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FIGURE D.2 Quality function deployment rankings for TA01 Launch Propulsion Systems.

large benefit to NASA and because they are a good match with NASA’s mission and expertise. In fact, the current state of the art in TBCC and RBCC technology has benefited from past research supported by NASA’s aeronautics research and technology program.

The International Space Station is not an appropriate test bed for any launch propulsion technologies.

Technology 1.3.2, Rocket Based Combined Cycle

Rocket Based Combined Cycle (RBCC) propulsion systems combine the high specific impulse of air breathing ramjet and scramjet engines with the high thrust-to-weight ratio of a chemical rocket. They promise to deliver launch systems with much lower costs than present launch systems. A vehicle using an RBCC propels itself from the ground using a rocket with secondary air to increase its thrust (ejector ramjet). At high enough Mach numbers (M ~ 3) for ramjet operation, the rockets turn off and air breathing propulsion is used. The ramjet mode transitions to scramjet mode at even higher Mach numbers. After the altitude is high enough to make scramjet operation impractical due to lack of oxygen, the vehicle reverts to a pure rocket mode. This type of propulsion system usually has a single flow path for the entire operating range. RBCC system components are at TRL 3 to 4.

NASA has been investigating rocket-air breathing cycles for many years and has been at the helm of experimental and numerical studies. The experimental X-43 program exemplifies NASA’s commitment to and expertise in hypersonic air breathing cycles. There is also considerable Air Force expertise in air breathing hypersonic flight as demonstrated by the recent X-51 flight of a hydrocarbon scramjet. Based on the common need within NASA



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