In this paper, we calculate the collision between a low density flyer and a very high density target. The shock wave parameters in this case are calculated for the first time. The results are shown in Figs. 3e5. Upon impact one gets two shock waves, one into the target and the other one into the flyer. The shock wave in the low density flyer is relativistic with a shock velocity of the order of the speed of light while the shock wave in the target is not relativistic although it has high velocities of the order of few percent the speed of light. The formalism of relativistic hydrodynamics is important also for the target since for an ideal gas equation of state the compression of 4 is immediately achieved unlike in the nonrelativistic case where an infinite pressure is required for this
compression.