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Eliminating contrails from flying could be cheap

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Re: Eliminating contrails from flying could be cheap

#141

Post by nine_k »

aeternum wrote: post #130
nine_k wrote: post #106

Earlier quoted context omitted.

Numbers don't add up. If you take a 8K camera with a standard 50 mm lens, its angular resolution is about 20" / pixel. A 50 mm lens has a FOV of about 40°. It covers a cone of about 0.38 strad. A full hemisphere has 2·pi = 6.28 strad, so we need at least 16.5 such cones to cover the whole area; actually we need likely 20-25 because of imperfect geometry and some safety margins at intersections. We can, of course, mou…

Most camera sensors already detect in the IR range, you just need to remove the filter. I've done it, works great and pretty fun to convert some old webcams, robot vacuums lidar scanners look especially cool. Blurry video is fine when using techniques like this: https://www.youtube.com/watch?v=m-b51C82-UE Clouds also don't save you (unless you have two thick layers to fly through) because this technique is even easie…

Does a consumer-grade 8K camera sensor detect a 20°C difference in a few pixels? Cameras have to aggressively fight against thermal noise. Visible light is much more energetic than IR; detecting a faint IR signal with a sensor which is about as hot as the object it's looking at is hard. You need to cool the sensor down; old military aircraft even carried a tank of liquid nitrogen for that.

I mean, yes, you can take a low-noise sensor, add cooling, add a telescope lens so that you'd see the shape more readily, put a bunch of these telescopes on a rotating platform to scan the sky, etc. This is doable, but the thread started with an idea that it's doable with consumer-grade ("cheap") tech. I doubt that.

While at it, even if we assume that stealth does not exist for fast and heavy aircraft, it seems to effectively exist for slow, lighter-weight drones. Ukrainian drones, built from ultralight aircraft like Aeroprakt A-20, somehow penetrate 700 miles into Russian territory to burn refineries. With a cruise speed of 70 mph (sic), it should take them 10 hours to fly this distance. Were they detected efficiently, that would be enough time to scramble an interceptor a hundred times. Apparently this does not happen.

Re: Eliminating contrails from flying could be cheap

#142

Post by topaz0 »

klodolph wrote: post #111
DoctorOetker wrote: post #101

N2O (laughing gas) is not combustible, but autodecomposes into a mixture composed of 1 part oxygen gas and 2 parts nitrogen gas, which happens to be the approximate composition of the atmosphere. In theory we could design and use N2O engines and airplanes etc, and their exhaust could be a gas that is nearly equivalent to atmospheric composition. One important issue is making sure all the N2O has decomposed because it…

Someone can break out their chemistry references, but I think N₂O is probably not workable as a fuel (or at best, not very good). It forms naturally in internal combustion engines, from air, at the temperature and pressures found in engines, given O₂ and N₂. If something has the habit of forming in an engine, I don’t think you could use it as fuel, but my thermodynamics is a bit too rusty to do any kind of ELI5 and I…

You're probably thinking of NO2, which is indeed a pollutant that results from overly hot combustion in air. N2O is in fact used in engines, but it is not the fuel -- rather it is a supplementary oxidizer, which allows you to burn more fuel and therefore produce more power than you could if you only had the oxygen from air. At any rate, that means using N2O won't be a solution to the aircraft fuel problem -- you'd still need a combustible fuel for it to oxidize.

Re: Eliminating contrails from flying could be cheap

#143

Post by petschge »

nine_k wrote: post #106
aeternum wrote: post #94

Earlier quoted context omitted.

This seems pretty useless in an age with super cheap 8k cameras and novice ability to do a delta-recorded image.

Numbers don't add up. If you take a 8K camera with a standard 50 mm lens, its angular resolution is about 20" / pixel. A 50 mm lens has a FOV of about 40°. It covers a cone of about 0.38 strad. A full hemisphere has 2·pi = 6.28 strad, so we need at least 16.5 such cones to cover the whole area; actually we need likely 20-25 because of imperfect geometry and some safety margins at intersections. We can, of course, mou…

You don't need to identify the A320 from 15 pixels. Once you see a 15 pixel signature that changes between subsequent frames you point the one extra camera on a movable mount with a 600mm lens on it at it. Now you get a few hundred pixels.

Re: Eliminating contrails from flying could be cheap

#144

Post by baggy_trough »

counters wrote: post #67
Nzen wrote: post #10

Earlier quoted context omitted.

Likewise. In fact, I was under the opposite impression because of the benefit that sulfur enriched shipping exhaust had for our climate [0]. It looks like these clouds are thinner and don't have the same impact as that, though. While I felt that the featured article linked to their favorite site aggressively (four links to contrails.org), it looks like the google site is legitimate [1]. I couldn't find a recent [2] p…

> In fact, I was under the opposite impression because of the benefit that sulfur enriched shipping exhaust had for our climate. It isn't quite accurate to state that ship tracks have/had a "benefit" on our climate. Their existence creates a transient decrease in OLR and increase in albedo. If anything, they simply masked some GHG-induced warming that had a much longer half-time, and cleaning up ship emissions has "u…

The benefit was that they cooled the climate.

Re: Eliminating contrails from flying could be cheap

#145

Post by aeternum »

nine_k wrote: post #141
aeternum wrote: post #130

Earlier quoted context omitted.

