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Old 25th Jun 2009, 19:39
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johndoe42
 
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Theoretically, ignoring for example drag on the airframe and internal engine parts, you can fly a small bit faster than the exhaust velocity, due to the added mass of the burnt fuel. How much depends on the ratio of air and fuel masses. At some point the deceleration of the air mass and the acceleration of the fuel reach an equilibrium, and you don't accelerate any further.

At the extreme of this air/fuel ratio, when reducing the air intake down to zero, you get a rocket engine. Rocket engines can accelerate to virtually any speed (if the fuel wouldn't run out at some point), irrespective of the exhaust velocity.

The underlying physical principle is the law of conservation of impulse. Newton's second law, as outlined above, only follows from that.

In reality however, with all the various drag forces acting on the aircraft, and with the small amount of fuel compared with the air mass, you will always fly a fair bit slower than the exhaust velocity.
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