Launcher Performance with Reserves

Abstract

The success probability of a space launch is guaranteed by propellant reserves. The upper-stage reserve represents a direct performance penalty because it reduces the maximum payload mass that can be injected on orbit by the launcher. The usual process consists of successively optimizing the trajectory for nominal conditions, and then assessing the necessary reserves to face the flight uncertainties. This process may yield large reserves when the trajectory is sensitive to the upper-stage features. A simple method is proposed to account for the upper-stage reserve directly within the trajectory optimization process. It results in a less sensitive nominal trajectory and, finally, a better guaranteed performance of the launcher. The method is illustrated on a classical launch trajectory optimization.