Most camera sensors already detect in the IR range, you just need to remove the filter. I've done it, works great and pretty fun to convert some old webcams, robot vacuums lidar scanners look especially cool. Blurry video is fine when using techniques like this: https://www.youtube.com/watch?v=m-b51C82-UE Clouds also don't save you (unless you have two thick layers to fly through) because this technique is even easie…

Does a consumer-grade 8K camera sensor detect a 20°C difference in a few pixels? Cameras have to aggressively fight against thermal noise. Visible light is much more energetic than IR; detecting a faint IR signal with a sensor which is about as hot as the object it's looking at is hard. You need to cool the sensor down; old military aircraft even carried a tank of liquid nitrogen for that. I mean, yes, you can take a…

How many of those attacks were successful? Russia has fairly advanced radar that is quite capable of picking up a plane like that. I think the more likely explanation is that it was incorrectly deemed not a threat or a minor threat.

700 miles is far more than the standard range of the A-20 (210nm). Is it possible they launched it from well within Russia thereby making it much less likely to be considered a threat?

Re: Eliminating contrails from flying could be cheap

#146

Post by Tor3 »

aeternum wrote: post #130
nine_k wrote: post #106

Earlier quoted context omitted.

Numbers don't add up. If you take a 8K camera with a standard 50 mm lens, its angular resolution is about 20" / pixel. A 50 mm lens has a FOV of about 40°. It covers a cone of about 0.38 strad. A full hemisphere has 2·pi = 6.28 strad, so we need at least 16.5 such cones to cover the whole area; actually we need likely 20-25 because of imperfect geometry and some safety margins at intersections. We can, of course, mou…

Most camera sensors already detect in the IR range, you just need to remove the filter. I've done it, works great and pretty fun to convert some old webcams, robot vacuums lidar scanners look especially cool. Blurry video is fine when using techniques like this: https://www.youtube.com/watch?v=m-b51C82-UE Clouds also don't save you (unless you have two thick layers to fly through) because this technique is even easie…

"Clouds also don't save you (unless you have two thick layers to fly through) because this technique is even easier with satellites."

This is incorrect. A typical satellite will orbit once every 100 minutes or so (military spy satellites more often because they fly lower, but that only makes the next part even worse). To have any kind of resolution the swath it can scan is very narrow. It'll pass from horizon to horizon in some 10-14 minutes or so, if if passes reasonably overhead (which it'll do once, the next orbit it'll be far from overhead or not seen at all, depending on your latitude).

For a satellite to spot an airplane you need to be in luck. A coincidence. It's not something you can use for spotting airplanes. The harder you look (the more you increase resolution) the more narrow the swath gets. You can have more satellites. There's still no chance of actively detecting airplanes on a regular basis. And this doesn't even take into consideration that the data must be processed after having been dumped from the satellite. The satellite is by then elsewhere.

You could use a geostationary satellite, to monitor a good third of the planet at once. But then you're nearly 36000km above equator and you can't see any details. So, not that either.

Satellites are great for scanning the surface of the planet. And for that we're now at a stage where it's hard to hide anything, for very long at least. But moving airplanes is something entirely different.

(My job is about processing data from satellites).

Re: Eliminating contrails from flying could be cheap

#147

Post by LargoLasskhyfv »

DoctorOetker wrote: post #101

N2O (laughing gas) is not combustible, but autodecomposes into a mixture composed of 1 part oxygen gas and 2 parts nitrogen gas, which happens to be the approximate composition of the atmosphere. In theory we could design and use N2O engines and airplanes etc, and their exhaust could be a gas that is nearly equivalent to atmospheric composition. One important issue is making sure all the N2O has decomposed because it…

Fume events would be more funny, then!

Re: Eliminating contrails from flying could be cheap

#148

Post by Tor3 »

alberth wrote: post #131

I was hoping this was going to be about eliminating the heat trail of a plane. Then learned it’s just about rerouting a flight to climate zones that will less likely form a vapor trail.

But there's no physics which can remove heat from a thermal engine, other than shifting the heat to the outside.

(Science fiction books would use "heat sinks" in their war space ships to try to hide the heat for a short while, but would eventually have to dump the heat somewhere. As heat sinks are basically just a huge mass.. not an option for airplanes.)

Re: Eliminating contrails from flying could be cheap

#149

Post by Tor3 »

ThinkBeat wrote: post #92

Somehow telling airlines to fly what might be quite a bit longer, in order to avoid all the different contrail potenial spot, that will use even more fuel migth nto be a popoular sell?

Due to the current war airplanes from Northern Europe to Asia are already re-routed, increasing travel time from Helsinki to Japan, for example, from previously some 9.5 hours to up to 13.5 hours.

Re: Eliminating contrails from flying could be cheap

#150

Post by joha4270 »

aeternum wrote: post #145
nine_k wrote: post #141

Earlier quoted context omitted.

Does a consumer-grade 8K camera sensor detect a 20°C difference in a few pixels? Cameras have to aggressively fight against thermal noise. Visible light is much more energetic than IR; detecting a faint IR signal with a sensor which is about as hot as the object it's looking at is hard. You need to cool the sensor down; old military aircraft even carried a tank of liquid nitrogen for that. I mean, yes, you can take a…

How many of those attacks were successful? Russia has fairly advanced radar that is quite capable of picking up a plane like that. I think the more likely explanation is that it was incorrectly deemed not a threat or a minor threat. 700 miles is far more than the standard range of the A-20 (210nm). Is it possible they launched it from well within Russia thereby making it much less likely to be considered a threat?

Possible, just like Russel's teapot.

But there has been one very well published Ukrainian attack launched from Russian soil[1].

If Ukraine had could regularly smuggle several drone aircraft's and explosives into Russia and launch them, we would be seeing a lot of other effects. Such as attacks on weapon production sites deep into Russia[2].

But yes, a lot of those attacks are probably unsuccessful. With my qualifications as armchair general, I would be surprised if more than 10% of them was successful.

[1]: https://en.wikipedia.org/wiki/Operation_Spiderweb [2]: https://en.wikipedia.org/wiki/Yelabuga_drone_factory

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