> “They are jet vapor trails, or exhaust trails. I have seen them for years and years.”
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Turbine exhaust has no solids; its all water, co2 and hydrocarbons. A missile’s exhaust, on the other hand has considerable solid content, and shows up perfectly whether the atmosphere is cool or warm. They also have the distinctive helix caused by the mixing nozzle.
Well, gee ... where do we start with that train wreck of a comment?
You start out apparently talking about solid rocket motors -- but those don't have "mixing nozzles," because the combustion only occurs on the exposed surface of the solid propellant. So there couldn't be a "distinctive helix" in that case.
Which leaves us with liquid-fueled rockets -- which advanced countries, including China, do not use for ballistic missiles.
Worse for you, liquid fueled rockets generally use Hydrogen and Oxygen, which produces nothing but water. Some use LOX and Kerosene, the exhaust of which is essentially the same as turbine exhaust, which you have already ruled out.
And there are no "mixing nozzles" in a rocket engine. There are injector plates, which spray fuel and oxidizer into the combustion chamber in a manner designed to optimize mixing. And "distinctive helix pattern" caused by the injector system would indicate a very significant flaw in the rocket engine.
To sum it up .... you're completely and utterly incorrect.