Advanced Spacecraft Systems Design using Model-based Techniques

Abstract

The paper gives an overview of the current activities at the German Aerospace Center (DLR) regarding modern design methodologies for future space missions. It outlines the principle vision of Model-based Systems Engineering and describes the expected momentum in the context of spacecraft design. DLR develops a software framework called Virtual Satellite to embody MBSE techniques for future projects. The core element is a system model which is used as common data basis for all involved stakeholders. The key achievement was the successful introduction of the Virtual Satellite as an integrated design tool in early design phases which are nowadays mainly carried out as concurrent design studies. The paper introduces the framework and highlights in brevity some of the most important MBSE approaches which are: Design support by semantic models: Within our studies, all design values are entered with a relation to a standard system of unit definitions. This reference to an underlying standardized semantic model brings certain benefits for users. Firstly, they can work in their preferred system of units. The software takes care of all conversions automatically and assures consistency, e.g. respects the common approach of only using SI units in the design. Secondly, it enables sanity checks on entered equations, e.g. verifies the cancellation of units in a division and checks it against the expected unit of the result. System analysis: Having a system model with all design values and the behavior (analytic equations) paves the way for running certain analyses on the model to evaluate the performance, and thus, to judge the feasibility of the design with respect to the requirements. Analysis in this context has a broad meaning. It starts with simple static views on the data like the mass or power budget or the interactive visualization of the configuration of the spacecraft. It also covers sensitivity analysis to identify design drivers and guide the study team with informed decisions. One of our big goals for future system analysis is to develop means for automatic verification of the mission and the incorporation of the behavior of the system (e.g. with simulation models) Automatic Generation of Artifacts: The automatic generation of project related artifacts has a strong analogy to Model-driven Architecture in software engineering. Here, the prospect of the model is that recurring tasks are automated. For instance, the documentation or interface control documents can be derived from the system model and are kept consistent throughout the design process. Another example is the generation of the geometric model which is used as input for domain specific analyses like thermal or structural analyses of the spacecraft. In later phases, the model can also be used to generate on-board software for the spacecraft. Thus MBSE is considered to be an essential enabling technology to meet requirements of the growing complexity of future distributed mission concepts or system-of-system designs.