Free-flight experiment and numerical simulation for cold thruster plume

An experiment, Astra-2, was performed at the space station Mir in 1995-1996 to study its ambient atmosphere parameters. For far-field plume research, the equipment of Astra-2 included a small cold gas thruster using a marked gas, argon. The results of this research offer a good basis for validation of various numerical approaches for plume flows, from simple engineering models to exact numerical approaches using a Navier-Stokes solver in the continuum regime and a direct simulation Monte-Carlo code in the near-continuum, transitional, and free-molecular regimes. A comparison of experimental and numerical results shows the necessity of accounting for argon condensation processes in the nozzle and in the vicinity near the nozzle.