Orbit insertion at Saturn requires a large impulsive manoeuver due to the
velocity difference between the spacecraft and the planet. This paper presents
a strategy to reduce dramatically the hyperbolic excess speed at Saturn by
means of deep-space electric propulsion. The interplanetary trajectory includes
a gravity assist at Jupiter, combined with low-thrust maneuvers. The thrust arc
from Earth to Jupiter lowers the launch energy requirement, while an ad hoc
steering law applied after the Jupiter flyby reduces the hyperbolic excess
speed upon arrival at Saturn. This lowers the orbit insertion impulse to the
point where capture is possible even with a gravity assist with Titan. The
control-law algorithm, the benefits to the mass budget and the main
technological aspects are presented and discussed. The simple steering law is
compared with a trajectory optimizer to evaluate the quality of the results and
possibilities for improvement
