Orbital transfer optimization for LEO satellites

• Autor(a) principal: Santos, João Miguel Caetano dos
• Data de Publicação: 2023
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.6/13961
• topic: Transferência de Orbita Terrestre Baixa; Transferência Não-Hohmann Leo; Transferência Orbital Não Coplanar; Transferência Orbital Ótima; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia Aeronáutica

Orbital transfers are important because they allow us to perform a transfer between two orbits at different altitudes, inclinations, or eccentricities using an intermediary elliptical orbit, orbit transfers can be used to re-orbit satellites or even intercept missiles, in this dissertation we studied different methods of performing these Orbital transfers. We can divide the orbit transfer into two main categories, the classic methods and the non-classic methods. The classic method also known as the Hohmann orbit transfer was described in 1925 by Walter Hohmann, the problem with this method is that it has the restriction of the orbit transfer having to start in the apogee or the perigee of the initial orbit and ending at the perigee or the apogee of the final orbit respectively. In order to bypass these problems, we use the non-Hohmann orbit transfer which allows us to execute the orbit transfer starting at any point of the initial orbit and finishing at any point of the final orbit, minimizing the cost function. The main objective of the thesis is to find the method for each type of orbit transfer minimizes the global energy used without having the limitations of the normal methods such as the Hohmann transfer. In the dissertation we will study three cases, the coplanar Hohmann transfer orbit, the coplanar non-Hohmann transfer orbit, and the non-coplanar non-Hohmann transfer orbit. In order to model these orbit transfers we used GMAT (General Mission Analysis Tool) which is a tool of NASA that allows the user to create an orbit transfer between two orbits chosen by the user. In the non-Hohmann cases the state variables used in the coplanar cases were the radius, the true anomaly, the radial velocity and the transverse velocity, the control variables were the acceleration and the control acceleration direction. For the non-coplanar case the state variables were the spherical coordinates of position and the spherical components of velocity, the control variables were the acceleration and the thrust direction angles. The results obtained were satisfactory despite in some graphs the results having some bumps at the beginning and end of the transfer orbit that was because of the low number of iterations.