Abstract:

Intense effects between rocket based combined cycle (RBCC) engine performance and vehicle flight trajectory cause the coupling between trajectory design and engine performance analysis. Ascent trajectory design method of RBCC-powered vehicle is studied and the Mach number-dynamic pressure reference curve method is propounded. Complement to non-uniform rational B-spline (NURBS) curve is made to define arbitrary dynamic pressure reference curve, with the selecting principles studied for the control variables of reference curve. Solving procedure for trajectory simulation is investigated with the binary-search method for angle of attack. Trajectory design and analysis for air-launching RBCC-powered vehicle are conducted with the proposed method. The results show that (1) Mach number-dynamic pressure reference curve method is suitable for ascent trajectory design of RBCC-powered vehicle, because it considers the coupling between engine performance and flight trajectory. (2) More than 50% of propellant consumption is produced at low Mach number stage (Ma<2.0) of ejector mode, dominating the performance optimization of RBCC engine. (3) Propellant mass flow rate in ejector mode reaches 6.3 between the maximum and the minimum. (4) Ram effect of the incoming air exceeds the pure ejection effect of primary rocket and becomes the dominant for air intaking in ejector mode with the flight Mach number over 1.7.

Key words: hypersonic vehicle, rocket based combined cycle, flight trajectory, control law, non-uniform rational B-spline