4. Space Transportation Requirements and Launching of Satellites

The function of space transportation system is not only to lift the specified satellite from Earth surface, travel through space and to inject it precisely into the defined orbit but also to achieve all specified orbital specifications simultaneously. To achieve these objectives, the STS has to provide the required mechanical energy to the satellite, defined by the orbit size and satellite mass. It is also necessary to have an optimum location of launch site on the surface of the Earth and launch direction (launch azimuth). Therefore, each orbital mission demands specified location of launch site and launch azimuth. But, due to geographical constraints, it is not possible to have an optimum launch site, and the allowable launch azimuth directions are also limited due to range safety related issues. In such cases, launch vehicle has to provide extra energy to reach the defined target. The influence of Earth’s gravity field and aerodynamic drag during atmospheric flight phase causes the energy loss and to compensate these losses extra energy has to be provided. All these effects need to be considered for configuring STS to provide the necessary energy to the satellite. The satellites requirements are widely varying, ranging from low Earth orbits to high altitude orbits, depending on their applications. Therefore with the effective utilization of available energy in the STS, the maximum performance has to be achieved by adopting suitable strategies and the details of all these methods are explained in this chapter. The functional requirements for STS design have to start with the orbital mission requirements and the satellite mass to be placed in the specified orbit. The step by step procedure starting from mission design to STS design process, which satisfies the overall functional requirements, is also described. Various errors occurring during the operation of several subsystems of STS, their effects on overall mission and how to alleviate them are also explained here.