Foo - 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.

REAAAALLLLYYYYY Good smelling gas. ahhhhh!!


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

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.

Nor does it have to be a jet.

http://home.att.net/~ww2aviation/B-17fl-1.JPG

The exhaust gives water particles something to hold onto creating a "cloud".

If I'm wrong, somebody will correct me.

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.

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.

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:

http://upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wingtip_condensation.jpg/800px-Wingtip_condensation.jpg

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:

http://upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wingtip_condensation.jpg/800px-Wingtip_condensation.jpg

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.

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.

Still a good chance it's a Chem Trail (http://en.wikipedia.org/wiki/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.

I have my tinfoil hat on, pal, try your disinformation on someone else.

:D :D :D

Marshmallow fluff.

Marshmallow fluff.
Best explanation yet! :)

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.

Contrails are cool...

http://www.nikonians-images.com/galleries/data/6968/219DSC_0653-med.jpg

http://www.nikonians-images.com/galleries/data/6968/219DSC_0690-med.jpg

http://www.nikonians-images.com/galleries/data/6968/219DSC_0591-med.jpg

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.

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.

Water vapour.

And/or a chem trail (http://en.wikipedia.org/wiki/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...

Contrails are cool...

Yeah, check out the B-17 propwash in this pic I took at the Watsonville airshow......


http://i162.photobucket.com/albums/t267/jd6572/B17_takeoff_1cleared.jpg

What does jet exhaust consist of?
Remnants of burnt jet fuel?

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.

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?

They've been seeding clouds and dusting crops long before any of these.

Yeah, check out the B-17 propwash in this pic I took at the Watsonville airshow......


http://i162.photobucket.com/albums/t267/jd6572/B17_takeoff_1cleared.jpg

Very cool.