One thing has always been true about rockets: The farther and faster you want to go, the bigger you rocket needs to be. Why? Rockets combine a liquid fuel with liquid oxygen to create thrust. Take away the need for liquid oxygen and your spacecraft can be smaller or carry more pay load.That's the idea behind a different propulsion system called "scramjet," or Supersonic Combustion Ramjet The oxygen needed by the engine to combust is taken from the atmospheric air passing through the vehicle, instead of from a tank onboard Its mechanically simple as it has no moving parts. All this makes the craft smaller, lighter, faster and have more room to carry payload.
In a conventional ramjet, the incoming supersonic airflow is slowed to subsonic speeds by multiple shock waves, created by back-pressuring the engine. Fuel is added to the subsonic airflow, the mixture combusts, and exhaust gases accelerate through a narrow throat, or mechanical choke, to supersonic speeds. By contrast, the airflow in a pure scramjet remains supersonic throughout the combustion process and does not require a choking mechanism, which provides optimal performance over a wider operating range of Mach numbers. Modern scramjet engines can function as both a ramjet and scramjet and seamlessly make the transition between the two.
Download seminar docs :