Shape
The inlet cone is shaped so that the shock wave that forms on its apex is directed to the lip of the intake; this allows the engine to operate properly in supersonic flight. As speed increases, the shock wave becomes increasingly more oblique (the cone gets narrower). As a result, some inlet cones (for example, on the SR-71) are designed to move axially to maintain the shock-on-lip and allow efficient operation over a wider range of flight speeds. On MiG-21 this movement also makes the opening between the intake (diffusor) lip and the cone smaller, preventing the inside of the intake section from bursting open from dynamic air overpressure at the aircraft's highest speeds above Mach 2.
Read more about this topic: Inlet Cone
Famous quotes containing the word shape:
“Art, like Nature, has her monsters, things of bestial shape and with hideous voices.”
—Oscar Wilde (1854–1900)
““Must a name mean something?” Alice asked doubtfully.
“Of course it must,” Humpty Dumpty said with a short laugh: “my name means the shape I am—and a good handsome shape it is, too. With a name like yours, you might be any shape, almost.””
—Lewis Carroll [Charles Lutwidge Dodgson] (1832–1898)
“Political image is like mixing cement. When it’s wet, you can move it around and shape it, but at some point it hardens and there’s almost nothing you can do to reshape it.”
—Walter F. Mondale (b. 1928)