text: If the supersonic’airstream can be captured, 
  the shock wave formations tiill be swallowed 
  and a gradual contraction will reduce the speed 
  to just above sonic. Subsequent diverging flow 1 
  section can then produce the normal shock 
  wave which slows the airstream to subsonic. 
  Further expansion continues to slow the air to 
  lower subsonic speeds. This is the convergent- 
  divergent type inlet shown in figure 3.20. 
  If 
  the initial contraction is too extreme for the 
  inlet Mach number, the shock wave formation 
  will not be swallowed and will move out in 
  front of the inlet. The external location of the 
  normal shock wave will produce subsonic flow 
  immediately at the inlet. Since the airstream 
  is suddenly slowed to subsonic through 
  the 
  strong normal shock a greater loss of airstream 
  energy wiIl occur. 
  
  SUPERSONIC ENGINE  INLETS. 
  
  Air 
  which enters the compressor section of a jet 
  engine or the combustion chamber of a ramlet 
  usually must be slowed to subsonic velocity. 
  This process must be accomplished with 
  the 
  least possible waste of energy. At flight speeds 
  Another form of diffuser employs an external 
  oblique shock wave which slows the super- 
  sonic airstream before the normal shock occurs. 
  the supersonic airstream could be 
  Ideally, 