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  1. #1
    la vache fantŰme phantomcow2's Avatar
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    What does jet exhaust consist of?

    When you see a jet fly overhead and it leaves a long white streak behind it that looks like a linear cloud, what exactly IS that? Is it water vapor?
    And how come not all planes do it, I haven't seen a passenger aircraft do it.
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  2. #2
    Senior Member sweetnsourbkr's Avatar
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    REAAAALLLLYYYYY Good smelling gas. ahhhhh!!


    http://en.wikipedia.org/wiki/Contrail

  3. #3
    phony collective progress x136's Avatar
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    Yep, water vapour, and passenger jets do it all the time. It's not that some planes do it and some don't, it's just that the conditions in the atmosphere need to be right for it to happen.

  4. #4
    Packfodding 3 caloso's Avatar
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    Nor does it have to be a jet.

    Cyclists of the world, unite! You have nothing to lube but your chains!

  5. #5
    Giving you the business. Cypress's Avatar
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    The exhaust gives water particles something to hold onto creating a "cloud".

    If I'm wrong, somebody will correct me.
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    Dear Cypress,

    You have received an infraction at Bike Forums.

  6. #6
    Senior Member ryder47's Avatar
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    Quote Originally Posted by phantomcow2
    When you see a jet fly overhead and it leaves a long white streak behind it that looks like a linear cloud, what exactly IS that? Is it water vapor?
    And how come not all planes do it, I haven't seen a passenger aircraft do it.

    They're actually called contrails and form through the injection of water vapor into the atmosphere by exhaust fumes from a an engine. If atmospheric conditions (humidity, temperature, etc .) and the water vapor in the exhaust are just right, ice crystals will develop which is what we're actually seeing.

  7. #7
    Dolce far niente bigbossman's Avatar
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    Quote Originally Posted by ryder47
    They're actually called contrails and form through the injection of water vapor into the atmosphere by exhaust fumes from a jet engine. If atmospheric conditions (humidity, temperature, etc .) and the water vapor in the exhaust are just right, ice crystals will develop which is what we're actually seeing.
    Yup. The exhaust is warm air, and contains moisture. When the warm air in the exhaust exits the motor and is chilled, the moisture condenses out. If it is cold enough, it condenses out in the form of ice crystals.

    Warm air has a much larger capacity to hold moisture than cold air does.
    "Love is not the dying moan of a distant violin, itís the triumphant twang of a bedspring."

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  8. #8
    Packfodding 3 caloso's Avatar
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    Quote Originally Posted by Cypress
    The exhaust gives water particles something to hold onto creating a "cloud".

    If I'm wrong, somebody will correct me.
    I think all that's required is the rapid change in air pressure that causes the water to condense. That's why you'll see contrails off of wingtips:

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  9. #9
    Senior Member ryder47's Avatar
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    Quote Originally Posted by caloso
    I think all that's required is the rapid change in air pressure that causes the water to condense. That's why you'll see contrails off of wingtips:

    I stuck to the engines as a water vapor source and the atmoshperic conditions to explain the presence of contrails from the engines.

    Point taken with the contrails on the wing surfaces and you're correct as there is a pressure drop there causing a temperature drop as well (pressure drops equal temperature drops). The temperature drops below the dewpoint of the air and moisture condenses within the confines of this area.

  10. #10
    Videre non videri
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    Water vapour, carbon dioxide, nitrogen oxides ("NOx"), hydrocarbon particulates ("HC"), minor amounts of other compounds created during the combustion (CO, sulphuric compounds, et c) and finally a lot of hot air.

    When the water vapour exits the exhaust, the air there is hot and able to hold large amounts of water vapour. Some distance behind the exhaust, the air has cooled to the point where relative humidity reaches 100%, and water begins to condense out of the air, forming tiny droplets that instantly freeze to form ice. Or more likely, it forms ice directly from the vapour through sublimation.

    If the air at the aircraft's altitude is dry, the condensation trail disappears a shorter distance behind the aircraft, but if the air there is humid, the trail not only remains, it also often acts as a nucleation core for further condensation/sublimation, eventually forming large bands of high-altitude clouds across the sky.

    And as has been pointed out, it doesn't have to be a jet. Any engine burning hydrocarbons will produce a trail given the proper circumstances.

  11. #11
    Videre non videri
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    Quote Originally Posted by BugsInMyTeeth
    Still a good chance it's a Chem Trail though...
    The "chemtrail" CT is one of the nuttiest I've come across. It's so silly and stupid that I don't know how it could even have got started in the first place.

  12. #12
    Videre non videri
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    Quote Originally Posted by BugsInMyTeeth
    I have my tinfoil hat on, pal, try your disinformation on someone else.

  13. #13
    Faster but still slow slowandsteady's Avatar
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    Marshmallow fluff.
    "Ride lots." -- Eddy Merckx

  14. #14
    Senior Member sweetnsourbkr's Avatar
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    Quote Originally Posted by slowandsteady
    Marshmallow fluff.
    Best explanation yet!

