6DOF Check Cases

This article is from the 2024 Technical Update.

In 2015, the NESC released benchmark Earth-based check-cases for well specified, rigid-body, six-degree-of-freedom (6DOF) aero/spacecraft models to promote consistent and accurate flight simulations across multiple Agency tools and facilities. Recently, the NESC expanded upon that effort to add Lunar-based check-cases to support new lunar exploration initiatives. This study produced a smaller, focused set of cases that exercise new and unique features of missions in the lunar environment in comparison with 8 high-fidelity NASA simulation tools and provides a measure of validation for simulations supporting Human Landing Systems.

TB 24-04 The participating 6DOF simulation tools include:

Results
The primary output of the check-cases is a time history of each output variable, which can then be plotted with any data plotting software. For simulation comparison, the results from multiple simulations are
plotted together. A static website was developed as a tool for the simulation groups to perform quick data comparison using interactive plots,access scenario specifications, and catalogue the results.

Example Comparisons: Case 5 (HLO) Sun Pointing Angle (pitch component) Regarding Vehicle Frame

The Initial Comparison plots show the simulations were not implementing Check Case 5 correctly, or had other issues. The Final Comparison plots show identical results once corrections were implemented to the simulations, indicating the importance of using check cases.”

Benefits for the FM Community
Utilizing benchmarking check-cases improves the simulations being assessed, reduces errors, builds confidence in solutions, and serves to build credibility of simulation results per NASA Standard 7009A Standard for Models and Simulations. Simulation comparisons can benefit from utilizing common standards for defining parameters and sharing models and elevates the validation for critical simulations used to support insight or requirement compliance through analysis.