Shahed drones have increased in altitude from ~500m at the beginning of the Ukraine war to 2000-3000m, which is a 4x reduction in noise on the ground. The higher the drones are, the less noise they make at ground level, and the less effective this ground-based microphone system will be. The drones have moved to elevations to make them more difficult to target with ground based weapons. Reductions in ground noise are a secondary effect.
The latest versions of Shahed can reach 5000m in altitude, which would largely be inaudible on the ground.
At those higher altitudes they are trivial for radar to detect, and from farther away too. They are adapting cheap commodity used marine radars to get this done in some places
I suspect the Shaheds are going higher to mitigate AA ground fire. Higher up you have to send a missile or interceptor up.
And interceptors are more expensive than Shaheds. A $100k interceptor (guessing here) to shoot a $10k Shahed can be an acceptable deal for the side launching the Shaheds.
A $100k interceptor to save a $10 million critical facility against a $10k Shahed is a bargain. You saved $9.9 million dollars.
Interceptor economics makes more sense when you reason about the bigger picture. The point is to buy you time to remove the supply chain and the stocks so that you're not trading 1:1 forever. It's a stop-gap, or at least it's supposed to be.
However that only works in a war where you have air and informational superiority. In a peer-like conflict with information asymmetries and air parity (no way to remove the opponent's industrial base), such as Ukraine-Russia, the intercept economics are less appealing.
With interceptors that cost the defender $100k/unit and shaheds that cost the attacker $10k/unit, over time the attacker can bankrupt the defender if the target is something the defender cannot afford to lose. Sometimes it takes several interceptors to eliminate the threat. Therefore part of the focus in the design of interceptors is to keep their unit cost low.
The unit cost of the first versions of shaheds may have been $10k; more recent models that fly higher, are equipped with a jet engine, more sophisticated electronics, cameras etc. are significantly more expensive. To the point it's not clear to me, of Ukraine or Russia, who pays the higher price during a mass attack at the moment.
Yes, unit costs should be kept as low as possible. My point is that not all wars are wars of attrition with air parity, which is where interceptor economics make the least sense.
Reusable interceptor has BOM of 3000$, 15000$ sales price. Wanted to start this project with an ex-colleague, but he bought old house and is stuck trying to make it livable.
Anyone interested in cooperation? I am hardware and math guy.
Multiple shotgun shells mounted inside of flying platform for final product. For prototyping it is regulatory nightmare in Germany though. That’s a trade-off reusability vs. hard hit. I took Rheinmetall’s calculation of 1000€ for single piece of their magic anti drone munition for business case.
Ukrainian P1-Sun interceptor FPVs were built specifically for this purpose. They are way cheaper than a Shaheed drone and have a practical ceiling of 5000+ meters according to wikipedia.
It's not about "can reach", it's fairly easy to get them to fly even higher. It's about danger of interceptors vs danger of detection. Today's Ukrainian detection network (based on radars) is so dense there is no way to hide from it anywhere, anyway, so high altitude wins.
Interceptors are battery powered and their energy budget and thus range suffers if they have to climb high.
Detection is facilitated by radar, low altitude means flying under the radar (due to curvature of the Earth) - except radar network is now so dense, it in practice can't work anymore. So they can fly low or high they will be detected anyway - but flying high reduces interceptor's reach and makes intercept geometry harder, giving them better chances to slip through.
The distance to the horizon at sea level, is 5km, a high flying drone only increases that.
With a 25k range and a 10k ceiling, and a stupid low unit cost it is dead easy to deploy this en mass to protect vital infrastructure and deny lower visibility routes (valleys, places where detection range is short).
They (Ukraine) are heavy users of YOLO (image model) that runs on some very low end hardware (sub .35 watt for the most efficient models) - and have shown it to be effective for terminal guidance.
The US has a budget item for 2027, DAWG (defense autonomous war group) - that requested 54 billion dollars. This is larger than the USMC's entire budget. This is a quite admission (another one) that the US is far behind, and the things that are going on in the Ukraine are, terrifying.
