Jet interaction at supersonic cross flow conditions

Abstract

The thrust produced by lateral jet systems has been successfully used for several years to control the flight trajectory, i.e., the maneuverability of spacecraft in the high atmosphere and in orbit. Recently this technology has also been applied to projectiles and rockets flying in the low atmosphere from sea level up to more than 10 km. At ISL, investigations have been performed with a 90 mm caliber full-scale projectile in order to study a special side jet controlling system at flight speeds of about 1500 m/s, i.e., Mach number $M \approx 4.4$ at altitudes of 1.5 and 7.5 km. The High Energy ISL Shock Tunnel facility is used as a ground testing facility in which the flow around the projectile is studied at fully duplicated flight conditions. In the test facility the projectile is fixed inside the test chamber and the atmospheric air is set in motion flowing around the projectile test model. The air flow is generated in the ISL Shock Tunnel STB which is equipped for this purpose with a divergent square nozzle with an exit side length of 184 mm. A lateral gas jet is produced by combusting a solid propellant in a combustion chamber, placed inside the projectile. The powder gases are blown out laterally via a nozzle, creating a complex flow field by the interaction of the lateral jet with the external cross flow. Differential interferometry is used to visualize the behavior of the external flow field distorted by the lateral jet outflow. Numerical simulations have been performed based on steady state computations using the conservation equations of mass, momentum and energy. This was done to theoretically predict the development of the flow field around the projectile under the influence of the side jet. As final result the lateral force acting on the projectile is given as force and moment amplification factors, KF and KM respectively.