SCRAMJET ENGINE

Scramjet engine is more prominent and successful then ramjet engines. With increase in temperature and pressure how scramjet engine beats ramjet in technology and speed all of these things are discussed below.

Need of Scramjet Engine

When the speed of a ramjet increases above Mach 5 then the temperature in the combustion chambers can exceed 2000 °C. So at this temperature the air is so hot that not much additional energy can be gained by burning fuel. There can also cause some serious material damage to the inside of the engine.

Scramjet engine is a way to overcome this speed limitation. In a scramjet engine (supersonic combustion ramjets) the incoming air is not slowed down to subsonic speeds and it is burned at supersonic speed. But this creates other problems. The biggest of these problems is getting the fuel to mix efficiently with the air and burn in milliseconds or less before that and because of this it exits the nozzle. It has been practically proved that hydrogen gas can be made to mix efficiently and burn under these conditions.

Airframes need to be extremely good aerodynamic to minimize temperature increases resulting from the friction they experience when slamming into air at such high speeds due to rub with air. The frictional energy from any colliding air is transferred to the airframe and because of this temperatures can get enough high to destroy the aircraft. The diagram given above shows how the nose of NASA’s X–43A is designed to slice through the air and eliminates as much drag as possible.

Also like in any regular ramjets the scramjet must be accelerated to an operational velocity around Mach 5. So one way to do this is to use a rocket as shown on the model shown above. On November 16, 2004, NASA successfully flew the X–43A at Mach 9.6 by first having a B–52 carry the first stage of a Pegasus rocket with an X–43A attached (see inside the circle, on the photograph above) to an altitude of 40,000 feet. At that point the Pegasus was dropped and ignited. It carried the X–43A to an altitude of around 110,000 feet where the rocket released the X–43A to fire its own scramjet engine.
At present much more research needs to be done on hypersonic flight, where it is predicted that scramjet engine may someday reach speeds between Mach 10 and 25.