The market of small satellites has experienced substantial growth in the last decade due to the high level of miniaturization in its components, allowing missions that only a decade ago were the exclusive domain of much larger satellites. This tendency has opened a new field for the development of low cost small/micro launchers (Light Launcher Vehicles - LLVs) to act on this speciffc market, mostly private-led initiatives, called nowadays as NewSpace Launch Systems. This new approach has the advantage to fulfill with high quality the mission requirements, once these launchers are dedicated to LEO missions of small, micro, and nano satellites. In the design of launchers, the use of optimization methods to maximize the payload mass and the propellant storability, as well as minimize the structural mass for a given mission or range of missions is mandatory. During the optimization process, a method to maximize the overall vehicle performance, in general, expressed by the payload capability, is handling a combination of different propulsion systems to form the vehicle stages in association with an optimum trajectory analysis. Sometimes, manipulation of the propulsion system characteristics is also required, which results in modiffcations in the original motor design. In this work, the focus will be put on the Solid Rocket Motor (SRM) S-50, baseline of the current analyzes. The S-50 is under development to compose the first and second stages of the Brazilian Micro-satellite Launch Vehicle (VLM), and the first stage of the Suborbital Rocket VS-50. This SRM burns 12 tons of solid propellant during 80 seconds, and uses a composite (CFRP) motor case presenting an attractive structural ratio. This paper addresses the stage optimization problem by using gradient method algorithm to calculate the second and third optimal stages for certain mission considering the reference SRM S-50 as launcher first stage. In the procedures to find the optimum solution for the proposed problem, concepts of optimal trajectory, maximum payload capability, structure optimization, and properly ight dynamics and control analysis are applied. The methodology developed here will be applied on reference missions for consistency checking, and the preliminary design achieved is checked by a trajectory optimization software.