The National Aerospace Plane: Cost Considerations for the Follow-on Vehicle
The United States and other countries have been pursuing the development of hypersonic technologies and experimental vehicles to demonstrate technical feasibility of aircraft-like operations for future space launch vehicles. Ultimately, the usefulness of these vehicles will depend as much on their economics as on their operational utility. If they are relatively cheap, they will find a number of roles and missions, but if they are expensive, they will have a hard time finding a niche. This paper examines one of the critical cost aspects of a U.S. National Aerospace Plane (NASP) derived vehicle (NDV) program--the acquisition cost of a fleet of single-stage-to-orbit (SSTO) vehicles. The paper places the vehicle acquisition costs within the context of future U.S. space launch demand. It deals with the uncertainty of the cost-estimative relationships for NASP-type experimental technologies required to perform a SSTO space launch mission--high performance materials, multimode propulsion systems, and sophisticated avionics. A sensitivity analysis is used to portray the impact of launch costs (dollars per pound in orbit) of a number of operational considerations, notably, total number of flights per vehicle, launch demand, fleet size, research, development, testing, and evaluation (RDT&E) cost, uncertainty in cost estimating relationships (CER), and investment cost. The NDV launch costs are compared with current U.S. launch costs that are based on the use of expendable launch vehicles and the shuttle. This analysis concludes that it is highly unlikely that U.S. space launch costs will decrease dramatically by the development of a single-stage-to-orbit, fully reusable NASP-derived vehicle. This conclusion was reached without considering operating and service costs, which would only increase the launch costs even more.