Design process of a reusable Space Tug based on a Model Based approach

摘要

In the last years, space agencies are showing an increasing interest in space tug systems concept for a large range of future applications. The space tug is a spacecraft able to transfer payloads from Low Earth Orbit (LEO) to higher operational orbits. It allows the reduction of the spacecraft mass because some subsystems decrease in term of complexity (i.e the propulsion system), and the improvement of the spacecraft payload/platform ratio. The present paper deals with the design of a space tug involved in on-orbit satellite servicing missions. The design process is led following a proposed Model Based System Engineering (MBSE) tool-chain. This solution allows an effective classification, traceability and verifiability of requirements among the various phases of the design process, combining the main features of specific tools and software, such as Doors, Rhapsody, and Simulink. The crucial point is to guarantee by automatic exchange of information and models among the different phase of the product life cycle. The paper shows the design at different levels: mission and stakeholders analyses, functional analysis, concept of operations, the space tug logical and physical architectures and the sizing of the main on board subsystem. The details of the recursive process of requirements definition is provided highlighting how they derive from the mission scenario, the mission architecture, the concept of operations and the functional analysis and, in general, how the proposed sequence of tools simplifies and gives effectiveness to the design.