Would a Flying Saucer leave a contrail?

ktesibios said:
Contrails can be formed by the drop in pressure caused by the passage of a wing through the air, if the air is cold and humid enough.
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True, I often see those coming off the edges of extended flaps when a plane is coming in for a landing on a humid day.

But the contrails that you usually see up high in the sky are water vapor from combusted fuel, condensing in the cool air up there.
 
A 747 at altitude, leaving contrails from the motors, the wingtips, and the wing close to the fuselage.
I've seen this several times.
 

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FramerDave said:
Then that's one point in your wife's favor.

Please keep in mind I'm not really taking this seriously. I think that chances of UFO's being extraterrestrial craft under intelligent control are about as good as unicorns prancing out of my butt.
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So, do they? The invisible ones of course!:)
 
Gord_in_Toronto said:
Contrary to the general consensus to date in this thread, you do not necessarily need jet engines to create contrails. They can be triggered by any object passing through supercooled moist air.
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THIS.

Anything that creates trailing vortices as it moves through the air (which is pretty much anything because if the object doesn't generate any lift it won't move through the air but fall to the ground) is capable of producing a visible vapour trail. The core of a vortex is a low pressure area, and as it forms it causes a drop in temperature. As a result water vapour naturally in the air at the location of the vortex core can condense. In fact the pressure and temperature drop inside a vortex core can be so severe that the water vapour freezes into ice crystals.

This can be readily observed in photographs of WW2 prop-driven bomber aircraft such as the B-17, which created very visible vapour trails, despite lacking the hot exhaust gasses of a jet airliner. It can also be observed from the wing tips of aircraft. The shorter and stubbier the wings of the aircraft, the larger the vortices will be, and the more likely they will produce a visible trail.
 
Drewbot said:
Would a Flying Saucer leave a contrail?
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Like most things in life, which woo-ists usually can't understand, the answer is, "It depends."

Even the less technical people here can recall the little they remember from high school (that's the unused brain cells where I found it) and can enumerate some of the many ways a powerplant, with explainable or (the answer is never "The aliens done it, I tells ya!") not-entirely-explainable mechanisms, might leave or not leave a "chemtrail" (love the half-ass-ed-ness of it!). Fortunately for thems of us what enjoy the woo, they often dig into it with snow shovels. And are usually so completely wrong their great-grandfathers call out from beyond the grave, "You moron! That was just a tale I told your grandpa and his brothers and sisters to scare them enough that I could get some sleep."

Grandpa Heinie was mostly pre-technology so his story regarding some guys who met each year to honor the deaths of their brothers, but then one ended up like the others on the roof hammering with a mallet.

Grandpa stole it from Bennett Cerf.
 
FramerDave said:
Then that's one point in your wife's favor.

Please keep in mind I'm not really taking this seriously. I think that chances of UFO's being extraterrestrial craft under intelligent control are about as good as unicorns prancing out of my butt.
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Please maintain 24/7 video surveillance should you anticipate any prancing unicorns.:eek:
 
Increasing and decreasing pressures cause some pretty looking water vapors.
Any quick directional change will lower the temp close to the wings creating a water vapor.
 
gumboot said:
This can be readily observed in photographs of WW2 prop-driven bomber aircraft such as the B-17, which created very visible vapour trails, despite lacking the hot exhaust gasses of a jet airliner.
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Really? I think the contrails in this photo are from the engine exhaust.
 
Well, mine does, but then again, it's a pretty old UFO, so maybe the newer ones are contrail-free. They sure don't make them like they used to back in the 50's.
 
Bell said:
I think you saw the chemtrail's shadow.

That, or Obama want's to get more control over and compliance from the white people.
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.
These are common....
 

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gumboot said:
I can't see that photo, but here is an example.
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Those look like prop vortices, and wing tip vortices.
Very cool.

ETA: Vapor trails from the leading edges and right over the horizontal stabilizers in high lift and G maneuvers can look really neat. Sometimes it covers the whole wing surface.
I agree with your post #24. For sure
Contrails are just streaks of these water vapors.
 
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CurtC said:
Here's the photo I was trying to post:

http://contrailscience.com/wwii-contrails/

I thought those were trails from the exhaust, but the pic gumboot just posted makes me wonder.
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It could be that both produces contrails, but in all of the photos that I've seen that were close enough to distinguish, the contrail came off the aircraft quite thick and dissipated, like those coming off the props. Further, they mostly seem to be above the wing as well as below, whereas the exhaust on the B-17 is below the wing so exhaust contrails should only be below.

I imagine it depends on atmospheric conditions and all that. Vortex contrails tend to form in warmer humid air (plenty of water vapour in the vortex core, and greater opportunity for a temperature drop inside the core) whereas exhaust contrails probably form better in dry cold air (contrasting more with the warm humid exhaust from the aircraft).
 
You don't need a jet exhaust to make a contrail.

You don't need an exhaust of any kind.

Or a wing.

You don't even have to be flying.

Vortex.jpg

Well, that sucks.​


NASA​
 
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