Design Space Exploration of a Reusable Launch Vehicle Through Integrated Stage-Mission Optimization

This paper presents a design space exploration framework for a reusable launch vehicle (RLV) based on an integrated stage–mission optimization problem. In the early design phase, propulsion and structural parameters are not yet fixed, so it is important to understand how system performance varies over the design space spanned by these uncertain parameters. To address this, a reduced-order design space is defined using stage-correlated specific impulse and structural ratio as system-level design variables. At each sampled design point, a unified optimal control problem is solved to optimize payload mass, stage propellant masses, and ascent attitude profiles subject to mission, load-relief, gross lift-off weight, impact point, and reusability constraints, the latter modeled through a descent velocity increment requirement that reserves propellant for soft landing. A case study of a 500-ton-class, two-stage partially reusable launch vehicle performing a return-to-launch-site mission from a range-constrained site shows that structural efficiency is a dominant driver of payload performance, and that impact point constraints strongly influence ascent trajectory shape and velocity losses. These results indicate that the proposed framework is a practical tool for early phase RLV design space exploration.