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 2012-10-15, 22:32 #1 davieddy     "Lucan" Dec 2006 England 2×3×13×83 Posts Did that guy actually break the the sound barrier? What was the speed of sound where he reached 800+ mph? David
2012-10-15, 23:23   #2
Batalov

"Serge"
Mar 2008
Phi(4,2^7658614+1)/2

100011101001002 Posts

A question of this depth can be only matched by Svejk's riddle.

Quote:
 Originally Posted by The Good Soldier Svejk "Would you know how to calculate the diameter of the globe?" "No, I'm afraid I wouldn't," answered Svejk, "but I'd like to ask you a riddle myself, gentlemen. Take a three-storied house, with eight windows on each floor. On the roof there are two dormer windows and two chimneys. On every floor there are two tenants. And now, tell me, gentlemen, in which year the house-porter's grandmother died?"

2012-10-15, 23:28   #3
Dubslow

"Bunslow the Bold"
Jun 2011
40<A<43 -89<O<-88

3×29×83 Posts

http://en.wikipedia.org/wiki/Red_Bull_Stratos#Analysis
Quote:
 The FAI announced that confirmation of exact times and altitudes could take several weeks. The data will be evaluated first by the Austrian Aeroclub (ÖAeC) since Baumgartner is an Austrian citizen and will then be confirmed by the FAI. While the reported values may change on verification, there was no doubt that Baumgartner broke the sound barrier.

 2012-10-16, 00:52 #4 davieddy     "Lucan" Dec 2006 England 2·3·13·83 Posts I didn't hear the sonic boom, but I am going mildly deaf. D
2012-10-16, 00:58   #5
davieddy

"Lucan"
Dec 2006
England

2×3×13×83 Posts

Quote:
 Originally Posted by Batalov A question of this depth...
As an ex physics teacher I should be able to remember a formula for the speed of sound

 2012-10-16, 01:03 #6 ewmayer ∂2ω=0     Sep 2002 República de California 263768 Posts c = sqrt(gamma*R*T) for quasi-ideal gases. For air, adiabatic index (= ratio of specific heats c_p/c_v) gamma = 1.4, to a very close approximation. R is the universal gas constant normalized by the molar mass of the gas (or gas mixture) in question. Since gamma and R are independent of local atmospheric conditions, if you know c at some standard conditions just use the variation as sqrt(T) to compute elsewhere. Colder = lower speed of sound. Last fiddled with by ewmayer on 2012-10-16 at 01:12
2012-10-16, 07:36   #7
davieddy

"Lucan"
Dec 2006
England

2×3×13×83 Posts

Quote:
 Originally Posted by ewmayer c = sqrt(gamma*R*T) for quasi-ideal gases. For air, adiabatic index (= ratio of specific heats c_p/c_v) gamma = 1.4, to a very close approximation. R is the universal gas constant normalized by the molar mass of the gas (or gas mixture) in question. Since gamma and R are independent of local atmospheric conditions, if you know c at some standard conditions just use the variation as sqrt(T) to compute elsewhere. Colder = lower speed of sound.
10/10 so far.

Now speaking as a non-specialist atmospherical physicist, what was T?

D

 2012-10-16, 15:10 #8 garo     Aug 2002 Termonfeckin, IE 5·19·29 Posts http://en.wikipedia.org/wiki/Speed_of_sound In particular look at this graph on that page: http://en.wikipedia.org/w/index.php?...962.svg&page=1
 2012-10-16, 21:58 #9 c10ck3r     Aug 2010 Kansas 547 Posts I believe he did indeed break the sound barrier. Fear not, however, the world's best scientists are carefully reconstructing it, and will hopefully finish the repairs by December :)
 2012-10-17, 00:03 #10 ewmayer ∂2ω=0     Sep 2002 República de California 2×13×443 Posts Proposal: "The Human Meteorite" Competition Next up: Starting with a spacewalk from orbit (any height, it must just be high enough that the original orbit is not rapidly decaying itself) and without the use of any artificial thrusters aside from maneuvering thrusters having a maximum total impulse of (say) 100 Newton-seconds, perform a capsule-less re-entry and descent from space, landing safely on earth. By "capsule-less" let us say wearing a total amount of gear -- including spacesuit, drag chutes and/or gliding apparatus -- of total mass no greater than that of its human wearer. (I honestly believe some daring soul will accomplish this before the century is out). The physics of such a re-entry are quite interesting. There are at least 2 or 3 distinct strategies one might employ. Discuss!
2012-10-17, 00:38   #11
Uncwilly
6809 > 6502

"""""""""""""""""""
Aug 2003
101×103 Posts

2·4,297 Posts

Quote:
 Originally Posted by ewmayer The physics of such a re-entry are quite interesting. There are at least 2 or 3 distinct strategies one might employ. Discuss!
A ballute would be my guess.

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