Smoothed Particle Hydrodynamics numerical method is extensively used in the study of hypervelocity impacts and subsequent shock propagation into solids. During impacts into inhomogeneous materials, effects produced on the interface of adjacent materials by shock waves need to be resolved. The present study discusses an SPH multiphase scheme for compressible processes, that is based on the number density estimate and exhibits the scheme’s performance at shock propagation through inhomogeneous materials. In specific, a one-dimensional Riemann problem with known solution validates the scheme and results of two-dimensional hypervelocity impact scenarios into materials with (large-scale and small-scale) inhomogeneities are studied