  15. #15
    Senior Member Michigander's Avatar
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    Quote Originally Posted by CdCf
    The "chemtrail" CT is one of the nuttiest I've come across. It's so silly and stupid that I don't know how it could even have got started in the first place.
    I won't say I believe that crap because I don't. But I have seen the federal government do stupider **** in person.
    Bring back the Sig Test!


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  16. #16
    Senior Member avmanansala's Avatar
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    Contrails are cool...






  17. #17
    J E R S E Y S B E S T Jerseysbest's Avatar
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    I think I've posted this on here before, but...

    According to one of my climate professors, after the events that happened on September 11, 2001 when all planes were grounded except for Air Force One, the satellite images of the atmosphere were either not released or confiscated or something because you could tell where Air Force One was flying since they were the only ones leaving contrails in the sky.
    Quote Originally Posted by SingingSabre View Post
    Cheating: a symptom of the problem.

  18. #18
    Senior Member Michigander's Avatar
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    My dad's side of the family has a long standing tradition of serving in the air force, and they never mentioned such things. Wouldn't surprise me though, thats for damn sure. The one thing that can be counted on is the feds lying, and often doing things that are a direct hazard to civilians.
    Bring back the Sig Test!


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  19. #19
    Banned. timmyquest's Avatar
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    Quote Originally Posted by BugsInMyTeeth
    Water vapour.

    And/or a chem trail

    Passenger jets do it, which are probably the majority of the planes you see in the sky. Why do you say that passenger jets don't leave a trail?


    The craft needs to have a relatively high altitude.
    It depends on where you live.

    I'm about a 10 min flight northwest of O'Hare when at home and about 300 miles away when i'm at school and the difference in what i see is drastic as you would imagine.

    All planes do it though...

  20. #20
    Dolce far niente bigbossman's Avatar
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    Quote Originally Posted by avmanansala
    Contrails are cool...
    Yeah, check out the B-17 propwash in this pic I took at the Watsonville airshow......


    "Love is not the dying moan of a distant violin, itís the triumphant twang of a bedspring."

    S. J. Perelman

  21. #21
    On my TARDIScycle! KingTermite's Avatar
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    Quote Originally Posted by phantomcow2
    What does jet exhaust consist of?
    Remnants of burnt jet fuel?
    Quote Originally Posted by coffeecake View Post
    - it's pretty well established that Hitler was an *******.

  22. #22
    Senior Member DannoXYZ's Avatar
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    Check out these patents...

    United States Patent #4,686,605 / Eastlund / August 11, 1987
    Method and apparatus for altering a region in the earth's atmosphere, ionosphere, and/or magnetosphere

    United States Patent #6,315,213 / Cordani / November 13, 2001
    Method of modifying weather

    United States Patent #5,286,979 / Berliner / February 15, 1994
    Process for absorbing ultraviolet radiation using dispersed melanin

    United States Patent #4,948,050 / Picot / August 14, 1990
    Liquid atomizing apparatus for aerial spraying

    United States Patent #4,412,654 Yates / November 1, 1983
    Laminar microjet atomizer and method of aerial spraying of liquids

    United States Patent: #US3813875 / Issued/Filed Dates: June 4, 1974 / April 28, 1972
    Rocket having barium release system to create ion clouds in upper atmosphere.

  23. #23
    Senior Member Michigander's Avatar
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    Quote Originally Posted by DannoXYZ
    Check out these patents...

    United States Patent #4,686,605 / Eastlund / August 11, 1987
    Method and apparatus for altering a region in the earth's atmosphere, ionosphere, and/or magnetosphere

    United States Patent #6,315,213 / Cordani / November 13, 2001
    Method of modifying weather

    United States Patent #5,286,979 / Berliner / February 15, 1994
    Process for absorbing ultraviolet radiation using dispersed melanin

    United States Patent #4,948,050 / Picot / August 14, 1990
    Liquid atomizing apparatus for aerial spraying

    United States Patent #4,412,654 Yates / November 1, 1983
    Laminar microjet atomizer and method of aerial spraying of liquids

    United States Patent: #US3813875 / Issued/Filed Dates: June 4, 1974 / April 28, 1972
    Rocket having barium release system to create ion clouds in upper atmosphere.
    Does that mean I should throw on my respirator with some organic filters every time a plane passes by?
    Bring back the Sig Test!


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  24. #24
    Packfodding 3 caloso's Avatar
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    They've been seeding clouds and dusting crops long before any of these.
    Cyclists of the world, unite! You have nothing to lube but your chains!

  25. #25
    Senior Member avmanansala's Avatar
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    Quote Originally Posted by bigbossman
    Yeah, check out the B-17 propwash in this pic I took at the Watsonville airshow......


    Very cool.

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