Vehicle flight simulation is an important part of the innovation of aerospace vehicle technology. The NASA Engineering Safety Center (NESC) has identified and addressed the need to verify flight vehicle simulations through their work on the “Six degree-of-freedom (6-DOF) Flight Simulation Test Cases.” The author was prompted to develop tools that would allow for the rapid implementation of simulations for novel vehicle concepts including hypersonic re-entry vehicles and urban air mobility vehicles.
This software library leverages open source scientific computing tools to implement an efficient simulation framework for flight vehicles in Python. Equations of motion are composed in blocks using the SimuPy library, an open source Python alternative to Simulink, and integrated using SciPy’s wrappers for standard Fortran implementations of ordinary differential equation solvers. Dynamics equations of the inertial state variables for the position, orientation, and their corresponding rates for integration are developed using the SymPy symbolic library and implemented using code generation. Kinematics equations are implemented through symbolic definition and code generation as well as leveraging other open source software that implements useful functions, such as the solutions to the inverse geodesy problem.
A number of the NESC Atmospheric test cases have been implemented to verify the implementation and derivation of the equations of motion. These are located in the nesc_test_cases directory. To run, simply execute any of nesc_case##.py files or the run_nesc_cases.py which will iterate through test cases that have been implemented. These scripts will attempt to load the NESC reference results from the parent directory and plot the results along with the results from the SimuPy implemntation. To include the NESC results in the comparison plots, download the Atmospheric trajectory data and unzip the Atmospheric_checkcases directory to the root simupy_flight directory. You can place the Atmospheric_checkcases directory in different location by changing the data_relative_path variable in the nesc_testcase_helper.py script.
This software is released under the NASA Open Source Agreement Version 1.3.
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