IS BIGGER ALWAYS BETTER - AN ECONOMIC-STUDY OF UNITED-STATES ETO VEHICLE ARCHITECTURES

This analysis, performed as part of NASA's Space Transportation Infras tructure Study, compares the cost efficiency of two candidate launch v ehicle families, used in conjunction with existing expendable launch v ehicles and the Shuttle, to accomplish the nation's future space missi ons through 2030. Missions analyzed include those identified in NASA's Civil Needs Data Base (CNDB) and Space Exploration Initiative (SEI) O ption E program, as well as estimates of commercial and U.S. Departmen t of Defense flights. A family of Shuttle-derived In-line vehicles is compared against a family designed around a vehicle optimized for larg e (250 t) payloads. The analysis is performed within the context of an entire space transportation architecture. The goal is to determine wh ich architecture best captures the required missions most cost-effecti vely. Results indicate that, for the particular mission model analyzed , neither option is clearly superior across the entire payload range. The Shuttle-derived family displays a better evolutionary path for sup porting the total mission model (CNDB plus SEI missions). It also redu ces Earth-to-orbit (ETO) peak funding by 20%. The architecture incorpo rating the heavy lift ETO family minimizes SEI program cost and on-orb it operations but is subject to greater schedule risk because of the n eed for concurrent ETO core and engine development. Note that the U.S. Air Force's Advanced Launch System approach and philosophy is not inc luded in the trade study presented herein.