This diagram shows just how the action of the two nozzles is able to help provide so
much thrust at Mach 2. The 'cooling air' from the engine bay into the nozzle annulus s the secondary airflow that was diverted the intake ramps, and this gives the high pressure efflux an aerodynamic cushion to expand against from within the divergent secondary nozzle buckets. This gives a dramatic reduction in the thrust that would otherwise be wasted due to the high pressure efflux over-expanding/flaring against the very low static air pressure.
Dude 
Last edited by M2dude; 10th Sep 2010 at 08:33.