7. Mission Design

During the entire phase of space transportation system mission, from lift-off till satellite injection, various constraints and requirements applicable not only to the mission but also to vehicle systems, ground systems, range safety and tracking systems are to be satisfied. Considering these constraints and requirements, an optimum feasible trajectory has to be designed to meet the mission requirements. The mission design process involves the utilization of the available energy for realizing the defined orbital mission by devising suitable strategies of directing the energy along the suitable path and sequencing the energy addition process. Optimum mission design strategies have to be arrived at to achieve the maximum performance, ensuring the defined mission under nominal and off-nominal flight environments and system parameter dispersions. The trajectory shaping satisfying vehicle loads and radio visibility for continuous tracking coverage during ascent phase are other essential parts of mission design. There are number of constraints like thermal loads on the spacecraft, the vehicle subsystems during ascent phase and jet plumes of reaction control system thrusters interacting with the spacecraft. The passivation requirements of the final stage after spacecraft separation are to be carefully worked out. Another important aspect of mission design is to finalize the flight events/sequences which generate various commands to separate the stages and to initiate the subsequent flight events. In such complex systems close interactions among various disciplines exist, and the mission design requires several iterations. In this chapter all these aspects of mission design are discussed in detail and various activities involved in mission design process explained. The mission design strategies and importance of the same for the vehicle design process are included. Mission requirements, constraints, design and analysis aspects and trajectory design constraints during various phases of trajectory are presented. Mission sequence design considerations and all other mission-related studies like satellite orientation requirements for multiple satellite launch and passivation requirements to ensure the safety of the spent stage are also highlighted.