Comparison of Return to Launch Site Options for a Reusable Booster Stage

Abstract

There is a major need in the U.S. Air Force to develop launch vehicles that can be used for Operational Responsive Spacelift and possibly be used for rapid global Strike. One strategy to achieve these mission goals is to develop a Reusable Military Launch System (RMLS) or a hybrid system which uses a reusable booster with expendable upper stages. In support of the development work of the Aerospace Systems Design Branch (ASC/ENMD) of the USAF Aeronautical Systems Center at Wright-Patterson AFB, this study looked at comparing three basic methods for Return to Launch Site (RTLS) for a reusable booster. These methods are glideback to launch site, flyback using an airbreathing turbofan, and boostback using the booster's main or secondary rocket engines. The booster carries the upper stage(s) on its back to the staging point. Currently, most RTLS vehicle studies either assume a glideback or flyback booster. Very little work outside of the Kistler K-1 has been done to look at boostback methods. The vehicle modeling was integrated into ModelCenter using the MDO method of Optimizer Based Decomposition to handle the branching trajectory problem that arises from the booster performing a RTLS maneuver. Each of the three vehicles was optimized to minimize dry weight and gross weight separately in order to get a better understanding if boostback can provide any advantages over the two more traditional RTLS methods.