Eli5: How do stealth boats/planes/submarines hide themselves from radar?
In: Technology
> 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.
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