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Palomar

Member

From: USA

Registered: 2002-05-30

Posts: 9,734

Re: Sonic Boom *Seen*??

http://antwrp.gsfc.nasa.gov/apod/ap030504.html]Nope, not an April Fool's joke

*Is this for real?  And check out the "halo" over the rear of the cockpit.  :-\  Weird!

--Cindy

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We all know [i]those[/i] Venusians: Doing their hair in shock waves, smoking electrical coronas, wearing Van Allen belts and resting their tiny elbows on a Geiger counter...

--John Sladek (The New Apocrypha)

Mad Grad Student

Member

From: Phoenix, Arizona, North Americ

Registered: 2003-11-09

Posts: 498

Website

Re: Sonic Boom *Seen*??

Yep, that's a cool pic, isn't it. :;):

What you see is absolutely real. Of course, you can't exactly see a sonic boom, any more than you can see the wind, but the clouds form right where the pressure wave of the sonic boom is happening. It's a bit like the water vapor you see coming off dry ice, you can't actually see the carbon dioxide per say, but you can see the water vapor that condenses into teeny droplets wherever the supercold CO2 goes. The cloud serves as a tracer of sorts for the pressure wave. Wild stuff.

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A mind is like a parachute- it works best when open.

Palomar

Member

From: USA

Registered: 2002-05-30

Posts: 9,734

Re: Sonic Boom *Seen*??

*Hi MGS:  Yep.  Seems the cloud is likely perfectly round, but of course from the camera's angled vantage-point it looks egg-shaped. 

But what could explain that bit of arc-shaped cloud up over the rear of the cockpit?  I mean, why would it be *there*...and why a trace of additional cloud anyway *and* separate from the big cloud in back?

--Cindy

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We all know [i]those[/i] Venusians: Doing their hair in shock waves, smoking electrical coronas, wearing Van Allen belts and resting their tiny elbows on a Geiger counter...

--John Sladek (The New Apocrypha)

Dook

Banned

From: USA

Registered: 2004-01-09

Posts: 1,409

Re: Sonic Boom *Seen*??

A video of an F-14 doing a supersonic flyby and a huge Prandtl-Glauert condensation cloud forms. 

Download near the bottom of the article:
http://www.galleryoffluidmechanics.com/ … pegf14.htm

Mad Grad Student

Member

From: Phoenix, Arizona, North Americ

Registered: 2003-11-09

Posts: 498

Website

Re: Sonic Boom *Seen*??

I think the reason why there's a seperate cloud around the cockpit is due to the fact that the plane really isn't making one sonic boom as it passes mach 1. Different parts of the plane all have subtle aerodynamic nuance to them, and generally the different parts of an aircraft will all pass the sound barrier at slightly different times in different ways. There's a great picutre in my physics textbook that shows an F-111 breaking the sound barrier that was taken with a special camera that allows you to see the pressure waves on the airplane. Rather than one clean v-shaped wave steming from the nose to the tail there are about 20 or 30 teeny waves that all build on each other to create the sonic boom. The reason the cockpit in particular has its own condensation zone is likely because it sticks out farther than any other part of the plane near the nose. If the camera had taken the picture at a slightly different angle, you'd probably be able to see other clouds coming from the fuel tanks and hardpoints, but at the angle the pic was taken you can't really see them.

This reminds me of a story I remember my dad telling me a while ago. When he was in elementry school, growing up in southern Illinois, no regulations had been made yet on sonic booms over land. According to him, every week or so they'd be sitting there minding their own business (often in school) and suddenly hear an unbearibly noisy, window-rattling BOOM! Apparently he and his friends had good fun watching the teachers jump in utter fright with every sonic boom, and every once in a while they'd get one loud enough to crack a window. For course, for better or worse (almost definately better) those days are over now.

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A mind is like a parachute- it works best when open.

Palomar

Member

From: USA

Registered: 2002-05-30

Posts: 9,734

Re: Sonic Boom *Seen*??

The reason the cockpit in particular has its own condensation zone is likely because it sticks out farther than any other part of the plane near the nose. If the camera had taken the picture at a slightly different angle, you'd probably be able to see other clouds coming from the fuel tanks and hardpoints, but at the angle the pic was taken you can't really see them.

*Okay, thanks MGS.

I'd seen this photo perhaps 1-1/2 years ago, but it had no caption nor explanation of any sort with it.  I thought perhaps it was a sci-fi/fantasy illustration or perhaps even a model.

When I saw it at Astropix I knew it wasn't a "fake" anything. 

--Cindy

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We all know [i]those[/i] Venusians: Doing their hair in shock waves, smoking electrical coronas, wearing Van Allen belts and resting their tiny elbows on a Geiger counter...

--John Sladek (The New Apocrypha)