Investigation of flight dynamics and effects of rotational degrees of freedom on the flight performance of asymmetric space transportation systems based on the SpaceLiner 7 concept

Abstract

The SpaceLiner 7-3 is a concept for a suborbital spacecraft, which is capable of transporting 50 passengers over ultra-long-haul distances. Since 2005, this concept is has been researched by the German Aerospace Centre (DLR). This study analyzes the flight dynamics of the vehicle during its ascent flight of the reference mission from Australia to Europe. Key point of this study is the development of a flight dynamics simulation of the SpaceLiner, which can determine the evolution of all rotational and translational states of the vehicle. For the flight dynamics simulation of the SpaceLiner, the model definition of the vehicle has been extended from previous studies. Estimations of the vehicle’s moment of inertia are conducted, as well as a draining model of the propellant tanks is determined. Also the aerodynamic database of the SpaceLiner is extended by lateral and dynamic derivatives. In order to determine the control deflections of the thrust vector control during simulation, a flight control model for the SpaceLiner Vehicle is developed. The control design process for this system is automated by the relay auto-tuning method. The flight dynamics model of the SpaceLiner, as well as the corresponding flight control model, is included into a newly developed 6 DOF trajectory simulation, implemented in Simulink. This simulation features numerically robust calculations of the vehicle’s state vector in arbitrary flight conditions. The validity of the implemented simulation is proven in a cross-validation test against the commercial tool ASTOS. Based on the developed flight dynamics simulation, analyses of the flight dynamic characteristics of the SpaceLiner are performed. The aerodynamic stability and trimmability of the vehicle is determined for a nominal ascent flight. The nominal ascent trajectory is also simulated and deviations in respect to a 3 DOF reference trajectory are identified. Furthermore, first analyses of ascent trajectories under wind loads are conducted. Based on the simulation results, the feasibility of the implemented thrust vector control is reviewed.