  This paper presents a methodology for the concurrent first-stage preliminary
design and ascent trajectory optimization, with application to a Vega-derived
Light Launch Vehicle. The reuse as first stage of an existing upper-stage
(Zefiro 40) requires a propellant grain geometry redesign, in order to account
for the mutated operating conditions. An optimization code based on the
parallel running of several Differential Evolution algorithms is used to find
the optimal internal pressure law during Z40 operation, together with the
optimal thrust direction and other relevant flight parameters of the entire
ascent trajectory. Payload injected into a target orbit is maximized, while
respecting multiple design constraints, either involving the alone solid rocket
motor or dependent on the actual flight trajectory. Numerical results for SSO
injection are presented.
