Eliminating contrails from flying could be cheap • Hacker News Board

Re: Eliminating contrails from flying could be cheap

#191

Post by topaz0 » Wed, Oct 08, 2025, 2:58 PM UTC

DoctorOetker wrote: post #186

topaz0 wrote: post #142

Earlier quoted context omitted.

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 st…

You are correct that N2O is the "nitro" afterburner used in different systems. But the reaction 2 N2O => 2 N2 + O2 is very exothermic, in fact it is explosive (but not in the burning sense, since its autodecomposition). However adding a small amount of ethanol makes N2O stable so that sudden shocks or compressions don't result in initiating autodecomposition or explosion. To power an engine one doesn't necessarily ne…

I stand corrected.

Re: Eliminating contrails from flying could be cheap

#192

Post by overfeed » Wed, Oct 08, 2025, 4:14 PM UTC

Tor3 wrote: post #146

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…

"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 hori…

> A typical satellite will orbit once every 100 minutes or so (military spy satellites more often because they fly lower,

Constellations (like Star Shield or the Chinese equivalent) solve this problem; there is always a dozens of satellites overhead, and they don't need a lot of resolving power to detect contrails, I vet even cubesats with repurposed phone-camera sensors would suffice.

Re: Eliminating contrails from flying could be cheap

#193

Post by cyberax » Wed, Oct 08, 2025, 4:56 PM UTC

saagarjha wrote: post #160

cyberax wrote: post #109

Earlier quoted context omitted.

N2O formation enthalpy is just 82kJ/mol. For comparison, water is 240kJ/mol. It doesn't sound so bad, but when translated into grams, it's 1.86kJ/g for N2O and 13.3kJ/g for water. In other words, when burning a gram of hydrogen, you get about 120kJ of energy. When decomposing a gram of N2O, you barely get 2kJ.

You’re off by a factor of 10 somewhere

Nope? A gram of water is mostly oxygen. Hydrogen is just 2/18 of the water mass, so that's where the factor of 9 comes from.

Re: Eliminating contrails from flying could be cheap

#194

Post by aeternum » Wed, Oct 08, 2025, 5:56 PM UTC

nine_k wrote: post #158

aeternum wrote: post #145

Earlier quoted context omitted.

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?

These attacks were so successful that Russia is having fuel shortages right now, and decreased its exports of oil products by about 10%. It is estimated that about 30% of Russia's refining capacity is disabled by now. (E.g. https://www.bbc.com/news/articles/czx020k4056o ) So no, these are not isolated incidents, this is a big hole in air defense, and Russia used to produce some competent air defense systems. They are…

I agree the attacks were successful, I just don't agree they were successful because of lack of detection.

You generally can't continually launch a even $1mil missiles at $100-$10k drones and expect to win. The problem is that most air defenses were designed in an age where the enemy aircraft were quite expensive so it wasn't so critical to optimize ordinance cost. That IMO is the primary challenge for all militaries now.

Re: Eliminating contrails from flying could be cheap

#195

Post by lm28469 » Wed, Oct 08, 2025, 6:25 PM UTC

Den_VR wrote: post #69

aerostable_slug wrote: post #47

Earlier quoted context omitted.

Fun fact: the B-2 bomber has a LIDAR-based contrail detection sensor, called the Pilot Alert System. https://tridsys.com/our-divisions/optical-precision-sensors/

There’s always been something disturbing about public internet advertisements of military equipment. I suppose it’s dual use, but it seems like baiting a malicious actor to play with it in detail.

Wait until you read palantir's marketing. It sounds like your average product owner bullshit but they talk about killing people

https://www.palantir.com/platforms/gotham/

> Gotham's targeting offering supports soldiers with an Al-powered kill chain

> Palantir Gotham is a modern solution for efficient and responsible target management.

> Gotham empowers you to make informed decisions, maximizing the effectiveness of your assets in even the most dynamic operational environments.

