A study of the abort rocket unit plume effects on the aerodynamics of the separation unit

To assure the safety of crews of manned transportation spacecraft during ascent in case of a launch vehicle failure, escape rocket units are used, which are designed to perform emergency separation of the re-entry vehicle with its crew from the launch vehicle and pull it away to a safe distance. At the same time, the escape rocket unit generates the required conditions for shockless separation of the re-entry vehicle and its nominal landing on the surface of the land or water. The action of the rocket unit is triggered by the abort command that can be generated by the launch vehicle control system at any point in the ascent trajectory starting from the lift-off. In order to size the rocket stage performance, to assures stability and controllability of the separation unit, which includes the escape rocket unit, a transfer compartment and re-entry vehicle, in free flight with both operational and non-operational main propulsion systems, one needs to know its aerodynamic properties in the flight range of Mach numbers М∞, angles of attack αn and aerodynamic roll angles n. In this connection, of greatest difficulty is the determination of the effects the jets of the rocket unit propulsion system have on the aerodynamic properties of the separation unit and gas dynamics effects of the jets on the surface of the re-entry vehicle. A study of aerodynamic properties of the escape system separation unit with operating propulsion system is a very challenging problem from both computational and experimental standpoints. The paper presents results of numerical studies of aerodynamic properties of the escape system separation unit for the new-generation Russian crew transportation spacecraft, as well as the validation of the results of computational studies using experimental data obtained from a scale model in wind tunnel. The studies were done in the range of subsonic to hypersonic flight velocities and variable levels of jet off-design condition.