An Eclipse Based Software Solution for Space Mission Design

Kurzfassung

Many experts are needed to design a spacecraft. Each of them is responsible for a specific sub system, such as power, propulsion or configuration. These subsystems have strong dependencies among each other. For example, just a small change in the spacecraft's mass can lead to a change in its size. Changing the size, however, may require a different rocket to launch the spacecraft, which in turn may not be able to reach the designated orbit. In the classical, serial design approach, all experts worked on their specific part of the problem on their own. When finished, they passed on their results to the next expert until everyone had contributed to the overall design. As a consequence, several months were needed to complete a design. Today, spacecraft design is based on concurrent engineering (CE). All subsystem experts work on their part of the problem in parallel. Additionally, they continuously verify that their work does not conflict with the design choices by others. For this kind of cooperative work, the German Aerospace Center (DLR) operates a Concurrent Engineering Facility (CEF). At the CEF the experts meet for design sessions of typically two weeks' time. Each workplace is equipped with a computer that runs the design tools required by the corresponding subsystem. All computers share their results via a central data repository. So far, Excel used to be the standard tool for data collection and exchange. This choice, however, proved to be unsatisfactory in various ways. For example, Excel did not support the design data exchange between disciplines well. For this reason, DLR started a software development based on the Eclipse Rich Client Platform. Although this platform provides little support for the specific engineering tasks of the experts, many open source tools for concurrent and distributed work have been developed over the years, and Eclipse integrates many of them into a smooth workflow. This makes Eclipse a perfect match and baseline for the DLR design tool for space missions. The core of the new software is an EMF-based data model that serves two purposes: First, it is used as starting point for Model-Based Software Engineering, where a range of EMF-related features are very useful, such as the EMF Edit Framework and XML serialization. Second, the data model supports Model-Based System Engineering by providing semantics and consistency to the expert's data. Thus it can be reused for parameterizing further engineering tools such as simulations of the subsystems or the whole spacecraft. In a CE session all experts use local instances of the design software. The output of each instance contributes to the common, distributed data model which is shared by a Subversion server in the background. The details of the data exchange are hidden from the experts. They only see two functions in the user interface for "update" and "commit", which they use whenever necessary to contribute changes to the study, or to receive updates from others. As compared to the Excel-based tool, the new CEF software proved to be superior in terms of functionality, reliability and extensibility. In this talk, we give an overview of our software development, with emphasis on the data exchange among the experts. We comment on the strengths and weaknesses of Eclipse in respect of our work.