Werewolf (and friends!)

[Rosencrantz]

Typically, jet engines run on a very simple thermodynamic concept of mass flow rates. I'm assuming the plane's running on this kind of jet engine, so bear with me on this (since I need to regurgitate some of this information by next week during my thermo final!!!!!). Jet engines actually don't expel any gases that come from a combustion reaction, they're essentially spitting out the air that it intakes. Because a series of fans and a nozzle set-up are there to push the air along, it'll force the air out of the jet at a massive flow rate, propelling the jet.

Air's getting compressed in this system and has a force enacting on it due to the nozzle and the fans, respectively. Because this is happening, air tries to act like an ideal gas and will heat up immensely as a response to the compression and force. This isn't really mentioning how the fans also perform additional work on the air, giving it extra heat that doesn't come from the good ol' PV = mRT. So the air that expels from the engines will still be the same air that gets taken in, just that it's magnitudes hotter than the air going in.

Heated air, especially air that's hundreds of degrees hotter than room temperature, refracts light differently than cool air. You will see the heated track of air since light isn't being altered by the heated air medium as much as it does in cool air, so you see waves and dark spots and whatnot (remember: heated air is thin, so there's less molecules altering light waves).

You see the cloud stream at a later point because that's the point where the heated air affects the water molecules in the air. Water's fickle, it takes a shitton of energy to heat up water as compared to air (in fact, it takes up to four times as much energy to heat water), so you won't see the water particles explode into steam and into clouds until a few seconds after expulsion from the engine.

Also, that glow from the engines? That suggests combustion, but since we're talking jet streams, that light is coming from the superheated metal. Remember: hot metals glow, and that's what you see at the back of a jet engine (I mean, aside from a little bit of air combustion, but I don't know the details on that).




I might have just spouted out a ton of bullcrap and someone actually experienced in aeronautics will rip me to shreds for my explanation, but coming from what I'm learning in thermodynamics, I believe this is what's happening in those engines, and why we're not seeing jet clouds!!