Could you simply use small cheap balloons with microphones to listen in higher altitudes? Or even small drones that carry the microphones with their own engine noise masked out?
Clouds and nighttime are a barrier to visual detection. Even with good effectiveness the conditions needed for that would mean that you have far less than 50% uptime, and your downtime is predictable to your adversary.
A cheap radar takes an order of magnitude less power to run on hardware that is cheaper than an LLM and can see way farther than a camera.
Radar can't effectively see the new low-altitude small fiber optic spool first-person drones that are redefining frontline war.
The solution is going to be multi-modal (optical + audio) and imperfect. The above poster is correct that an ordinary camera with computer vision (not an LLM, of course) is going to be part of the multimodal defense in depth.
Shahed-type one-way attack drones are important to defend against, but not as impactful in terms of frontline body count, given they just slam into a pre-programmed target.
The article and this thread are about shaheed style drones.
As far as I know, stopping fiber optic fpv drones leans more on physical barriers that catch the fiber (eg road nets) rather than trying to detect and destroy the drone. It’s usually too late by the time you can hear or see a drone that size.
> It’s usually too late by the time you can hear or see a drone that size.
What does the asymptote looks like as defender and aggressor keep iterating. Who has the advantage? Can optical technology get so good at detecting (at least when it isn't raining) that eventually the balance shifts in favor of the defender?
Language models are terrible at computer vision. I don't know why you think that a software to generate words would be able to see flying objects in a picture.
Or it is a public stunt? I am naysayer engineer. Build acoustic detection system for anomaly detection in manufacturing line. It worked with studio level equipment with lots of noise filtering measures. First challenge was to have microphone listening to the right place and getting reliable signal. Second challenge was to amplify the right signal to a level where the features could be extracted. I doubt an old android with dirty microphone can detect anything reliably.
If these Shahed drones have a propeller they should have a brutal signature between 0-250Hz as they are moving a lot of air. And if the engine speed of the Shahed stays constant it will be even easier to detect it ("Angry lawnmower sound".. but that's only the high frequency part of it).
There are extremely sensitive differential pressure sensors (like SDP600-25Pa) available from Sensirion that aren't overly expensive.
Use one differential side and connect it to a kitchen funnel for directional listening the other one to a plastic bottle with a tiny hole in it. This way the sensor will "Null" out the environmental pressure (which the bottle follows very very slowly) from both inputs. It then only will pick up everything high frequency which is left over (and the bottle cannot follow because of its small hole).
This way I was able to detect washing machines that have a physical link to a house from many hundred meters (machine spinning -> house wall shaking -> pressure waves) away. The speed pattern of washing machines when spinning is very unique (several steps over many seconds).
Add this with some GPS PPS frame timestamping and you should have a nice tracking network that doesn't require a lot of bandwidth. But maybe the setup must switch to analog differential pressure sensors as these Senirion-I2C sensors do not have a Sync ping for super precise timestamping.
> Use one differential side and connect it to a kitchen funnel for directional listening the other one to a plastic bottle with a very very small hole in it. It will pick up everything high frequency that's different to the environmental pressure.
Nevermind drones, and war, that's all fine; but I need to know more about this. Is there a phrase or name for this I could use to find more information, maybe example schematics?
Interesting! There are a lot of super loud cars in my urban area. I want to catalog where and when they drive, so I can stand on the side of the street and shake my cane at them.
I’ve always dreamt of building a mesh network of loud vehicle detectors that would map current loud noises and track where loud vehicles live, coupled with very powerful parametric speakers. So when e.g. the network detects a loud motorcycle at 3am anywhere in town, that live sound is instantly played at high volumes targeting only homes where other loud vehicles live.
Somehow there has been little VC interest in this idea.
The equivalent noise density of the sdp600 is 10^-2 Pa/sqrt(Hz). While the noise density of a typical microphone is 10^-6 Pa/sqrt(Hz). At same 50hz low frequencies. So either you're full of shit and a high quality microphone is x10000 more sensitive than this sdp600 sensor, or I'm not understanding what you're saying.
