Detailed simulations of the Space Shuttle hydraulic system were developed to verify that all control functions could be performed under all unique conditions encountered during a space mission. These simulations have been used to analyze dynamic problems which could have threatened to destroy flight or test hardware.
The RoHDA program was developed to analyze pressure transients in the time domain when the disturbances of interest occurred at frequencies below 100 hertz. The HSFR program was used to analyze transients that occurred above 100 hertz. This program operates in the frequency domain.
These programs were utilized on a digital computer to verify that the hydraulic system of the Space Shuttle Orbiter was ready to fly.