Conceptual design of two-stage reusable launch systems using X-33

A conceptual design of a rocket-based two-stage partially reusable launch system is first explored. For the first stage, the X-33 experimental hypersonic vehicle is assumed as a realistic candidate of a rocket-based vehicle. The second stage is assumed to be expendable, which inserts 1-ton payload into low Earth orbit. Although several optimistic assumptions are made, we have found three sets of solutions for various orbital inclination angles. The payload to takeoff weight ratio of the resulting partially reusable launch system is found to be about 0.7%. In addition, a rocket-based two-stage fully reusable system is also explored by assuming the X-33 as the second stage and the VentureStar as the first stage. A payload of 6 ton into LEO is found possible. The payload to takeoff weight ratio for this configuration becomes slightly better than 0.5%.