Аннотация:We study axisymmetric time-dependent problem of reflection of a shock wave running into the wall with a shortorifice and associated rarefied gas flow into vacuum through a pipe. The main characteristics under consideration are the mass flow rate through the pipe and its transition to the constant value, the influence of theorifice presence, pipe relative length and Knudsen number on the reflected shock wave velocity. The analysis isbased on the numerical solution of the S-model kinetic equation using the second-order accurate finite volumemethod, implemented into the “Nesvetay-3D” software package