  A highly reflective sail provides a way to propel a spacecraft out of the
solar system using solar radiation pressure. The closer the spacecraft is to
the Sun when it starts its outward journey, the larger the radiation pressure
and so the larger the final velocity. For a spacecraft starting on the Earth's
orbit, closer proximity can be achieved via a retrograde impulse from a rocket
engine. The sail is then deployed at the closest approach to the Sun. Employing
the so-called Oberth effect, a second, prograde, impulse at closest approach
will raise the final velocity further. Here I investigate how a fixed total
impulse ({\Delta}v) can best be distributed in this procedure to maximize the
sail's velocity at infinity. Once {\Delta}v exceeds a threshold that depends on
the lightness number of the sail (a measure of its sun-induced acceleration),
the best strategy is to use all of the {\Delta}v in the retrograde impulse to
dive as close as possible to the Sun. Below the threshold the best strategy is
to use all of the {\Delta}v in the prograde impulse and thus not to dive at
all. Although larger velocities can be achieved with multi-stage impulsive
transfers, this study shows some interesting and perhaps counter-intuitive
consequences of combining impulses with solar sails.
