Optimal low-thrust trajectories for nuclear and solar electric propulsion

• Low-thrust trajectories are usually optimized assuming constant power.
• Power is assumed to be a known function of the distance from the Sun, as for SEP.
• The whole journey from LEO to orbit about the arrival planet is here considered.
• S/C optimization is obtained as a function of the power generator mass density.
• Some example shows a comparison between SEP and NEP.

The optimization of the trajectory and of the thrust profile of a low-thrust interplanetary transfer is usually solved under the assumption that the specific mass of the power generator is constant. While this is reasonable in the case of nuclear electric propulsion, if solar electric propulsion is used the specific mass depends on the distance of the spacecraft from the Sun. In the present paper the optimization of the trajectory of the spacecraft and of the thrust profile is solved under the latter assumption, to obtain optimized interplanetary trajectories for solar electric spacecraft, also taking into account all phases of the journey, from low orbit about the starting planet to low orbit about the destination one. General plots linking together the travel time, the specific mass of the generator and the propellant consumption are obtained.