Spacecraft propulsion system simulation using three-stage decomposition method

Аuthors

Petrov D. S.

e-mail: dmitry.s.petrov@engineer.com

Abstract

Simulation is well known and highly used instrument for majority of space mission control tasks. Special software tools are used for development of spacecraft simulation models. These packages consist of a number of simple elements and algorithms designed for such elements synthesis. But some disadvantages were found in existent tools. The article is devoted to the new simulation models development method without such disadvantages. This method is based on structural decomposition into the simple models with one or a few short equations.
Presented in the article method uses three-stage structural model decomposition. Spacecraft dividing circuit into elements level is used as a scheme for first stage, each model element is separated to the simple models (SM) at second stage, and at the last stage each SM is divided to set of fragments. SM is a model of element details (such as iron bolt or electric cable) and SM fragment describes SM participation in concrete physical domain (e.g. electrical or mechanical). Represented decomposition scheme provides three radically different viewpoints: on each element of dividing circuit, on entire spacecraft scheme of concrete physical domain and on cross-domain interactions. Pairs of SMs could be linked with bonds. Each bond transfers parameters values between connected SMs.
Element model contains a number of interfaced and internal SMs. Interfaced SMs could be connected with other models of SMs elements and internals describe elements behavior. Models of elements of the same dividing circuit level could be combined into a model of spacecraft subsystem or system. Equations of different models could be computed on different processor units and cooperated with bonds mechanism.
Each SM with fragments contains one or few short equations of specified physical domains and cross- domain interactions. Models of elements could also contain the short particular equations to specify its behavior. Generally, such equations are logic, algebraically non-linear or have the first order differential as it mentioned in the article. Set of equations could be numerically solved with well-known math methods.
The article describes the process of abstract spacecraft propulsion system model creation. Definition of model parts including fragments, significant parameters, formulas and bonds is exposed. Examples of code are given. Propulsion system specific processes simulation graphs are shown.
With presented method it is possible to develop modern software tool for subsystem and entire spacecraft simulation. Models under creation will be tunable, inter- operable, scalable and re-usable. Such models will be useful for spacecraft mission control tasks and, especially, for integrated model-based health management.

Keywords:

simulation, spacecraft, mission control, model development, structural decomposition, modeling language

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