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Ever seen vapor trails from bullets?
Rembrandt
Member Posts: 4,486 ✭✭
Found this on another site, thought it was very interesting. There have been a number of times I thought I saw the path of a bullet similar to a tracer round, here is a good explanation of this phenomon....
What is air?
It is a mixture of several gases - by volume;
Nitrogen 78.03%
Oxygen 20.99%
Argon 0.94%
Carbon dioxide 0.03%
Hydrogen 0.01%
Neon Trace
Helium Trace
Krypton Trace
Xenon Trace
Gas mixtures required properties are ( for industrial applications and compression) :
Specific volume
Density
Volume and mole percent
Molecular weight
Specific gravity
Partial pressure
Ratio of specific heats (k)
Pseudo critical pressure
Psuedo critical temperature
Compressibility
Gas constant
Specific heats
The MOLE;
The mole is a unit of measurement when working with gas mixtures. The specific volume and densiy of some gases are.
Gas---SpecVol cu.ft/mole-lb/mole-Spec.vol/cu.ft/lb.-Density
Hydrogen-379
2.016
188.3
.00531
Air
379
28.97
13.1
.0763
Isobutane-379
58.12
6.51
.153
The character of air changes according to temperature and humidity. The amount of "water" contained in air can be staggering. For example an air compressor takes in atmospheric air and compresses it. The intake volume is 1,000 cfm ( cubic feet per minute ) *{ Thats a fairly large compressor like those seen on construction sites}. The number of pounds of moisture per 1,000 cubic feet of saturated air at 14.7 lbs. absolute and temperatures shown;
Pressure
Temperature
Pounds of water per minute.
0
32F
0.3
0
70F
0.8
0
100F
2.8
On a really hot day 1/3 of a gallon of water is sucked into the intake of a compressor each MINUTE! After one hour's running that's .33 x 60 = 20 gallons or 4 - 5 gallon buckets of water.
The above is to illustrate what it is that a bullet travels through. It is pushing aside molecules of gases that can be laden with moisture. Not only are you able to see the "contrails" under some conditions, they can actually be photographed and often are in ballistics laboratories. Shadowgrams are produced. Different bullets leave different contrails and those trails take different forms depending upon the velocity at which the bullet is travelling. There is a distinct change in trails as the bullet passes up through, or down through, the speed of sound or the "sound barrier". A "stream can be seen coming off the bullets nose or ogive, in a "V" configuration. A second stream trace is seen coming from the base of the bullet. And a third stream is seen behind the bullet that looks like the wake from a boat in water. It is turbulence. I suppose the prow of a boat, as it cuts through water, could be likened to a bullet but just consider that the air and humidity is much thinner than the water.
So as the bullet progresses, or advances, it shoulders aside molecules of air and moisture and as it passes the void, or "vacuum" left behind is re-filled as the air collapses back into the void.
Some practical examples of air being pushed and water condensing are:
* You are standing on the berm of a highway when a tractor trailer passes. The blast of air almost knocks you off your feet.
* You pull into your driveway, your wife steps out of the car and exclaims - " what is all of that water running out from under the car, is there a leak? No, there isnt any leak. It's only condensation pouring off of the air conditioning system.
Under some lighting conditions, usually when the sun is low in the sky, a bullet can be seen traveling. That is sunlight reflecting from the copper jacket. An entirely different cause and effect related to light waves. Quite different than air and humidity related to moving gas molecules.
What is air?
It is a mixture of several gases - by volume;
Nitrogen 78.03%
Oxygen 20.99%
Argon 0.94%
Carbon dioxide 0.03%
Hydrogen 0.01%
Neon Trace
Helium Trace
Krypton Trace
Xenon Trace
Gas mixtures required properties are ( for industrial applications and compression) :
Specific volume
Density
Volume and mole percent
Molecular weight
Specific gravity
Partial pressure
Ratio of specific heats (k)
Pseudo critical pressure
Psuedo critical temperature
Compressibility
Gas constant
Specific heats
The MOLE;
The mole is a unit of measurement when working with gas mixtures. The specific volume and densiy of some gases are.
