A systems engineering approach was used to produce a preliminary design configuration for an ion-propelled orbital transfer vehicle system. The four components of the system are: ground software, ground hardware, the orbital transfer vehicle and the space shuttle. The orbital transfer vehicle uses electrostatic propulsion to transfer payload satellites from a low earth orbit, to any other desired orbit. The system maintenance concept, and a conceptual design are derived from the statement of need and the system operational requirements. The resulting design, maintainability, reliability and support requirements are discussed. A discussion of the feasibility of an ion propelled orbital transfer vehicle is included. / Master of Science

A homotopy approach for solving constrained parameter optimization problems is examined. The first order necessary conditions, with the complementarity conditions represented using a technique due to Mangasarian, are solved. The equations are augmented to avoid singularities which occur when the active constraint set changes. The Chow-Yorke algorithm is used to track the homotopy path leading to the solution to the desired problem at the terminal point. Since the Chow-Yorke algorithm requires a fairly accurate computation of the Jacobian matrix, analytical representation of the system of equations is desired. Consequently, equations obtained using the true anomaly regularization of the governing equations were employed for the above purpose. A homotopy map suited for the space-flight rendezvous problem including a minimum radius constraint is developed, which can naturally deform any initial problem into some other valid desired problem. Several coplanar and non-coplanar solutions for circular and elliptic cases have been presented for the restricted time problem with a minimum radius constraint. / Ph. D.

The problem of developing a generalized impulse as a function of a set of parameters is investigated. The proposed generalized impulse alters an existing orbit by producing, over some period of time, a change in velocity, ΔV, as well as a change in position, Δr. The generalized impulse is described by parameters associated with an instantaneous change in velocity as well as parameters associated with an atmospheric skip trajectory. Closed form solutions are obtained through several changes of independent variable, the use of modified Chapman variables and the consequent analytical integration of the uncoupled equations. The closed form solutions contain between two and six parameters depending on the complexity of the desired skip trajectory. Fuel optimal transfer orbits are obtained using the generalized impulse along with Keplerian arcs and instantaneous changes in velocity. Families of coplanar and noncoplanar transfers for circular orbit to circular orbit are numerically generated. The generated transfer trajectories involve the rendezvous of two vehicles. The orbits are not globally optimal but rather optimal for the specified number and type of velocity impulses specified. The optimal solution to the nonlinear problem is determined via sequential quadratic programming which satisfies the Kuhn-Tucker optimality conditions for constrained minimization. It is found that for transfer between coplanar and noncoplanar orbits, solutions using the generalized impulse compare favorably with solutions obtained by optimal control theory. Numerical solution to complex problems involving transfer from general orbit to general orbit were not obtained. / Master of Science

In this work, we describe all the possible radiative processes occurring in a low temperature hydrogen plasma. Some of the fundamental concepts involving ionized gases and collision phenomena are presented, and a rigorous approach is used to show that classical mechanics is quite appropriate to our study. As an application to a laser engine, we investigate the effects of the maximum temperature, the temperature gradient, the stretching of the plasma shape, the engine pressure, and the equivalent sphere radius, on the total emitted power, including absorbing mechanisms through the equation of radiative transfer. Graphs related to spectral radiative exitances are included, and a complete set of graphs of the total power, permitting interpolations with respect to the above relevant parameters, are also provided. / Master of Science