of a shock wave was a constant (homentropic case) is offered. Thus qualitatively different behaviour of temperature in comparison with classical case Guderley – Landau – Stanjukovich is obtained.
