One of the most important steps in designing any space mission is precisely determining the trajectory that the spacecraft will follow en route to its final destination. It is obvious to say that the success and even the feasibility of any mission depends primarily on a good design of its trajectory.
Two essential design parameters will result from the adoption of a certain class or trajectory for a mission : the overall time of the mission, including transit and eventual stays or orbits and the propulsion requirements to achieve the desired trajectories and orbits.
These two parameters are absolutely critical in the design of any mission, for they affect the human factors (medical, supplies, psychology) and the hardware requirements (propulsion, engines, systems, etc.) of the mission.
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