[TWEAKED] Contrails for objects without propulsion

[Quark73]

Hello,
I like the contrails notification feature very much. But it is IMHO not always plausible. It seems the size of the contrails depends only on the size of the aircraft, not size or propulsion. See attached save.file. The spy balloon and the nuclear driven helios jammer causing large contrails.
This applies for missiles too, regardless if in booster or coaster phase of flight. I am aware that contrails can be also induced by pure turbulance, but these contrails are significantly smaller and less durable than conventional contrails caused by burned fuel.

Bild_2024-09-04_003010172.png (53.61 KiB) Viewed 832 times

[caelunshun]

On a similar note, missiles in space generate contrails currently, which is pretty amusing. Though I think the effect on gameplay is negligible.

[Quark73]

On a similar note, missiles in space generate contrails currently, which is pretty amusing. Though I think the effect on gameplay is negligible.

It does IMHO, this makes incoming missile detection way to optimistic. In most cases a coasting missile would hit you out of the blue as long you have no other indications like EW or radar.

[Dimitris]

That's useful information, thanks. The airship contrail is clearly an oversight. Ditto for exo-atmospheric objects.

On the missile point: Are unpowered but high-speed objects in the upper atmosphere not able to generate contrails?

I have seen, for instance, multiple videos of RVs leaving clearly visible trail paths on their atmospheric re-entry. And Space Shuttle re-entries likewise are/were notorious for being easily tracked visually.

Is there a Mach threshold?

[Quark73]

1.) On the missile point: Are unpowered but high-speed objects in the upper atmosphere not able to generate contrails?

2.) I have seen, for instance, multiple videos of RVs leaving clearly visible trail paths on their atmospheric re-entry. And Space Shuttle re-entries likewise are/were notorious for being easily tracked visually.

Is there a Mach threshold?

1.) Basically no combustion no contrail, since there is nothing to mix for making mixing cloud. Missiles have by nature few wake turbulence therefor no wake induced trails.

2.) This is IMHO a different effect. The heating during re-entry causes a plasma. Acc. wikipedia Here the main heating takes place between 213 and 155 kft.

[Dimitris]

Alright, thanks again.

[CV60]

On a similar note, missiles in space generate contrails currently, which is pretty amusing. Though I think the effect on gameplay is negligible.

I disagree. Spacecraft leaving contrails in space is a well documented phenomenon. For example, see this:
https://youtu.be/G3vONUX_0sI?t=72

[Nikel]

I suppose this is too detail for the game, but there is a lot of scientific info on contrails in this link.

https://www.fzt.haw-hamburg.de/pers/Sch ... egert.html



More light and with beautiful pics.

https://www.space.com/what-are-contrails

[rmeckman]

1.) On the missile point: Are unpowered but high-speed objects in the upper atmosphere not able to generate contrails?

2.) I have seen, for instance, multiple videos of RVs leaving clearly visible trail paths on their atmospheric re-entry. And Space Shuttle re-entries likewise are/were notorious for being easily tracked visually.

Is there a Mach threshold?

1.) Basically no combustion no contrail, since there is nothing to mix for making mixing cloud. Missiles have by nature few wake turbulence therefor no wake induced trails.

2.) This is IMHO a different effect. The heating during re-entry causes a plasma. Acc. wikipedia Here the main heating takes place between 213 and 155 kft.

It is true that the term contrail applies specifically to mixing clouds consisting of water droplets or ice crystals. But there are other processes that can produce visible plumes trailing behind moving objects. For RVs, it may be a combination of plasma and smoke associated with the ablation of the heat shield. For rockets and missiles, combustion of the propellant may result in a trailing smoke plume depending on the properties of the combustion products. Ships are often first visually detected by the smoke from their stacks. These non-contrail plumes can still affect unit detection.

[boogabooga]

On a similar note, missiles in space generate contrails currently, which is pretty amusing. Though I think the effect on gameplay is negligible.

If the rocket motor is firing, missiles in space can very much generate contrails of sorts. This is especially true during dusk or dawn when the the contrail can scatter direct sunlight, though the sky is still dark for the observer on the ground. The infamous Norwegian spiral is an example:
https://www.youtube.com/watch?v=2mUXBqJbQKg

On the missile point: Are unpowered but high-speed objects in the upper atmosphere not able to generate contrails?

I have seen, for instance, multiple videos of RVs leaving clearly visible trail paths on their atmospheric re-entry. And Space Shuttle re-entries likewise are/were notorious for being easily tracked visually.

Yes, both the plasma and the "contrail" (be it ablating material, etc.) seem pretty obvious all the way to impact:
https://www.youtube.com/watch?v=2a1acYZ93yc

The shuttle is much larger than an average RV, though.

Is there a Mach threshold?

Yes, there would be, but I'm not sure what it is.

SpaceX Starship livestreams have the feature of displaying a video feed of a re-entering upper stage together with velocity data:
https://youtu.be/OZVR2SNjyug?t=5110

This one was hard to see, but I think in concept you could use these kinds of feeds to gage plasma/ablation level vs. velocity.

[Dimitris]

Numerous tweaks on this subject for the next build:
- Contrails cannot be formed outside the atmosphere
- The temperature-at-altitude is now calculated dynamically from the sea-level temperature, using the US standard atmosphere model, so the altitude threshold for contrails forming now varies with the time-of-day and local surface temperature. (The temperature can vary widely with altitude: https://apollo.nvu.vsc.edu/classes/met1 ... t_temp.gif )
- Airships and other craft using non-combustion propulsion (e.g. pure-coasting or nuclear) do not generate contrails
- Weapons using boost-coast propulsion generate contrails only during their boost duration. Weapons using "cruise" propulsion (e.g. turbojet or piston/turboprop) can generate contrails throughout their flight
- Contrails cannot form at temperatures above -40C. There is a "transition" layer between -40C and -50C temperature at which contrails can be formed but are weaker than at lower temperatures; this is reflected by lowering the visual size of the generated contrail by one magnitude (e.g. medium to small).

[Kobu]

Very good feature, especially this one:

Weapons using boost-coast propulsion generate contrails only during their boost duration.

[Quark73]

Sounds good, thank you. I am curious how this works out on air combat.

[Kobu]

Sounds good, thank you. I am curious how this works out on air combat.

I hope to see more fighters/planes shot down without knowing that a missile is headed towards them. Previously, they were detected by the contrail when the missile's engine was already off, which was not very realistic.

[Blast33]

Good stuff!