Effects Of The Rotational Vehicle Dynamics On The Ascent Flight Trajectory Of The Spaceliner Concept

Abstract

During the preliminary design of space transportation systems the vehicle dynamics are commonly reduced to a point-mass model for definition of the flight trajectory. While this approach effectively reduces the number of model parameters in the design process, it neglects the rotational dynamics of the vessel completely. Since the rotational degrees of freedom (DOF) have a significant influence on the vehicle's controllability, a sole analysis of the translational dynamics is insufficient to assess the general feasibility of the concept. This study investigates the ascent flight trajectory of the SpaceLiner vehicle, a concept for a hypersonic suborbital space plane, based on a newly developed 6-DOF flight dynamics simulation to determine the influence of the rotational dynamics on the vehicle's controllability and performance. The first part of this paper will focus on the developed vehicle model which features a transient inertia model as well as an algorithmic-designed flight control system. The second part will present several simulations of nominal and off-nominal ascent trajectories. Based on the results it will be shown that SpaceLiner's thrust vector control system is sufficiently dimensioned for the investigated mission scenarios, while the vehicle performance is only slightly influenced by the rotational dynamics.