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Re: Cloud when breaking soundbarrier
Questions about the F-16

Thread Starter: s_ellebaut
Started: 08-28-2003 9:38 AM
Replies: 3

Community Server :: Forums » Military Aviation » Questions about the F-16 » Re: Cloud when breaking soundbarrier

s_ellebaut is not online. Last active: 8/1/2004 7:03:45 AM

s_ellebaut

Top 25 Posts

Joined on 08-13-2003
Posts 6

Cloud when breaking soundbarrier

I've seen a little movie where a jet breaks the soundbarrier, it creates a hughe cloud, what's the cause of this cloud forming? It's weird, you can even see the cloud bending when it's formed in front of the jet's nose just before the jet's inside the cloud. I've put the movie online: http://users.pandora.be/ellebaut/31tigersqn/soundbarrier.WMV

11 Mar 2005, 10:02 AM

KenV

Joined on 11-29-2004
Posts 27

Re: Cloud when breaking soundbarrier

This is a common occurance.

When flying transonic and low supersonic, the aircraft creates a powerful pressure wave (technically several waves, but one is predominant). It's like the bow wave a boat makes in the water. The area immediately behind the wave is a low presssure area. If the air is moist (high humidity) the moisture will condense in that low pressure area, which will appear as a "cloud". But notice that the "cloud" is moving with the aircraft which is moving at or above the speed of sound. That is impossible. What is happening is that the cloud is created in the low pressure area, the low pressure area moves forward, and the cloud dissappears. But a new cloud is instantly created in the new location of the low pressure area, and so on. So the cloud is not acutally moving with the aircraft, but instead a new cloud is created in each point in space as the aircraft moves through it.

Have you ever watched a space shuttle landing? You will see little cloud "streamers" come off the wing tips. The mechanism is completely different, but this is also a low pressure area where the moisture in the air condenses. The different mechanism causes the low pressure area to dissipate more slowly and so you see the cloud trail behind the shuttle a short distance.

Fighters doing heavy maneuvering in airshows also create transient clouds above their wings during high G maneuvers. A large area above the wing becomes a low pressure area and a "cloud" forms during the duration of the maneuver, usually only a second or less.

11 Dec 2005, 11:34 AM

vectorg is not online. Last active: 3/1/2006 12:47:50 AM

vectorg

Top 150 Posts

Joined on 12-11-2005
Posts 2

Re: Cloud when breaking soundbarrier

hi Ken,

A pilot friend told me once that when you see a vapor trail in the sky made by a passenger jet, the vapor comes from the jet engines. Is this always true? Can large vapor trails come from the wings or other parts of a high-flying plane? Thanks.

Gordon

12 Mar 2006, 3:48 AM

King_Wakka

Joined on 12 Mar 2006
Australia
Posts 16

Re: Cloud when breaking soundbarrier

basically the plane goes so fast that the air around the plane turns into a cone shape and starts to stretch to a point and then it breaks and now u have broken the soundbarrier

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