Optimization of electric propulsion systems considering specific power as function of specific impulse

The deployment of large electric power supplies in space in the near future allows the use of electric propulsion for transfer missions. In this paper the dependency of the specific power on the specific impulse has been taken into account. It shows that the optimal exhaust velocities are increased and the corresponding payload fractions decreased. To obtain a measure for the costs of missions, a transport rate is defined and included in the optimization. It further restricts the optimizable area and increases the specific impulse for high velocity increments. The comparison of different thruster types shows that not only the maximal thrust efficiency but also the form of eta sub(T)(c) is highly important for the results.