Any self-respecting microphone will be sensitive to tens of micropascals (the conversion between SPL and Pa is straightforward). The Sensirion device is proud of its ability to operate at 10 Pa.
That being said, most microphones are intended for audio and their amplifiers and readout circuitry are not optimized for very low frequencies. And the physical measurement devices don’t work down to DC. (If they did then the microphone wouldn’t work — the DC pressure is around 1 atm, which is some 12 orders of magnitude above the more quiet sounds the microphone is trying to detect.)
A device sold as a pressure sensor will be intended for use at or near 0 Hz and will work fine.
I assume the actual practical crossover is something like 0.1 - 10 Hz depending on the microphone. There’s an additional practical issue, though: the pressure sensor comes from the factory already calibrated for DC, whereas you may be on your own trying to get physical units out of a microphone much below 20Hz.
If you use a high end microphone intended for professional use with phantom power, you will also be fighting the power circuit and lower frequencies.
To detect something, you at least need response that isn’t effectively zero at the relevant frequency. And bonus points for not having ludicrous amounts of jitter due to polling a sensor over a bus like I2C that is really not intended to collect high frequency, equally spaced samples.
It "looked good" for me up to 100Hz after Nyquist in the spectrum but didn't pull any precise data. Just created a 50Hz tone using my speakers which showed up in the spectrum afterwards as expected as basic verification
Took some spectras from heat pumps, airplanes and a helicopter.
A long time ago I used a hot wire anemometer to measure flow up to several hundred Hz, but that was an expensive instrument being read by an expensive National Instruments acquisition platform. This is a cheap, self-contained device. Go Sensirion.
I wonder whether the frequency limit ends up being set by the ADC or the physical sensor. I’m also curious how the Sensirion sensor detects the sign of the pressure difference.
Yes. But they usually are not performing very good between 1-250Hz.
Sensirion is using a thermal flow-sensing principle method which is basically a heated plate that cools/heats up when air passes it - making it extremely sensitive in this range.
The SDP600-25Pa speaks I2C and only has a handful of commands.
Just read it out with a microcontroller you love (like ESP32) and send the samples to a host for analysis. The ESP32 has limited I2C time stretching capabilities limiting it in the highest resolution modes of the sensor - but often that's not a big factor.
To not overwhelm the poor processor and Wifi maybe better a bunch of frames (like 512 or more).
Theoretically wind can be Nulled with a 4-way water splitter that are placed in 90° angles (+ a connector at the bottom to the sensor). As long they are orthogonal the wind pressure coming from one side will cause a negative pressure on the opposite.
Only pressure waves coming into all holes at the same time will reach sensor.
Never tested it. Only a Gedankenexperiment as Einstein would say.
Nothing, but what's the value when it's trivial to filter it away based on known good actors? There will be a frontline somewhere, if suddenly it's reporting drones on the other end of the country, and you know there is no good nodes there, you ignore it.
I remember seeing this on HN when it was first submitted. I honestly think that project is either a scam, an elaborate hoax, a cover for a Chinese company selling radar systems or a three-letter-agency honeypot.
The files [1], [2], [3] on Github (once featured on README and on some articles) depict what I presume is a Chinese built radar which you can see here [4], [5]. I also suspect this might be a honeypot since Instagram - of all places - is full of accounts offering these radars [6], [7]. Some of the contributors on that projects are heavily leaning into AI. Git project history is suspicious. Discussions on the issues seem very artificial. I remember having bunch of notes on this project, but can't find it now. Just looking at it from outside, nothing about it seems real.
While you may be correct in some of these assumptions, the repo is open source, contains actual schematics and code, appears to have real community contributions, and also happens to exists now, which is something that can't be said for the original post this was a response to. I was hoping to just provide some reference to existing work that I found interesting since it is what I think is a much more traditional type of detection system.
I believe Ukrainians had already deployed such a system. This is specifically designed to use old Android phones already sitting in a drawer somewhere without any other use, and most importantly by anyone without technical skills.
