----- Original Message ----- From: "Firat Barlas" <firat@macrolimit.com> Sent: Wednesday, September 03, 2003 2:39 PM Subject: Re: Progress R/B decay also seen from Crete? > > I have a question : Have anybody heared sound of a reentry? (except > shuttle) I hear 3 or 4 boom sound 7 or 8 minutes after reentry. > > If we think that velocity of the sound = 300 m/sec (because of low density > in upper atmosphere) > between 420 - 480 seconds > Distance = 126 - 144 kms > > That's a very realistic result. (100 kms altimeter at 30 degrees elevation) With normal meteoric fireballs, sonic booms are produced when fireballs penetrate deeply into the atmosphere to altitudes below 50 km. As a decaying rocket enters the atmosphere at much less velocity than the even the slowest meteoroid (but on the other hand, has a larger diameter), I am not sure what differences there might be between a rocket decay and a meteoroid. But while a distance of 100 km measured horizontally for a typical larger meteoroid would not seem problematic to me (the sonic boom of the large Taurid meteoric fireball of 17 november 1995, where the sonic boom was recorded on the audio tracks of the meteor video camera's at two of our stations, was at a similar distance. If produced during the major breakup of this fireball, it originated at approximately 40 km atmospheric altitude), a sonic boom from an atmospheric altitude of 100 km is perhaps a bit less likely. So the observation of sonic booms would suggest a deep penetration of remains of the decaying rocket to altitudes less than 50 km. A sky elevation of 30 degrees for the point of origin as seen from the point of arrival (and ignoring earth curvature in this rough calculation) and sound travel distance about 125 km (7 minutes travel time) from point of origin to receiver, would suggest about 60 km atmospheric altitude for the origin of the sonic boom. Would the sky elevation be 25 degrees instead of 30, this would already bring it down to 50 km atmospheric altitude, which is in the reasonable realm for sonic booms. And anyhow this are rough approximations only. But it might indeed suggest that the body survived to 50 km or less. This would need the decay trajectory to come to within 125 km of your location of course. - Marco ------ Marco Langbroek Leiden, the Netherlands 52.15896 N, 4.48884 E (WGS 84) meteorites@dmsweb.org http://home.wanadoo.nl/marco.langbroek ------ ----------------------------------------------------------------- To unsubscribe from SeeSat-L, send a message with 'unsubscribe' in the SUBJECT to SeeSat-L-request@satobs.org List archived at http://www.satobs.org/seesat/seesatindex.html
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