Some problems concerning the explanation of the fact that regular reflection of shock wave from the axis of symmetry is impossible are considered. This fact is well-known and can be demonstrated by linear analysis; it was proved in /1/ by integrating the compatibility condition along the characteristic reaching the point of alleged regular reflection. In this paper, we investigate the flow in the neighbourhood of this point and show that it should be conical. We also prove that the inverse problem of constructing the flow field and the boundary streamline from a given shock wave of arbitrary shape is physically unrealizable in a small neighbourhood of the axis of symmetry. This topic is also relevant because the literature contains conflicting statements claiming that regular reflection is possible and (much more seldom) impossible, never offering a detailed explanation (see, e.g., /2, 3/). This may explains why this topic has not been treated in detail in authoritative monographs, unlike the similar problem of the collapse of an unsteady-state spherical or cylindrical shock wave.