Sounds like a simple app with mic input being sent to a yamnet-like audio classification model for a single target detection. Hardly anything innovative?
Multi billion dollar spend to “see” $2,000 aircraft and try to shoot it down with multi million dollar equipment.
The speed to produce and cost effectiveness of these drones are seemingly at a massive advantage right now vs Defense capabilities and straight up cost and looks to be that way for a good while.
> Defense capabilities and straight up cost and looks to be that way for a good while.
You are correct, that today, we (USA) lack the capability to defend against this threat in a meaningful way.
> Multi billion dollar spend to “see” $2,000 aircraft
Look at how we deploy SOCOM assets today: smaller teams in the field far from fixed detection, a satellite to do this job, allows it to be tasked rather than having to deploy more, fixed detection equipment.
As part of a larger system it would be integrated by software: see the "Lattice" project from Anduril.
> and try to shoot it down with multi million dollar equipment.
DAWG, (Defense Autonomous Warfare Group ) has requested a billion dollar base budget and 54 billion of flexible spending (More than the USMC per year) for 2027.
There is also the "Replicator" program (I think headed for phase two) to get unit costs back down, and volume up. Facets of this are bleeding into other spend. Andurill openly talks about unit costs, and how few tools are needed to put together their low cost missiles (still more expensive than drones but... headed in the right direction).
As for the astronomical size of that budget: it's cheap to build an idea, what is hard is testing. The Ukrainians have a massive advantage here, in that they ship these things to the front line. It's much cheaper to trial things when you don't have to buy something to blow up, repeatedly.
The US military has been falling behind for 25 years now (especially the navy: if you want to understand why it has become schrodinger's straight read this https://en.wikipedia.org/wiki/Millennium_Challenge_2002 ) and I think what is going on in Ukraine has been eye opening for them.
Shahed drones have increased in altitude from ~500m at the beginning of the Ukraine war to 2000-3000m, which is a 4x reduction in noise on the ground. The higher the drones are, the less noise they make at ground level, and the less effective this ground-based microphone system will be. The drones have moved to elevations to make them more difficult to target with ground based weapons. Reductions in ground noise are a secondary effect.
The latest versions of Shahed can reach 5000m in altitude, which would largely be inaudible on the ground.
At those higher altitudes they are trivial for radar to detect, and from farther away too. They are adapting cheap commodity used marine radars to get this done in some places
I suspect the Shaheds are going higher to mitigate AA ground fire. Higher up you have to send a missile or interceptor up.
It’s a trade off.
And interceptors are more expensive than Shaheds. A $100k interceptor (guessing here) to shoot a $10k Shahed can be an acceptable deal for the side launching the Shaheds.
Interceptor in this case refers to reusable aircraft. They are sending up cheap to operate prop planes to intercept Shaheds in Ukraine now.
Sending up a plane that costs $500/hour to operate to take down a few Shaheds an hour works out really well.
YouTube has plenty of videos of these guys going up and just shooting them out of the air.
A $100k interceptor to save a $10 million critical facility against a $10k Shahed is a bargain. You saved $9.9 million dollars.
Interceptor economics makes more sense when you reason about the bigger picture. The point is to buy you time to remove the supply chain and the stocks so that you're not trading 1:1 forever. It's a stop-gap, or at least it's supposed to be.
However that only works in a war where you have air and informational superiority. In a peer-like conflict with information asymmetries and air parity (no way to remove the opponent's industrial base), such as Ukraine-Russia, the intercept economics are less appealing.
With interceptors that cost the defender $100k/unit and shaheds that cost the attacker $10k/unit, over time the attacker can bankrupt the defender if the target is something the defender cannot afford to lose. Sometimes it takes several interceptors to eliminate the threat. Therefore part of the focus in the design of interceptors is to keep their unit cost low. The unit cost of the first versions of shaheds may have been $10k; more recent models that fly higher, are equipped with a jet engine, more sophisticated electronics, cameras etc. are significantly more expensive. To the point it's not clear to me, of Ukraine or Russia, who pays the higher price during a mass attack at the moment.
