The Transonic Area Rule
The pressure drag of a generic slender body differs from that of the equivalent body
of revolution, from which the drag is minimal. This difference is identically zero if
the slender body has an axi-symmetric or cylindrical rear end. Both conditions can in
fact be satisfied by missiles and fast aircraft.
The equivalent body of revolution theory implies that the drag is also at a minimum
when the slender body has a smooth cross-area distribution (Whitcomb, 1956). This
idea was tested in the 1950s at NASA with various configurations having smooth and
indented bodies.
Figure 1: Crosswise area distribution of transonic aircraft
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