Orbital Analysis of a STS (Space Transportation System) External Tank in Low Earth Orbit.

By flying a different launch profile, it is possible for the Space Transportation Systems Orbiter to bring the External Tank directly into space. Many studies by NASA and private industry have detailed the potential on-orbit uses of an External Tank. However, at space shuttle operating altitudes, an orbiting tank will experience multiple environmental forces resulting in its decay into the lower atmosphere and eventual re-entry. This thesis conducts a preliminary study of a single external tank in low earth orbit. Criteria for a parking orbit are defined and, using an orbit prediction computer program with atmospheric drag and gravitational perturbations included, a search is made for the lowest initial altitude that will allow the external tank to remain in this orbit window. The starting altitude that meets the orbit requirements is found to be within reach of the shuttles capabilities. The orbital elements of this parking orbit are then analyzed and a method for quick calculation of these parameters is devised. An evaluation of the factors that affect the orbital contraction of an external tank is also performed. The atmospheric density and the tank characteristics can both contribute to high orbital decay rates. Keywords ASAPArtificial Satellite Analysis Program Orbit prediction computer programs Trajectory analysis Satellite orbits Satellite drag Gravitational perturbations, Orbital elements.