A Multidisciplinary Performance Analysis of a Lifting-Body Single-Stage-to-Orbit Vehicle

Lockheed Martin Skunk Works (LMSW) is currently developing a single-stage-to-orbit reusable launch vehi- cle called VentureStar™. A team at NASA Langley Re- search Center participated with LMSW in the screening and evaluation of a number of early VentureStar™ con- figurations. The performance analyses that supported these initial studies were conducted to assess the effect of a lifting body shape, linear aerospike engine and me- tallic thermal protection system (TPS) on the weight and performance of the vehicle. These performance studies were performed in a multidisciplinary fashion that indi- rectly linked the trajectory optimization with weight es- timation and aerothermal analysis tools. This approach was necessary to develop optimized ascent and entry tra- jectories that met all vehicle design constraints. Significant improvements in ascent performance were achieved when the vehicle flew a lifting trajectory and varied the engine mixture ratio during flight. Also, a considerable reduction in empty weight was possible by adjusting the total oxidizer-to-fuel and liftoff thrust-to- weight ratios. However, the optimal ascent flight profile had to be altered to ensure that the vehicle could be trimmed in pitch using only the flow diverting capability of the aerospike engine. Likewise, the optimal entry tra- jectory had to be tailored to meet TPS heating rate and transition constraints while satisfying a crossrange re- quirement.