The present invention models dynamic behavior of flight vehicles for simulation, analysis, and design. The present invention allows a user to define the complexity of a flight vehicle model, and such models may be simple rigid body models, models of medium complexity, or very complex models including high order dynamics comprising hundreds of structural flexibility modes and variables related to aero-elasticity, fuel sloshing, various types of effectors, tail-wags-dog dynamics, complex actuator models, load-torque feedback, wind gusts, and other parameters impacting flight vehicles. The present invention accommodates and analyzes multiple vehicle and actuator concepts and configurations as defined in flight vehicle input data, which specifies flight vehicle parameters at a steady-state condition for modeling flight vehicle response to dynamic forces and flight control commands with respect to steady state operation.