Eli5: How do stealth boats/planes/submarines hide themselves from radar?
In: Technology
I heard my teacher saying, submarines mimic the sounds of aquatic animals, using vibrations in some way, to hide their presence. Is it true?
Submarines are generally hiding from sonar rather than radar and by coating the submarine in rubber or something similar sound doesn’t bounce off it in the same way that metal does. Planes have two options to defeat radar again they can use a coating which doesn’t reflect radar or they can use various angled surfaces that don’t reflect radar back to the source of transmission but scatter it around.
Radar works by sending out radio waves that pulse out in the air like ripples through water at regular intervals. If one of these waves hits an object, it bounces off in the same way as a ripple does. The radio detector waits to see if a reflection comes back, and then because they know how fast the radio waves are moving they can measure the time it took for the pulse to return and then map out how far away the object is.
Stealth technology focuses on trying to disrupt this process as much as possible. Stealth vehicles are covered with materials and paints that absorb, instead of reflect a lot of the radio waves. Vehicles are also designed to reflect what they can’t absorb at very strange angles, to make sure that as little as possible makes it back to the original site. Some aspects of stealth design are still classified as they are actively used today and cannot be made common knowledge without endangering the vehicles themselves, but these are the things we know.
Unlike in the movies, radar doesn’t show up as little dots on a screen, it’s blurrier than that, and humans are required to interpret the data they see. Stealth designs are not able to make vehicles perfectly invisible, but they can blend in with the background and hope to be missed, mistaken for flocks of birds or waves or smaller ships or even just a glitch or artifact of the radar station. So it’s less like running around with an invisibility cape and more like creeping through the dark when everyone else is making a lot of noise and hoping nobody notices you.
> How do stealth submarines hide themselves from radar?
Can only talk about subs here. Submarine detection isn’t done with RADAR. RADAR is RAdio Detection and Ranging, and radio waves don’t travel well in water.
Instead submarine detection tends to be done with SONAR (SOund NAvgation Ranging). There are two modes to SONAR – active and passive.
Passive: Essentially the detecting ship/boat has very sensitive microphones which listen for noises in the ocean. They try to filter out natural sounds like fish/whales/ground movements. Anything mechanical sounding or rhythmic gets flagged up and reviewed. It’s possible for the systems to identify specific types of ship/boat by the noises they make. As you’re only listening, it’s not possible to detect that someone is listening, but it’s quite difficult to do this well.
Active: The detecting ship/boat sends out a very powerful audio ‘ping’ which is reflected by anything nearby and those reflections are detected by the same equipment. The same as RADAR/LIDAR etc. The big disadvantage with this is that this immediately broadcasts the location of the sender to all boats/ships in the vicinity.
Submarines are coated with special sound-absorbing tiles to try and reduce the amount of noise they broadcast and reflect, all mechanical equipment (such as propellors) is specially tuned to be as quiet as possible, and the crew are trained in how to manoeuvre the boat quietly and efficiently.
By angling all their surfaces rather than having flat, 90 degree facing ones. These deflect the radar waves away from the source rather than back towards them. Dont quote me in this but I also believe there are materials or paints that are designed to absorb these waves
Planes and boats have carefully designed angles to their surfaces, along with special materials, to reduce the reflection of radar waves. Planes also have things like internal missile storage to reduce the surfaces that radar can reflect off.
Submarines are not detected by radar (at least underwater) but sonar. They use similar ideas to reduce reflection, but mainly rely on quiet propulsion systems and sound proofing the interior, to reduce their chances of being heard by hydrophone systems.
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