Technology and staging effects on two-stage-to-orbit systems

Horizontal takeoff and landing two-stage systems with an airbreathing first stage and rocket second stage are evaluated for staging Mach numbers that range from 5 to 14. All systems are evaluated with advanced technologies being developed in the NASP Program and sized to the same mission requirements. With these advanced technologies, the two-stage systems are heavier than the single stage. The weights of the two-stage systems are closely related to staging. Using a rocket on the first stage to accelerate from the turboramjet limit of Mach 6 to Mach 10 signiificantly decreases dry weight as compared to the Mach 6-staged system. The optimum dry weight staging Mach number for the scramjet two-stage system is Mach 12. At a 40 percent weight growth (current technology level), the scramjet two-stage systems are half the weight and less sensitive to weight changes than the single stage, but still require substantial technology development in the areas of inlets, nozzles, ramjet propulsion, active cooling, and high-temperature structures.