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22 August 2007


Dear Telstar Logistics:
As I was sitting on my ass listening to NASA's streamed play-by-play of the space shuttle Endeavour's return to terra farma, I heard a pair of booms as the vehicle descended and decelerated. Is such a phenomenon attributable to slowing past the speed of sound and passing back through said Prada-Glockenspiel vapor singularity, or is it just an Idaho thing. Long time listener, first time caller. I'll take my answer off the air.
Boffo in Boise


Thanks for tuning in. Sounds to us like a classic N-Wave situation. The Wikipedia explaineth why you heard those two booms (instead of just one):

In smooth flight, the shock wave starts at the nose of the aircraft and ends at the tail. There is a sudden rise in pressure at the nose, decreasing steadily to a negative pressure at the tail, where it suddenly returns to normal. This "overpressure profile" is known as the N-wave because of its shape. The "boom" is experienced when there is a sudden rise in pressure, so the N-wave causes two booms, one when the initial pressure rise from the nose hits, and another when the tail passes and the pressure suddenly returns to normal. This leads to a distinctive "double boom" from supersonic aircraft.

Apart from that, might we suggest searching your local Yellow Pages for a good proctologist? Thanks for your call and have a great commute.

Dear sirs,

I am just finishing writing a book about gravity and wish to use the image at the top of the page as an illustration in the book. can you please send me contact details about the owner of the image so that I might contact them with a view to using the image. Or, please contact them and ask them to make contact with me.

I thank you in anticipation of a prompt reply.

Chris Coles.

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