The unique aspects of simulation verification and validation

Models and simulations (M&S) will be employed to support important design decisions and verification of system requirements in the development of NASA´s Orion Crew Exploration Vehicle. Most simulations are implemented in software. For developed software, NASA´s software engineering procedural guideline NPR 7150.2 and safety standard NASA-STD-8719.13B apply. Recognizing the need for critical M&S to be validated to be credible for their intended uses, NASA developed a Modeling and Simulation Standard, NASA-STD-7009. This paper analyzes the requirements specified by these standards and their role in test, validation and certification of modeling and simulation software. It discusses simulation validation as a distinct instance of software validation with corresponding unique requirements. Simulation-specific validation concerns include fit to intended use, validation against experimental data, uncertainty quantification, and sensitivity analysis. The paper also describes the Orion M&S verification, validation, and accreditation (VV&A) process.