Yes, unit costs should be kept as low as possible. My point is that not all wars are wars of attrition with air parity, which is where interceptor economics make the least sense.
No worries, europe will print money to subsidise ukraine forever.
> A $100k interceptor to save a $10 million critical facility against a $10k Shahed is a bargain. You saved $9.9 million dollars.
Sure until they send 200 Shaheds at a night. Another another 200 next night and so on.
Hence the second paragraph
A $100k interceptor to save a $10 million critical facility against a $10k Shahed is a bargain. You saved $9.9 million dollars.
Your enemy probably isn't sending one drone.
Reusable interceptor has BOM of 3000$, 15000$ sales price. Wanted to start this project with an ex-colleague, but he bought old house and is stuck trying to make it livable.
Anyone interested in cooperation? I am hardware and math guy.
maybe this is a stupid question but how could you possibly re-use a thing that explodes in use
In some cases they are literally flying small prop aircraft and shooting Shaheds down with a rifle from the cockpit, almost like WWI.
I've also seen videos of drones equipped with shotguns shooting down drones, but those seem to mostly be smaller drones, not long range Shahed drones.
In either case, both are examples of re-usable interceptors, manned and unmanned.
Multiple shotgun shells mounted inside of flying platform for final product. For prototyping it is regulatory nightmare in Germany though. That’s a trade-off reusability vs. hard hit. I took Rheinmetall’s calculation of 1000€ for single piece of their magic anti drone munition for business case.
Interceptors can just be an aircraft that goes up and sends a munition at the target.
Think of fighters going up to intercept bombing missions in wwii.
Ukrainian P1-Sun interceptor FPVs were built specifically for this purpose. They are way cheaper than a Shaheed drone and have a practical ceiling of 5000+ meters according to wikipedia.
https://uk.wikipedia.org/wiki/P1-Sun
It's not about "can reach", it's fairly easy to get them to fly even higher. It's about danger of interceptors vs danger of detection. Today's Ukrainian detection network (based on radars) is so dense there is no way to hide from it anywhere, anyway, so high altitude wins.
> It's about danger of interceptors vs danger of detection.
What's with that "vs" trade-off?
You're saying avoiding detection requires high altitudes.
What do interceptors have to do with that?
Interceptors are battery powered and their energy budget and thus range suffers if they have to climb high.
Detection is facilitated by radar, low altitude means flying under the radar (due to curvature of the Earth) - except radar network is now so dense, it in practice can't work anymore. So they can fly low or high they will be detected anyway - but flying high reduces interceptor's reach and makes intercept geometry harder, giving them better chances to slip through.
https://en.wikipedia.org/wiki/Sting_(drone)
The distance to the horizon at sea level, is 5km, a high flying drone only increases that.
With a 25k range and a 10k ceiling, and a stupid low unit cost it is dead easy to deploy this en mass to protect vital infrastructure and deny lower visibility routes (valleys, places where detection range is short).
They (Ukraine) are heavy users of YOLO (image model) that runs on some very low end hardware (sub .35 watt for the most efficient models) - and have shown it to be effective for terminal guidance.
The US has a budget item for 2027, DAWG (defense autonomous war group) - that requested 54 billion dollars. This is larger than the USMC's entire budget. This is a quite admission (another one) that the US is far behind, and the things that are going on in the Ukraine are, terrifying.
> ~500m .. to 2000-3000m, which is a 4x reduction in noise on the ground.
Radiative power drops by the square of the distance? Does anyone with a real physics background start demanding authority on a soapbox like this?
Could you simply use small cheap balloons with microphones to listen in higher altitudes? Or even small drones that carry the microphones with their own engine noise masked out?
Edit: as others say, plain radar will suffice.
So film the sky during charging and run a llm on it?
Or an image detection model. Fraction of the compute and can run even on edge embedded. And easy to train with your own data
Or something like this https://www.youtube.com/watch?v=YZkLQsv3huo
Clouds and nighttime are a barrier to visual detection. Even with good effectiveness the conditions needed for that would mean that you have far less than 50% uptime, and your downtime is predictable to your adversary.
