Vapor trails, military or commuter aircraft?

We have all seen the vapor trails left in the sky being formed behind very high flying aircraft. I believe this is formed from the moisture in a jet’s exhaust.

My question is what type of planes produce these cloud like lines in the sky?

Does your average commuter jet flying at 35,000 feet cause this, or does the craft need to be flying at very high altitude like military AWACS, bombers and the like?

All jet aircraft flying high enough and under the right conditions will create contrails. They are caused by water vapor condnesing on small particles present in the jet exhaust. If you look at one being formed through binoculars, you can see that the condensation begins to occur several dozen feet behind the engine, since the exhaust gasses need to cool before condensation can happen.

I personally found many of the posts in a previous thread Contrails to be one of the better ones of the myriad of threads.

Thanks Q.E.D. but, I think we all know how they are formed.
That wasn’t the question.
I guess I need to rephrase it!
Under normal conditions will a commuter jetliner flying at 35k feet create contrails? Or are the vast majority of the ones I see created by high flying military jets?
I am just trying to settle an argument.

Depends on the atmospheric conditions. Some open-wheeled race cars can produce contrail-like effects (IANAM, so I don’t know if they are technically contrails or not) under the right conditions. Generally, they have high speeds and to-the-letter aerodynamics that create the right pressures coming off the rear wings. Given the proper humidity and speeds, they are capable of producing a short contrail.

As for aircraft, I’ve no clue, but “normal conditions” isn’t a very accurate term… normal conditions where? Los Angeles, or Boston? Over an ocean, or inland?

Yes, commercial aircraft at 35,000 feet can and do produce contrails. In fact most of the ones you see are just that, in fact. Just as in a cloud chamber used to study charged particles, the atmosphere the aircraft passes through must be supersaturated, that is contain more water vapor than the vapor pressure would normally allow at the ambient temperature.

And not everyone knows how they are formed. I’m sure a few people who read that post did not.

It’s not limted to jets, either. Piston engine propeller aircraft can produce contrails.

As per Joey’s comment above, look at some photos of the air battles over Germany during WWII. B-17s and Messerschmitts produced contrails.

Space Shuttle? Pure exhaust or some vapor contrail as it climbs?

Apparently not, because you and QED mentioned two different mechanisms. Are contrails made up of water contained in the jet exhaust, or was the water already in the atmosphere waiting for a nucleation site?

Contrails usually form between 20,000 and 35,000 feet. Aircraft above that usually do not form contrails.

Many aircraft can get to 20,000 + feet. Most ‘Commuters’ do not go above 20,000 due to their short leg length. Some do. Most can if they wanted or needed to. So as to the OP, most contrails are not made by commuter aircraft but by regular airline travel and military aircraft. By and large, most contrails now days are caused by the average airliner as they are the ones that spend the most time in the correct altitudes to form them.

I have had a Cessna 310 Turbo to 31, 000 feet and was forming contrails and it was snowing inside the cockpit. There are no absolute answers.
It was a test flight. ::: Do not try it without proper training.::: :smack:

Commercial airliners can and do produce contrails. If you see several contrails together they are probably military. If you see contrails turning and doing other maneuvers they are probably military. If you see a contrail that goes straight across the sky, or part of it, without deviation it could be either but chances are it is a commercial airliner.

So with this much public knowledge on contrails why are there <i>so</i> many conspiracy theories about them?

This was actually a pretty big deal to the bombers. Contrails amounted to a big arrow in the sky pointing the bombers out to the gunners below (or made it easier for intercepting aircraft to spot the bombers). Sometimes the bombers would be able to change altitude to get rid of them but not always which was bad luck for the bomber crews.

While not a contrail this is a cool picture of condensation happening on a supersonic jet. There are other such cool pictures linked at this site.Transonic condensation

Conspiracy theories are undeterred by facts, public or otherwise. If you are convinced of some sort of coverup or fraud, you won’t let mere facts change your mind.

Also, there’s performance aircraft like the Blue Angels or the Thunderbirds. They generally have special devices to produce contrail-like trails, so the air show audiences can see them better and ooh and aah over them. Of course, as Whack-a-Mole points out, this is not something you want in a combat zone.

The great majority of contrails you see are commercial traffic. In fact, when all US air traffic was grounded after 9/11, the astronauts on the International Space Station noted the skies below were clear. Remember that the military air traffic was increased at that time. That lack of commercial air traffic allowed researchers to calculate the effect contrails have on the athmosphere’s heat budget.

Are people just very paranoid or are these Contrails really being mistaken for Chemtrails. Since I started this thread and tried to do a little research (all to settle a bet) I have been overwhelmed with conspiracy theories! The reason I asked the question in the first place was because I noticed an increase in the contrails being formed in the skies above NYC. Apparently I am not the only one seeing them. There must be some 50 web sites screaming conspiracy.
They believe that the government is putting chemicals in the atmosphere to control the population. Do people really believe this to be the case? Any Dopers believe this?

Here are some sites:

Correction, there are some 20,000 hits for Chemtrails.
This one speaks for it’s self!

Damn! Are these the same people that believe in Bigfoot?

I’m sorry , broken link;
Here it is!