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Old Sep 11, 2009, 08:48 PM
Embrace the suck
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Welcome home Discovery

Nice thump!

Nauga,
patron of the arts
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Old Sep 11, 2009, 09:08 PM
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Felt like it was about to land on the house!! Apparently the flight path brought it over Santa Monica, two miles away...
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Old Sep 11, 2009, 09:13 PM
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Why do these things always have two sonic booms?
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Old Sep 11, 2009, 09:15 PM
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Didnt hear anything here in Oceanside, I was even out side waiting drinking a brew

Two sonic booms????? Even the sonic boom has a boom
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Old Sep 11, 2009, 09:15 PM
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Quote:
Originally Posted by c.walker
Why do these things always have two sonic booms?
I don't know, but I'll bet Nauga does...
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Old Sep 11, 2009, 09:17 PM
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http://www.pbs.org/wgbh/nova/barrier/boom/choice4.html

According to this site, it's because the nose and tail shock waves each create their own boom.
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Old Sep 11, 2009, 09:21 PM
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I believe one is from the nose and one from the tail, but don't know the details.

Edit: too slow once again

Bummer I missed it, I normally try and watch it on NASA Tv.
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Old Sep 11, 2009, 09:23 PM
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Quote:
Originally Posted by c.walker
Why do these things always have two sonic booms?
What we hear as a 'boom' is really a large pressure change in a small area passing over us. One of pressure changes forms at the nose of the shuttle (or anything supersonic), one forms at the tail. BoomBoom as both waves pass over you. These pressure changes form shock cones around the nose and tail so the pressure field trails behind the shuttle - that's why you hear the boom *after* the shuttle passes overhead.

There are really more than just two but usually two strong ones. You can sometimes see them as condensation clouds when conditions are right. edit: not to be confused with condensation clouds that also form subsonically at high lift.

Much like music, they're more fun to make than to listen to

Nauga,
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Old Sep 11, 2009, 09:39 PM
Not so fast....
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When I lived in the UK, I used to have my holidays near the Bristol channel. That is where the Concorde flight to NY would light the afterburners and go transonic. So you would hear Concorde going transonic in the morning, and then returning later in the afternoon. Both times, two deep thumps. You could set your watch by it.
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Old Sep 11, 2009, 09:52 PM
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Quote:
Originally Posted by nauga
What we hear as a 'boom' is really a large pressure change in a small area passing over us. One of pressure changes forms at the nose of the shuttle (or anything supersonic), one forms at the tail. BoomBoom as both waves pass over you. These pressure changes form shock cones around the nose and tail so the pressure field trails behind the shuttle - that's why you hear the boom *after* the shuttle passes overhead.

There are really more than just two but usually two strong ones. You can sometimes see them as condensation clouds when conditions are right. edit: not to be confused with condensation clouds that also form subsonically at high lift.

Much like music, they're more fun to make than to listen to

Nauga,
shocked
Neat! Somehow I had fixed on the idea that the first compression layer excluded subsequent ones. Guess not.

Here's a few pretty pictures:

T38 (middle of the page)
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Old Sep 11, 2009, 10:08 PM
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Quote:
Originally Posted by c.walker
Here's a few pretty pictures:
[Spiccoli/]Hey, I know those dudes [/Spiccoli]

One of the cool things about shock pictures is you can estimate the Mach no. by the angle of the shocks before they coalesce. The faster the speed (really higher the Mach no.), the tighter the shock cone.

Nauga,
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Old Sep 12, 2009, 04:33 AM
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Wirral, (UK)
Joined Dec 2003
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Quote:
Originally Posted by nauga
[Spiccoli/]Hey, I know those dudes [/Spiccoli]

One of the cool things about shock pictures is you can estimate the Mach no. by the angle of the shocks before they coalesce. The faster the speed (really higher the Mach no.), the tighter the shock cone.

Nauga,
and his hedgehog
Maybe about Mach 0.95? Shock almost at 90 to the nose!

Supersonic = 2 shocks but Subsonic-Transonic just one shockwave visible in all images but 2 booms heard.
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