A cheap radar takes an order of magnitude less power to run on hardware that is cheaper than an LLM and can see way farther than a camera.
Radar can't effectively see the new low-altitude small fiber optic spool first-person drones that are redefining frontline war.
The solution is going to be multi-modal (optical + audio) and imperfect. The above poster is correct that an ordinary camera with computer vision (not an LLM, of course) is going to be part of the multimodal defense in depth.
Shahed-type one-way attack drones are important to defend against, but not as impactful in terms of frontline body count, given they just slam into a pre-programmed target.
The article and this thread are about shaheed style drones.
As far as I know, stopping fiber optic fpv drones leans more on physical barriers that catch the fiber (eg road nets) rather than trying to detect and destroy the drone. It’s usually too late by the time you can hear or see a drone that size.
> It’s usually too late by the time you can hear or see a drone that size.
What does the asymptote looks like as defender and aggressor keep iterating. Who has the advantage? Can optical technology get so good at detecting (at least when it isn't raining) that eventually the balance shifts in favor of the defender?
My comment was about Shaheds like the article we are commenting on.
for what you are talking about, audio is a great option
Language models are terrible at computer vision. I don't know why you think that a software to generate words would be able to see flying objects in a picture.
Or it is a public stunt? I am naysayer engineer. Build acoustic detection system for anomaly detection in manufacturing line. It worked with studio level equipment with lots of noise filtering measures. First challenge was to have microphone listening to the right place and getting reliable signal. Second challenge was to amplify the right signal to a level where the features could be extracted. I doubt an old android with dirty microphone can detect anything reliably.
If these Shahed drones have a propeller they should have a brutal signature between 0-250Hz as they are moving a lot of air. And if the engine speed of the Shahed stays constant it will be even easier to detect it ("Angry lawnmower sound".. but that's only the high frequency part of it).
There are extremely sensitive differential pressure sensors (like SDP600-25Pa) available from Sensirion that aren't overly expensive.
Use one differential side and connect it to a kitchen funnel for directional listening the other one to a plastic bottle with a tiny hole in it. This way the sensor will "Null" out the environmental pressure (which the bottle follows very very slowly) from both inputs. It then only will pick up everything high frequency which is left over (and the bottle cannot follow because of its small hole).
This way I was able to detect washing machines that have a physical link to a house from many hundred meters (machine spinning -> house wall shaking -> pressure waves) away. The speed pattern of washing machines when spinning is very unique (several steps over many seconds).
Add this with some GPS PPS frame timestamping and you should have a nice tracking network that doesn't require a lot of bandwidth. But maybe the setup must switch to analog differential pressure sensors as these Senirion-I2C sensors do not have a Sync ping for super precise timestamping.
> Use one differential side and connect it to a kitchen funnel for directional listening the other one to a plastic bottle with a very very small hole in it. It will pick up everything high frequency that's different to the environmental pressure.
Nevermind drones, and war, that's all fine; but I need to know more about this. Is there a phrase or name for this I could use to find more information, maybe example schematics?
The Sensirion SDP600-25Pa speaks I2C and only has a handful of primitive commands. Add this and 3.3V and you are done.
I'm 99.5% sure if you throw Claude with a datasheet on it will Slop out working code for a ESP32 with ESP-IDF.
Someone did something very similar already https://www.holad.de/2023/02/05/Infraschallmikrofon-Messunge...
Interesting! There are a lot of super loud cars in my urban area. I want to catalog where and when they drive, so I can stand on the side of the street and shake my cane at them.
I’ve always dreamt of building a mesh network of loud vehicle detectors that would map current loud noises and track where loud vehicles live, coupled with very powerful parametric speakers. So when e.g. the network detects a loud motorcycle at 3am anywhere in town, that live sound is instantly played at high volumes targeting only homes where other loud vehicles live.
