Book excerpt: A method for calculating structural loads in a rocket engine-actuator-vehicle system is developed. The engine is attached to the vehicle by a universal-type gimbal joint and by two actuators. The engine is assumed to be a rigid body. Either the actuator loads or the engine angular acceleration is assumed to be known with a calculation of the other required. A set of algebraic equations is developed from which the unknown actuator loads or angular acceleration and the forces and moments at the gimbal point can be calculated . I.