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. 
Another form of diffuser employs an external 
oblique shock wave which slows the super- 
sonic airstream before the normal shock occurs. 
Ideally, the supersonic airstream could be 
Revised January 1965 
238