Page content and layout © 1996-2001 Michael Grabois and Astra Enterprises.Last updated: Feb. 15, 2001
Compilation copyright © 1997-2001 by Michael R. Grabois. This document may be freely redistributed in various electronic media (including, but not limited to, e-mail, Usenet, and the World Wide Web) in its complete and unmodified form. It may not be reproduced for profit in commercial outlets (such as, but not limited to, CD-ROMs and books) without prior written consent from the author. Other use requires written permission of the author. Except as where noted in the individual answer, all material was written by the compiler of this document. Standard disclaimer: this is in no way officially endorsed by NASA or any of its contractor companies.
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Here's a bit from the Dryden Flight Research Center, at Edwards Air Force Base in California:
Sonic booms are created by air pressure. Much like a boat pushes up a bow wave as it travels through the water, a vehicle pushes air molecules aside in such a way they are compressed to the point where shock waves are formed.
These shock waves form two cones, at the nose as well as at the tail of the vehicle. The shock waves move outward and rearward in all directions and usually extend to the ground. As the shock cones spread across the landscape along the flightpath, they create a continuous sonic boom along the full width of the cone's base. The sharp release of pressure, after the buildup by the shock wave, is heard as the sonic boom.
The nose and tail shock waves are usually of similar strength. The time interval between the nose and tail shock waves is primarily dependent on the size of the aircraft and its altitude. Most people on the ground cannot distinguish between the two and they are usually heard as a single sonic boom. As the time interval increases, two booms are heard. A small fighter-type aircraft about 50 ft long will generate nose and tail shock waves of less than a tenth of a second (0.1 sec). The ear usually detects these as a single sonic boom.
The interval between nose and tail shock waves on the Space Shuttles, which are 122 ft long, is about one-half of a second (0.50 sec), making the double boom very distinguishable.
For more info, go to:
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[with inputs from Todd L. Sherman]
The good news is that there will be a "sightings" notation for the shuttle as it makes its way to the landing site after deorbiting. The shuttle looks spectacular as it streaks across the sky in a fireball. A day or so before the landing, the sighting opportunities will be listed on the NASA Shuttle Web:
This list will list many cities along the incoming flight path and offers appearance and disappearance azimuths, maximum heights, approximate times post-max-alt that the sonic boom should be heard, etc.
The bad news is that if they wave off an orbit, there may not be a "one rev delay" sightings list.
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Please submit all corrections, additions, and suggestions to WizardImps@hotmail.com.
Page content and layout © 1996-2001 Michael Grabois and Astra Enterprises.
Last updated: Feb. 15, 2001