> Collaborate across the target lifecycle

Re: Eliminating contrails from flying could be cheap

#196

Post by lm28469 » Wed, Oct 08, 2025, 6:30 PM UTC

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…

> 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

It's not the same IR you'd need for military purposes, you're seeing a tiny percentage of the IR spectrum, and it's the most useless. That's why any semi decent military tier system costs 50k+ a pop. Civilian tier scopes are 1k+ and pretty shit, you won't see anything smaller than a human more than 1km away.

Re: Eliminating contrails from flying could be cheap

#197

Post by asdff » Wed, Oct 08, 2025, 7:13 PM UTC

Agree2468 wrote: post #72

Den_VR wrote: post #69

Earlier quoted context omitted.

There’s always been something disturbing about public internet advertisements of military equipment. I suppose it’s dual use, but it seems like baiting a malicious actor to play with it in detail.

If you're ever in DC, you should check out the ads in the metro stops near the Pentagon. Seeing those kinds of ads in real life is even more shocking.

There is something deeply sinister about seeing a defense contractor building in and around DC. Very nondescript 80s-90s dark plexiglass office box with a parking lot. Only with metal fencing, coated in cameras, anti ram bollards, and an armed guard at the gate, plus no doubt other security measures we can't see. The most secretive cutting edge science on death and killing being performed in the most otherwise happy go lucky seeming 90s model suburbia where there seemingly aren't any poor people around at all. Something deeply dystopian about this model utopia optimized for an ever present and unstoppable war machine.

Re: Eliminating contrails from flying could be cheap

#198

Post by asdff » Wed, Oct 08, 2025, 7:17 PM UTC

tintor wrote: post #137

Den_VR wrote: post #69

Earlier quoted context omitted.

There’s always been something disturbing about public internet advertisements of military equipment. I suppose it’s dual use, but it seems like baiting a malicious actor to play with it in detail.

B-2 is not dual use. There is no civilian use for it.

DOD says we can use thermonuclear bombs for making harbors and other civilian infrastructure so I'm sure there are some "peaceful" bullet points consultants came up with for B-2 as well.

Re: Eliminating contrails from flying could be cheap

#199

Post by [deleted] » Wed, Oct 08, 2025, 9:10 PM UTC

lm28469 wrote: post #195

Den_VR wrote: post #69

Earlier quoted context omitted.

There’s always been something disturbing about public internet advertisements of military equipment. I suppose it’s dual use, but it seems like baiting a malicious actor to play with it in detail.

Wait until you read palantir's marketing. It sounds like your average product owner bullshit but they talk about killing people https://www.palantir.com/platforms/gotham/ > Gotham's targeting offering supports soldiers with an Al-powered kill chain > Palantir Gotham is a modern solution for efficient and responsible target management. > Gotham empowers you to make informed decisions, maximizing the effectiveness of y…

[deleted]

Re: Eliminating contrails from flying could be cheap

#200

Post by nine_k » Wed, Oct 08, 2025, 9:37 PM UTC

aeternum wrote: post #194

nine_k wrote: post #158

Earlier quoted context omitted.

These attacks were so successful that Russia is having fuel shortages right now, and decreased its exports of oil products by about 10%. It is estimated that about 30% of Russia's refining capacity is disabled by now. (E.g. https://www.bbc.com/news/articles/czx020k4056o ) So no, these are not isolated incidents, this is a big hole in air defense, and Russia used to produce some competent air defense systems. They are…

I agree the attacks were successful, I just don't agree they were successful because of lack of detection. You generally can't continually launch a even $1mil missiles at $100-$10k drones and expect to win. The problem is that most air defenses were designed in an age where the enemy aircraft were quite expensive so it wasn't so critical to optimize ordinance cost. That IMO is the primary challenge for all militaries…

You don't need a missile. Any fighter jet is equipped with a cannon; a bunch of 30mm fragmentation-action ammo would dispatch the drone. You don't need a jet; any decent piston-engine trainer plane can fly 4x as fast as the drone, just mount a machine gun on it. Hell, take a civilian helicopter, shoot through the open door. You have ten hours to dispatch it, given that you have detected it.

But, since this is not being done routinely along the way, I conclude that detection fails. All reports about drones shot down mention that the drones were shot down nearby, likely by local air-defense teams near the target. These could as well detect the drone visually, or by the sound.