Numerical and experimental determination of aerodynamic behaviour of the abort stack of the launch escape system for the new-generation crew transportation spacecraft

In the development of crew transportation spacecraft one of the most important tasks is to assure the crew safety in case of a launch vehicle failure during ascent. In order to rescue the crew in offnominal situations, launch escape systems are developed, which are intended for separating and moving the spacecraft away from the failed launch vehicle to a safe distance at any point in time between the lift-off and completion of the orbital insertion. To accomplish this task, an abort stack is formed within the launch vehicle which includes a rocket booster for emergency escape with a set of propulsion units, the crew transportation spacecraft and an adapter section between the escape rocket stage and the crew transportation spacecraft. This configuration was used in the abort stacks of escape systems for Soyuz, Apollo, Orion and other spacecraft. The distinctive feature of the new rocket booster for escape system of the crew transportation spacecraft, in comparison with the existing hardware, is its two-stage configuration, which allows rescuing the crew during virtually any phase in the ascent. An important stage in the development of the abort stack of an escape system and its sizing is the study of its aerodynamic behavior when thrusters are on and off during its free flight after separation from the failed launch vehicle. In recent years, computer simulations have been finding an increasingly wider use for aerogas dynamics studies of vehicles under design, since they have a number of advantages over physical modeling, especially in the early stages of design. Industrial use of computer simulations for aerogas dynamics studies implies a certain process, which includes the stage of preliminary testing of the software to be used against experimental data from similar vehicles. This paper discusses a sample application of such approach to the aerodynamics study of the abort stack of the escape system for the new-generation crew transportation spacecraft currently under development at RSC Energia. It presents results of computational studies with the use of two different software packages that were done at RSC Energia and TsNllmash, and their comparison against the results of model tests in wind tunnels of TsNllmash.