1316. Space Shuttle Intregrated Mass Properties for Ascent Trajectory Programs

Paper

Abstract

This paper presents the method of integrating a mass properties determination in an ascent trajectory computer program. Unlike the conventional tandem launch vehicle, the Space Shuttle configuration consists of a hybrid airplane spacecraft mounted on a large external tank. The Space Shuttle is launched into earth orbit by a combination of three liquid propulsion engines mounted in the Orbiter and two solid rocket motors attached to each side of the External Tank. During ascent phase, the main engines and solid rocket motor nozzles are gimbaled to track the vehicle center of gravity. In the flight control system the response is a direct function of the moment and product of inertias. Therefore, in order to simulate the ascent trajectory with a mathematical model, the mass properties of the Vehicle as a function of time mu?;t be integrated with the trajectory equation to improve the accuracy of the calculations. A complete six-degree-of-freedom .mathematical model would not be acceptable without integrating the mass properties with the equations of motion.
The Space Shuttle is a complex flight vehicle comprised of four major elements: Orbiter, External Tank, Main Engines, and Solid Rocket Boosters. In order to integrate the mass properties with the ascent trajectory mathematical model, a routine was developed which utilizes the standard weight summation, moment, moment of inertia, and product of inertia equations to combine the mass properties of the elements during the ascent phase of flight. An additional routine was developed containing the sequential mass properties of the elements. This routine is made up of data banks for various element weights, center of gravities, moment of inertia, and product of inertia.
These routines, in subroutine format, have been incorporated in the Rockwell Shuttle Ascent Performance Evaluation (SHAPE) computer program.