Vanessa1402
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Digging tunnel to fight has been a common tactic since Vietnam war at least. Do modern military have any tactic or system to detect underground tunnel yet?
Is there any sort of sensor that can detect a tunnel?
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Vanessa1402
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How deep can ground penetrating radar go? Like a few meter?
It depends on the moisture contained in the upper layers of the terrain, in the desert geophysical satellites can deepen up to twenty meters in a wadi covered with dry sand. In urban tunnels lined with steel and concrete, this technique is not useful. After an earthquake, rescue teams often use trained dogs to detect carbon dioxide emissions from victims' breathing. High-sensitivity infrared sensors can also be used during cold nights. There are several studies on the military application of these procedures using drones with electronic sensors although I have no data on their actual use in combat situations.
Much further back than that. "Undermining" was a tactic used as far back as the Greeks... you'd tunnel under the walls of the enemy fortification, buttressing the tunnel (and the wall) with wooden supports. And then you'd burn them, the wood supports would collapse, the tunnel would collapse, the walls would collapse.
That sort of tunneling was countered by primitive sensors: ears. Defenders would listen for the sound of people digging away, yards below. And then you'd dig counter tunnels, pouring in water, burning oil or angry men. That system still works... acoustic sensors buried in the ground listen for the sounds & vibrations of underground work being done. That's largely how modern tunnels are detected. Once detected, you can blow them up from above, or drill down into them and fill them with interesting substances.
See:
Tunnel warfare - Wikipedia
The detection by acoustic means requires an absolute silence and total absence of vibrations, it can be useful to rescue victims of avalanches and earthquakes but it is a system that would suffer continuous interference in a scenario of combats with bombings and circulation of heavy vehicles.
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A variety of gravity, magnetic, and hyper spectral sensors were used in airborne surveys over Afghanistan to "detect and map mineral resources" deep below the surface. I can't help but feel that this would also reveal caves and tunnel systems.
According to Dr. John Brozema, head of Marine Physics Branch at the Naval Research Laboratory and chief scientist of Project Rampant Lion (a geophysical survey of Afghanistan), "A gravity sensor detects variations in mass, local mass variations, which could be either density or amount, like a mountain. And so if you take a topographic map and try to remove the topographic variations, you're left with a good estimate of the density variations in the earth beneath you. Magnetic sensors detect the variation in the magnetic field locally. And that tells you about a lot about the minerals or the materials that are in the area. Hyper-spectral imaging [divides the visual spectrum into a wide range of color bands] that are diagnostic of specific [surface] materials."
It's surprising what can be done to eliminate irrelevant sounds with modern tech. Your underground sensor picks up a lot... but a sensor above it picks up a lot of the same stuff, just at different strengths. The differences can be worked out. the more sensors you have, the more you can eliminate sounds that aren't of interest.
If you know, you know...
If you have a fixed border or fortification, as you build your walls you can bury a "fence" of thin wires or optical fibers that penetrates deeply. If the gap between each wire is narrow enough, anyone digging through would have a hell of a hard time avoiding cutting the wires and breaking the connection. A sensor goes out, you have a good idea where a tunnel is.
Tunnel Detectors Ferret Out Enemy Below Ground
On the battlefield, detecting secretive underground tunnels has been a challenge that has been answered by the U.S. Army Engineer Research and Development Center's engineers at the Geotechnical and
www.defense.gov
Vanessa1402
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So sound detector seem like a good ideal if they are digging the tunnel?. Seem like there is not many ways to hide that sound. But what if the tunnel is already finished?.
Sorry, had to.
If the tunnel is inhabited, the sounds will escape through the ventilation holes and can be triangulated with directional microphones. There are computer programs developed for submarine warfare that can select only the acoustic frequencies coming from a given marking. Possibly the most effective countermeasure will be to install random noise emitters, surrounded by bobby traps, in places away from ventilation ducts.
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To be fair, it kinda funny that despite decade of technological development, the modern military still get issue with guerrilla fighter hiding under tunnel they can dig by hand. A 1000 USD tunnel is much harder to find compared to 100 millions USD stealth fighter
Sure, but the tunnel only goes the one place, and a place not that far away. And a stealth fighter is unlikely to be filled with exhaust fumes, napalm, water or raw sewage if discovered.
To be fair, if the tunnel is 300-400 km long like under Gaza, it probably doesn’t matter
400 *kilometers* long? Gonna take a while to fill that with sewage and pig offal...
GPR / SAR / SLAR. Got interested in it because lunar lava tubes. It's a rich and long story. In vietnam the Army had a small, mobile GPR at the back of trucks and jeeps, to find Vietcong tunnels.
NASA and NRO got interestd in it: QUILL, then ALSE - Apollo Lunar Sounder Experiment (Apollo 17). Next: Seasat, and a spare was mounted inside a Shuttle payload bay in 1981 and a few other missions.
The Soviets used it on nuclear radarsats : looking at USN warships from above.
Lot of aircraft got SLAR, one early example was the Phantom APQ-102. Goodyear, Willow Run lab were pioneers. SR-71 had it too, with ground resolution improved in steps, starting from 50 feet.
NASA and NRO got interestd in it: QUILL, then ALSE - Apollo Lunar Sounder Experiment (Apollo 17). Next: Seasat, and a spare was mounted inside a Shuttle payload bay in 1981 and a few other missions.
The Soviets used it on nuclear radarsats : looking at USN warships from above.
Lot of aircraft got SLAR, one early example was the Phantom APQ-102. Goodyear, Willow Run lab were pioneers. SR-71 had it too, with ground resolution improved in steps, starting from 50 feet.
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