🚀 go-pugleaf

About sonic booms--you guys must live in the wrong neighborhood :-)  Sonic
booms are quite common here at Dryden, since we're right under the medium-
altitude supersonic corridor.  Come visit us, for the public tour, and you'll
probably hear several.

The overpressure and other characteristics of the shock are functions of the
aircraft altitude, Mach, size, and weight.  If the aircraft is very high,
for example, the shock will have dissipated somewhat before it reaches the
ground and the boom will be more like a rumble.  The best booms are very 
sharp and distinct, with quite a bit of high-frequency content.  These come 
from relatively low, fast, close aircraft.  Double booms, like the
Shuttle produces, aren't that uncommon.  An F-4 can produce a very nice 
double boom--I've heard & seen them do it.  There's a clue in that statement,
that they were low enough and close enough that I could see them doing it.

Any aerodynamics text will show you the shock waves coming off an aircraft.
If you want to see pictures, look in Van Dyke's book, "An Album of Fluid
Motion."  He has a chapter of shock wave pictures and another of supersonic
flow.  This is an outstanding book, which everyone interested in aerodynamics
should have.

--

M F Shafer
NASA Ames-Dryden Flight Research Facility
shafer@elxsi.dfrf.nasa.gov or shafer@drynix.dfrf.nasa.gov

NASA management doesn't know what I'm doing and I don't know what they're
doing, and everybody's happy this way.