Comments on: What does it mean exactly when a jet breaks the sound barrier?

By: Spitfire

Spitfire — Fri, 02 Oct 2009 21:20:59 +0000

When a jet breaks the "sound barrier". it means that the jet has exceeded the speed at which sound tavals (roughly 760 MPH at sea level and as you increase your altitude, that speed goes down). the water vapor "ring" has somthing to do with the way that the aircraft is pushing aside the air andcreating this "cloud". but Im not really able to discribe it as I don totally understand it.

http://www.flickr.com/photos/doneastwest/163100543/
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By: rohak1212

rohak1212 — Fri, 02 Oct 2009 20:31:59 +0000

Breaking the sound just means flying faster than sound. Sound travels through the air at different speeds depending on air density. At Sea level it’s about 760mph, at 30,000 feet it’s about 660. That vapor cloud is caused by the shock wave that builds up when the aircraft is flying very near to the speed of sound, this shock wave result in a sharp reduction in air pressure, causing the water to condense, forming a cloud.
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By: Mark

Mark — Fri, 02 Oct 2009 20:08:59 +0000

There is no sound barrier. The "breaks the sound barrier" expression doesn’t mean anything. The speed of sound is not a barrier.

Water vapor is not visible. If you’re seeing water, it is not vapor.
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By: 1999 Nissan Skyline GTR Vspec

1999 Nissan Skyline GTR Vspec — Fri, 02 Oct 2009 19:42:59 +0000

when it is traveling faster than the speed of sound is when it breaks the sound barrier
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By: Mike

Mike — Fri, 02 Oct 2009 18:53:59 +0000

Breaking the sound barrier implies going faster than the speed of sound (roughly 343 m/s but changes with temperature). It is referred to as a barrier because early aircraft had difficulty flying near that speed because of shocks and certain effects associated with them. (See transonic section in ref below)

The water vapor forms in low-pressure, low-temperature regions in the flow. Looking at pictures, it seems like it occurs near the aft part of the vehicle, where the cross-section area is getting smaller. This would cause what is referred to as an expansion fan, this creates a "fan" of decreasing pressure and temperatures aways from the aircraft. If the pressure drops to the saturation pressure (pressure at which water boils), at the cooled temperature, a water-vapor mixture can form.
References :
http://aerodyn.org/
http://en.wikipedia.org/wiki/Prandtl-Meyer_expansion_fan

By: crewchief1949

crewchief1949 — Fri, 02 Oct 2009 18:43:59 +0000

breaking the sound barrier is when the vehicle exceeds the speed at which sound travels. The cone of vapor you see is the existing moisture in the air being condensed by pressure wave created by the vehicle creating a cloud.
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By: james

james — Fri, 02 Oct 2009 18:29:59 +0000

When a plane or car breaks the sound barrier it means it is going faster than the speed of sound ( roughly 1000 miles per hour).
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By: Shaun

Shaun — Fri, 02 Oct 2009 17:51:59 +0000

the sound barrier usually refers to flight at transonic speeds, between subsonic and supersonic speeds. The term came into use during World War II when a number of aircraft started to encounter the effects of compressibility, a grab-bag of unrelated aerodynamic effects. The term fell out of use in the 1950s when aircraft started to routinely "break" the sound barrier. Refer to the speed of sound for the science behind the velocity referred to as the sound barrier.
References :
I am an aircraft mechanic

By: Corey M

Corey M — Fri, 02 Oct 2009 17:12:59 +0000

the sound barrier is a point in speed when an object is travelling faster than the speed of sound of 761.2 MPH (mach 1) at sea level. It is a shockwave (actually 2 shockwaves, one at the nose and one at the tail) that the jet creates when accellerating to or decelerating from the speed of sound. All planes that can fly faster than the speed of sound create two "sonic booms" (the name for the sound you hear as a result of the plane breaking the sound barrier) but are heard as one because the distances (just a few 10’s of meters) are so close together… The only exception, that i know of is the Space Shuttle orbiter (which is not really a plane anyway). Because of it’s large size, the two sonic booms occur a half second apart and are distinctly heard one after the other.

Now as to the vapor that is formed, I believe that it is just vapor from the engines mixed with cold air that makes a ring around the jet when it does break the sound barrier.
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By: londoner

londoner — Fri, 02 Oct 2009 17:04:59 +0000

sound travels with speed of 342.00 meter/sec.when a jet gets over this speed then the sound barrier is broken.At this
point there will be a shock-wave going 360 degrees around
the object and this wave hits the Airs atoms and usually makes a huge noise.The size of this noise could be measured depending on "size of force of engine "at the time
of breaking point.Russian made "sukho" jet-fighters break the barrier with a density of 3000.HP/MIL2.american made jets
from "phantoms" to newer jets can break the barrier faster than "sukhos".French mirrage jets can break the barrier in 5-6 seconds
References :
my source :a close relative is a fighter-jet pilot