It’s not just paint but tricky geometry and material choices.
Going over what stealth is, is reduced detection from radar and infrared(effectively heat).
Radar works by throwing signals out and getting the return. If you’re familiar with active sonar and echolocation it’s the same idea. If not, it’s like making ripples in water, and seeing how some of them return to the spot and using that info and a lot of math to determine what is out there.
Infrared checks for heat signatures relative to the background and focuses on that. Hot engines versus a cold background sky.
Radar stealth is all about making sure the radar waves that hit the plane, do not bounce back to the receiver in order for it to detect it.
The paint, which is more like a coating than just a layer of paint has material suspended in it in special ways that do not reflect the waves and instead absorb and trap them. Think like painting something matte black, but for radar waves instead of visual light.
The geometry of the aircraft is a huge thing too. [Right angles, fully flat surfaces, and fully round surfaces are avoided.](https://youtu.be/elIEC6F0x-0?t=188) Right angles act like two mirrors to bounce the signal back, flat surfaces act like one mirror, and round surfaces act like a disco ball where at least one section of the surface will always return to the receiver.
Material choices as well. Hard metal components will give a larger return than a soft composite material like fiberglass where the waves can pass through.
Getting into the weeds a bit more on this.
Technically stealth aircraft can be detectable. They’ll often have extremely small radar returns but still technically detectable. When there are pictures like “this has the radar cross section of a bird” it means that it the equivalent energy returned to the radar is about the same as something with the surface area of a bird. At some distance and if searching the right way, it’s possible to detect but generally it isn’t. There is a lot of random things a radar will detect and selecting for the “We occasionally have a very fast moving very weak return” is extremely hard.
There’s also the unavoidable geometry. At some angles they can be detected if at the perfect angle to find one of the few direct flat spots like the leading edges of wings. Though that’s hard to do with a fast moving aircraft that is also actively avoiding showing that angle to a radar.
Add in electronic warfare where signals are actively being disrupted by jamming and it gets even harder.
Plus when deploying weapons, it adds things like round shapes and right angles which vastly increase the radar return. This is how a stealth bomber was shot down in 1999 over Serbia. Weapons bay was open, and some very creative use of the ground radar systems. Basically at it’s very very lowest setting it could detect that something was there, not a lot of info with it, but just something. Then some luck to catch the aircraft while it was actively dropping weapons.
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