Somehow there has been little VC interest in this idea.
https://freesound.org/people/PicassoCT/sounds/850225/
Curmudgeon Ai?
The equivalent noise density of the sdp600 is 10^-2 Pa/sqrt(Hz). While the noise density of a typical microphone is 10^-6 Pa/sqrt(Hz). At same 50hz low frequencies. So either you're full of shit and a high quality microphone is x10000 more sensitive than this sdp600 sensor, or I'm not understanding what you're saying.
Any self-respecting microphone will be sensitive to tens of micropascals (the conversion between SPL and Pa is straightforward). The Sensirion device is proud of its ability to operate at 10 Pa.
That being said, most microphones are intended for audio and their amplifiers and readout circuitry are not optimized for very low frequencies. And the physical measurement devices don’t work down to DC. (If they did then the microphone wouldn’t work — the DC pressure is around 1 atm, which is some 12 orders of magnitude above the more quiet sounds the microphone is trying to detect.)
A device sold as a pressure sensor will be intended for use at or near 0 Hz and will work fine.
I assume the actual practical crossover is something like 0.1 - 10 Hz depending on the microphone. There’s an additional practical issue, though: the pressure sensor comes from the factory already calibrated for DC, whereas you may be on your own trying to get physical units out of a microphone much below 20Hz.
If you use a high end microphone intended for professional use with phantom power, you will also be fighting the power circuit and lower frequencies.
What’s the frequency response of that sensor? The datasheet says nothing.
Honestly: don't know.
My experiments never had a dependency on linearity.
To detect something, you at least need response that isn’t effectively zero at the relevant frequency. And bonus points for not having ludicrous amounts of jitter due to polling a sensor over a bus like I2C that is really not intended to collect high frequency, equally spaced samples.
It "looked good" for me up to 100Hz after Nyquist in the spectrum but didn't pull any precise data. Just created a 50Hz tone using my speakers which showed up in the spectrum afterwards as expected as basic verification
Took some spectras from heat pumps, airplanes and a helicopter.
So the sensor isn't blind within this range.
Huh, impressive.
A long time ago I used a hot wire anemometer to measure flow up to several hundred Hz, but that was an expensive instrument being read by an expensive National Instruments acquisition platform. This is a cheap, self-contained device. Go Sensirion.
I wonder whether the frequency limit ends up being set by the ADC or the physical sensor. I’m also curious how the Sensirion sensor detects the sign of the pressure difference.
Isn't detecting pressure waves in air exactly what microphones do?
Yes. But they usually are not performing very good between 1-250Hz.
Sensirion is using a thermal flow-sensing principle method which is basically a heated plate that cools/heats up when air passes it - making it extremely sensitive in this range.
Interesting! I will like to see your circuits, if any.
Not much circuits needed.
The SDP600-25Pa speaks I2C and only has a handful of commands.
Just read it out with a microcontroller you love (like ESP32) and send the samples to a host for analysis. The ESP32 has limited I2C time stretching capabilities limiting it in the highest resolution modes of the sensor - but often that's not a big factor.
To not overwhelm the poor processor and Wifi maybe better a bunch of frames (like 512 or more).
Doesn't wind fool this?
Theoretically wind can be Nulled with a 4-way water splitter that are placed in 90° angles (+ a connector at the bottom to the sensor). As long they are orthogonal the wind pressure coming from one side will cause a negative pressure on the opposite.
Only pressure waves coming into all holes at the same time will reach sensor.
Never tested it. Only a Gedankenexperiment as Einstein would say.
Different wind at different altitudes though...
Nice. And instead of smartphones, dedicated sensor using esp32 makes more sense imo.
I wonder how this system can be protected from spam - if anyone can send data there, enemy can, too
I feel like if/once they reach the number of expected participants (10k), it'd be easy to filter out the spam as long as the majority are truthful.
So what prevents enemy from creating 20knparticipants constantly sending fake data?
Nothing, but what's the value when it's trivial to filter it away based on known good actors? There will be a frontline somewhere, if suddenly it's reporting drones on the other end of the country, and you know there is no good nodes there, you ignore it.
