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Ok, I don't know if this will be short and sweet or more like a manifesto, but here goes.
Stealth engineers love shapes and hate coatings. They have been trying to make stealth aircraft that don't need coatings but it never works out. Long wavelength RADARs detect big things like aircraft ( even the B-2 can't hide from LW RADAR ) and short wavelength RADARs detect small things like raindrops, bugs, and rivets. Composit structures are somewhat RADAR transparent and allow RF waves to penetrate and find stuff like wires, conduit and fittings before heading back home to the RADAR antenna. Stealth aircraft get a conductive coating over thier composit structures to tie all the surfaces together into one electrically conductive piece, access panels have to have a putty applied and cured to fill a littoral electric gap. This makes all the faceting and shaping work as one big thing rather than all the access panels, doors and various joinery doing thier own individual dance to reflect RADAR. Now you have one big chunk of metal that reflects and deflects the RF energy in a predictable way just like the models did in the lab.
NOW you have to damp that reflected RF energy so it doesn't get back to a RADAR. The U-2, the SR-71 and the F-117 all used the famous "Iron Ball" paint to absorb as much of the RF as possible with that old technology. The B-2 and F-22 use a much more advanced coating but it still is a coating that has to be dealt with. These aircraft even have a mission capable rate ( MCR ) that is skewed depending on the predicted threat vs the current state of it's coatings. For instance a B-2 that has to go bomb some third world trouble spot has a higher MCR because it can carry out that mission even if it has a few nicks and dings in it's stealth armor. If that same plane were to be tasked with penetrating Moskow air defences it's MCR would be VERY low and it would have to put off the mission for a few days as it's coatings got attended to ( I think the original cure time for the B-2 putty was three days or something crazy like that ). They have a portable RCS tester to check it out at any base in the world as well as portable climate controlled hangers to do the curing/testing.
Extra complication, the now perfect 100% stealthy B-2 takes off and heads to Moskow and gets a bird strike or hits a sandstorm. Guess what, yup the coating is damaged, the RCS goes up and depending on how bad the damage is, the mission might be compromised. How would you like to be a Commander dealing with this kind of headache?
Well now here comes the F-35 with a program requirement that it be twice as reliable ( there's that mission capable rate again ) and take half as much time to repair as it's predecessors ( I don't know if "predecessors" means the F-22 or the F-16/Harrier/Hornet ). LockMart originally planned to take care of the coatings problem by doing away with conventional coatings and using a kind of decal/sticker kind of tech to cover the airframe. This had the advantage of being more durable than coatings and would be easier to completely remove when needed. But then around 2004 somebody found something cool, it is now being called "Fiber Mat" and I don't know whether to call it a coating or not.
The F-35 is composed of something in the area of 44% composits, the F-22 was/is about half that.
When you make an aircraft out of composits you have to stick the thing in an oven/mold called an autoclave where it gets baked under pressure until that little pop-up timer thing goes off.
In the F-35s case the mold will first be lined with Fiber Mat, then the parts will go into the autoclave. When it all comes out the Fiber Mat will be fused to the composit and the part will essentially be ready to go NO FURTHER COATINGS OF ANY KIND WILL BE NEEDED FOR RCS if you want the plane to be red or purple or whatever I guess you can still paint right over the Fiber Mat.
Fiber Mat is not just a coating it is a structural part of the shape, it adds strength and support to the underlying composits. If the Fiber Mat gets nicks and dings it is no big deal unless the part is actually damaged.
Think of the plane being kind of like a piece of plastic, the old coatings way would be like having the plastic painted, if you scratch it you can now see the real color of the plastic underneath. Fiber Mat is like having the plastic made with the color already in it, scratch it if you want, but it wont change how it looks until you make a hole in it.
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Fighting for justice with brains of steel
Let your anger be like the monkey which hides inside the piniata.
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