Gas---SpecVol cu.ft/mole-lb/mole-Spec.vol/cu.ft/lb.-Density
Hydrogen-379
2.016
188.3
.00531
Air
379
28.97
13.1
.0763
Isobutane-379
58.12
6.51
.153
The character of air changes according to temperature and humidity. The amount of "water" contained in air can be staggering. For example an air compressor takes in atmospheric air and compresses it. The intake volume is 1,000 cfm ( cubic feet per minute ) *{ Thats a fairly large compressor like those seen on construction sites}. The number of pounds of moisture per 1,000 cubic feet of saturated air at 14.7 lbs. absolute and temperatures shown;
Pressure
Temperature
Pounds of water per minute.
0
32F
0.3
0
70F
0.8
0
100F
2.8
On a really hot day 1/3 of a gallon of water is sucked into the intake of a compressor each MINUTE! After one hour's running that's .33 x 60 = 20 gallons or 4 - 5 gallon buckets of water.
The above is to illustrate what it is that a bullet travels through. It is pushing aside molecules of gases that can be laden with moisture. Not only are you able to see the "contrails" under some conditions, they can actually be photographed and often are in ballistics laboratories. Shadowgrams are produced. Different bullets leave different contrails and those trails take different forms depending upon the velocity at which the bullet is travelling. There is a distinct change in trails as the bullet passes up through, or down through, the speed of sound or the "sound barrier". A "stream can be seen coming off the bullets nose or ogive, in a "V" configuration. A second stream trace is seen coming from the base of the bullet. And a third stream is seen behind the bullet that looks like the wake from a boat in water. It is turbulence. I suppose the prow of a boat, as it cuts through water, could be likened to a bullet but just consider that the air and humidity is much thinner than the water.
So as the bullet progresses, or advances, it shoulders aside molecules of air and moisture and as it passes the void, or "vacuum" left behind is re-filled as the air collapses back into the void.
Some practical examples of air being pushed and water condensing are:
* You are standing on the berm of a highway when a tractor trailer passes. The blast of air almost knocks you off your feet.
* You pull into your driveway, your wife steps out of the car and exclaims - " what is all of that water running out from under the car, is there a leak? No, there isnt any leak. It's only condensation pouring off of the air conditioning system.
Under some lighting conditions, usually when the sun is low in the sky, a bullet can be seen traveling. That is sunlight reflecting from the copper jacket. An entirely different cause and effect related to light waves. Quite different than air and humidity related to moving gas molecules.
Comments
The most important things, Are not things.
SSgt Ryan E. Roberts, USMC
"It was like that when I got here".
The most important things, Are not things.
That reminds me of when I used to shoot on the Mass. rifle team. We used to call it the Wake. That was pretty neat, like you say. You could predict where each shot would hit. Memorys, memorys.
Gino
"If All Else Fails, Read The Directions"
Another explaination is possible, the spotters are seeing the wake of the bullet, and not a contrail, and the behind the bullet position makes the wake much more visible.
"If you ain't got pictures, I wasn't there."
Edited by - Alpine on 06/06/2002 10:07:51
Margaret Thatcher
"There are three kinds of lies: lies, damned lies and statistics."
Mark Twain
Isnt it incredible how that seems so obvious once you've been taught to look for it and learn to read it, when before you were told of it, you probably never saw it, or even heard of it, much less thought it possible? That arc is pretty cool VH, gets to be pretty pronounced at the longer distances, I've never seen the .50 cal. vapor trail, havent had time to look for it when I've shot it. I'd like to shoot a target gun in .50, all I've shot is the M2. I honestly cant remember if I could see the .223's trail, but I think so, I know I saw the .308's trail, very easy to see. It would be interesting to see the diff. in trails from one cal. to another, and even in bullets the same size, but at faster speeds depending on their chambering, all on the firing line at the same time, with the same weather and everything, would be a good video opportunity.
SSgt Ryan E. Roberts, USMC
Saw a '06 bullet once. Moved jist in time.
Clouder..
When Clinton left office they gave him a 21 gun salute. Its a damn shame they all missed....
When Clinton left office they gave him a 21 gun salute. Its a damn shame they all missed....
Wild Turkey"if your only tool is a hammer, you tend to see every problem as a nail"
Tank cannon (before advent of fin stabilized rounds) also had to adjust for the movement to side due to spin at long ranges.
If you want to do some mind boggling math, try figuring the Kinetic Energy and heat generated when a 15 lb penetrator hits armor plate at 5000 fps----
Wild Turkey"if your only tool is a hammer, you tend to see every problem as a nail"
R.I.P 45, 28, 3
BNRVA@aol.comwww.vcdl.org