For those interested there is an open source radar based phased array project here: https://github.com/NawfalMotii79/PLFM_RADAR
I may have even discovered it from hacker news, I forget now.
I remember seeing this on HN when it was first submitted. I honestly think that project is either a scam, an elaborate hoax, a cover for a Chinese company selling radar systems or a three-letter-agency honeypot.
The files [1], [2], [3] on Github (once featured on README and on some articles) depict what I presume is a Chinese built radar which you can see here [4], [5]. I also suspect this might be a honeypot since Instagram - of all places - is full of accounts offering these radars [6], [7]. Some of the contributors on that projects are heavily leaning into AI. Git project history is suspicious. Discussions on the issues seem very artificial. I remember having bunch of notes on this project, but can't find it now. Just looking at it from outside, nothing about it seems real.
[1] https://github.com/NawfalMotii79/PLFM_RADAR/blob/main/docs/a...
[2] https://github.com/NawfalMotii79/PLFM_RADAR/blob/main/docs/a...
[3] https://github.com/NawfalMotii79/PLFM_RADAR/blob/main/docs/a...
[4] https://www.cloudwalkerfpv.com/product/CW-t20.html
[5] https://www.militarysignaljammer.com/supplier-4701497-survei...
[6] https://www.instagram.com/cloudwalker_radar/
[7] https://www.instagram.com/radar_lisa88/
While you may be correct in some of these assumptions, the repo is open source, contains actual schematics and code, appears to have real community contributions, and also happens to exists now, which is something that can't be said for the original post this was a response to. I was hoping to just provide some reference to existing work that I found interesting since it is what I think is a much more traditional type of detection system.
Wouldn’t a purpose built Esp32 with microphones aimed at the sky do a better job? It would be always on, better directional targeting.
I believe Ukrainians had already deployed such a system. This is specifically designed to use old Android phones already sitting in a drawer somewhere without any other use, and most importantly by anyone without technical skills.
Sounds like a simple app with mic input being sent to a yamnet-like audio classification model for a single target detection. Hardly anything innovative?
AFAIK started by a fellow HN’er
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As much as I like to point and guffaw at "bad evil rocket man" the from orbit bit is doing a massive amount of lift (pun not intended) for that price.
Multi billion dollar spend to “see” $2,000 aircraft and try to shoot it down with multi million dollar equipment. The speed to produce and cost effectiveness of these drones are seemingly at a massive advantage right now vs Defense capabilities and straight up cost and looks to be that way for a good while.
The program will track every aircraft flying on earth simultaneously. The level of scope is not comparable.
> Defense capabilities and straight up cost and looks to be that way for a good while.
You are correct, that today, we (USA) lack the capability to defend against this threat in a meaningful way.
> Multi billion dollar spend to “see” $2,000 aircraft
Look at how we deploy SOCOM assets today: smaller teams in the field far from fixed detection, a satellite to do this job, allows it to be tasked rather than having to deploy more, fixed detection equipment.
As part of a larger system it would be integrated by software: see the "Lattice" project from Anduril.
> and try to shoot it down with multi million dollar equipment.
DAWG, (Defense Autonomous Warfare Group ) has requested a billion dollar base budget and 54 billion of flexible spending (More than the USMC per year) for 2027.
There is also the "Replicator" program (I think headed for phase two) to get unit costs back down, and volume up. Facets of this are bleeding into other spend. Andurill openly talks about unit costs, and how few tools are needed to put together their low cost missiles (still more expensive than drones but... headed in the right direction).
As for the astronomical size of that budget: it's cheap to build an idea, what is hard is testing. The Ukrainians have a massive advantage here, in that they ship these things to the front line. It's much cheaper to trial things when you don't have to buy something to blow up, repeatedly.
The US military has been falling behind for 25 years now (especially the navy: if you want to understand why it has become schrodinger's straight read this https://en.wikipedia.org/wiki/Millennium_Challenge_2002 ) and I think what is going on in Ukraine has been eye opening for them.
Apples != oranges