Radar Absorbing Materials and Structures (RAM / RAS), stealth (LO) coatings

As I understand it is that Stealth is 80-90% shaping of the plane.You should be able to make a plane out of metal in a specific shape, and it would reflect less then a plane that is not shaped.
IMHO, that only true for full stealth aircraft like B-2, F-117. Whereas, the radar scattering of semi stealth fighter like F-35, Su-57 aren't very impressive.
 

No, RAM does not necessarily behave that way. Thicker is rarely "better". There is an ideal depth for a given material. Modern aircraft often have several stacked layers of RAM that are meant to work together. For example, a low frequency coating that allows higher frequencies through with some attenuation, and below that a high frequency material.
The only reason that I can think of that can possibly make a thinner RAM more effective than thicker RAM layer is the reflection at boundary (before the wave enter the material). So if a metal sheet is placed at 1/4 wavelength distance below that RAM surface then it can prevent front face reflection. But even for X-band, that still need pretty thick layer

The inlets of the F-22 have about a dozen layers of coating.
That would be questionable I think, the full coating these look like 1-2 mm thick at most
 
So thickness in order of Centimeters and differing types of coat can be expected.
 
A "new" coating?

This may yet be a re-discovery. If truly new---maybe a way to give stealth to more conventional airframes?

Space skin
 
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That’s a valid point; how much stealth coating effectiveness gets degraded by dirt and water?
chipped coating or other damage can significantly increase visibility. For a T-75 fighter with a 0.2 m2 RCS or an F-22 with a 0.3 m2 RCS, this is significant
 

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That’s a valid point; how much stealth coating effectiveness gets degraded by dirt and water?
Water/humidity, dirt, and UV all contribute to the degradation of a coating stack. Voids (bubbles) form between layers and then "pop" taking off the coating, etc.
 
Fun fact, the inlet of F-35 and F-22 use some sort of RAM with white color, unlike the outer skin

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That's white paint/topcoat. Though it's probably not using Titanium dioxide as the white pigment.

All jet inlets are painted white at a certain point. (Possible exception for the blackbirds due to heat levels) You need to be able to see anything inside the inlets before starting the engine.
 

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