European Space Agency's launcher multibody dynamics simulator used for system and subsystem level analyses

摘要

Virtual simulation is currently a key activity in the specification, design, verification and operations of space systems. System modelling and simulation support in fact a number of use cases across the spacecraft development life cycle, including activities such as system design validation, software verification and validation, spacecraft unit and sub-system test activities, etc. As the reliance on virtual modelling, simulation and justification has substantially grown in recent years, a more coordinated and consistent approach to the development of such simulation tools across project phases can bring substantial benefit in reducing the overall space programme schedule, risk and cost. By capitalizing on the ESA (European Space Agency) Structures and Mechanisms division's strong expertise in dynamics (multibody software), a generic multibody flight simulator was created to simulate a wide variety of launch vehicle dynamics and control problems at system level since 2001. The backbone of the multibody dynamics simulator is DCAP (Dynamic and Control Analysis Package), a multibody software, developed by ESA together with industry, with more than 30 years heritage in space applications. This software is a suite of fast, effective computer programs that provides the user with capabilities to model, simulate and analyze the dynamics and control performances of coupled rigid and flexible structural systems subjected to possibly time-varying structural characteristics and space environmental loads. The simulator uses the formulation for the dynamics of multi-rigid/flexible-body systems based on Order(n) algorithm. This avoids the explicit computation of a global mass matrix and its inversion, and the computational burden in these schemes increases only linearly with the number n of the system's degrees of freedom. A dedicated symbolic manipulation pre-processor is then used in the coding optimization. With the implementation of dedicated interfaces to other specialised software (such as NASTRAN, CATIA, MATLAB/Simulink, etc.), it is possible to reproduce in detail most of the key subsystems and disciplines (such as trajectory, structures, configuration, mechanisms, aerodynamics, propulsion, GNC, propulsion, etc.) of the launcher in a single simulation. The simulator has been also tuned in order to be used in the studies on new launch vehicle feasibility concepts performed at ESA's Concurrent Design Facility. Furthermore, the code has been adjusted to tackle specific events, such as multi-payload separation dynamics (Swarm, Galileo, etc.), thrust vector control subsystem studies (such as GSTP3, GSTP4, Vega), lift-off analysis (such as Vega, etc.), general loads (Vega, etc.). In this paper, an overview of the launcher multibody dynamics simulator capabilities is presented by illustrating some examples.