2. Planning Space Campaigns and Missions

Space missions are described by “architectures” that define the vehicles and their trajectories, and their scheduling, with key parameters such as mass, volume, power, … given at each step. An architecture can be described in terms of a series of states connected by steps. A state is a condition of relative stability and constancy. A step is an action of change (e.g. firing a rocket). In the early stages of designing a mission to Mars, an important rough measure of the mission cost is the initial mass in LEO (IMLEO). A significant portion of this mass consists of propellants. Using state-step data, one can estimate the initial mass in LEO for delivery of payloads to Mars orbit and the Mars surface. In any mission design, the first and foremost thing that is needed is the set of imparted changes in velocity (Δv) for all the mission steps. Estimates of Δv for various steps can be made by standard trajectory analysis. The propellant requirements for each step can be estimated from Δv using the rocket equation. Unfortunately, in recent NASA reports describing planned space missions, ferreting out state-step information is at best, time-consuming and frustrating, and often not there. Therefore, it is typically difficult (if not impossible) to trace through the steps of NASA concepts for human missions to Mars.