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Aerospace / Re: Lockheed Martin F-35: News ONLY topic
« Last post by SpudmanWP on Today at 03:56:28 pm »
hopefully free of ALL CAPS to show that I am RIGHT and misplaced apostrophe's to demonstrate that you're stupid. {FIFY}

Those who live in glass houses should not throw stones   ::)
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Aerospace / Re: Lockheed Martin F-35: News ONLY topic
« Last post by LowObservable on Today at 03:25:33 pm »
Let me attempt an explanation, hopefully free of ALL CAPS to show that I am RIGHT and misplaced apostrophe's to demonstrate that your stupid.

Low-observable systems invariably combine many different elements because there are different phenomena in the EM spectrum that can cause detection.

Clearly, you start with shape:  avoid 90 degree corners, avoid constant-radius curves aimed at the radar, and align edges and canted surfaces.

All edges have a signature. Point them at a harmless angle or treat with RAM/RAS (wings and tails in particular get RAS). All absorbers are graduated from outside to inside.

Gaps and steps have a signature. Eliminate (for example, with a single-piece skin or continuous coating); align (saw-tooth doors and joints); fill (putties/gaskets).

Surface currents are the mischief. Do not trip them up. Counter-intuitively (to some) the underlying skin must be smoothly conductive, which may require gap and door-edge treatments.

Don't forget IR, although this is usually dealt with by a topcoat, which is not a registered trademark of Lockheed Martin*. (Just make sure the topcoat doesn't goon up the stuff underneath.)

All of this was discussed publicly in the early 90s. It's extremely complex because a problem in one area can affect others. The ballyhooed baked-in elements of the F-35 skin cover only one of the functions of an LO system. They have certainly tried to accomplish many functions over much of the skin with a single hard-setting sprayed-on coat.

If they have achieved near-zero-maintenance LO, good on them. However...

* Maybe the F-35 achieves stealth through the use of auto cleaning products....
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Inspired and referencing Jules Verne's Nautilus. Some interesting design features, but frivolous use of space in keeping with mega-yacht theme. In my head there'ds a smaller 70 meter version, possibly with gas turbine instead of the diesel generators. http://www.hisutton.com/Nautilus-2020_Luxury_Submarine.html
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Postwar Aircraft Projects / Re: CAC Postwar Projects
« Last post by Flying Sorcerer on Today at 01:57:48 pm »
Anyone have any esimated performance specs for the CA-23?
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Aerospace / Re: Lockheed Martin F-35: News ONLY topic
« Last post by SpudmanWP on Today at 01:46:37 pm »
Respectfully disagree.

That's ok.. I will try and comb through the last 15+ years of memories and dig up the specific references that say "why" there are multiple layers and their importance.

In the meantime, the basics are this:

On the F-22, all stealth layers were sprayed on.  They specifically had an issue with the 1st layer that was in direct contact with the skin (metal or composite).  IIRC That first layer had a problem with adhesion to the skin.  If that layer had an issue, then ALL the layers in the area had to be removed and reapplied, in order, with time in between to dry.  This process was obviously was not only time consuming, but also very expensive.

In the F-35 there are basically only two layers, the "baked in" ones that are part of the structure (and cannot thereby "peel off") and the sprayed on "final finish" that also contains the paint and TopCoat®.  This "Final Finish" may scratch but does not peel.  Even if scratched, the effect is negligible.

Here is a quote from the coatings test center where they basically made a doormat of the stuff, walked on it every day, and it was just fine.

Quote
SLD: In entering the facility, I noticed you have a “door mat” of stealth that’s been there for some time.  Can you comment on this “door mat?”

Bill Grant: Oh, the slab of stealth?  That’s our welcome mat.  Yes, we actually have one of the test panels that we use for assessing the stealth of the various materials.  It represents a stack-up that’s consistent with the upper surface or the outer surface of the jet.  It has the exact same structure and the primer and the topcoat system that you’ll find on the operational jets.  And that gets walked upon every time somebody comes in or out of our lab area out there, the repair development center.
Occasionally, we take it up to test to see if there’s any electrical or mechanical degradation to the system and with around 25,000 steps across that system we have not seen any degradation whatsoever.  So we have a great deal of confidence, however anecdotal that may be, that we have a very robust system.

The article as a whole is a good read on the F-35's stealth robustness.

https://web.archive.org/web/20150715003916/http://www.sldinfo.com/the-f-35-low-observable-repair-facility-a-unique-asset-for-21st-century-combat-aviation/


One final thing to keep in mind is that there are basically three kinds of "stealth" on the F-35: The baked in and sprayed on coatings, the "rubber" seals around doors that open during normal ops (gear, canopy, weapon bays, etc), and replaceable items like "putty" and "tape" that are used on panels that are opened infrequently (engine swaps, other access panels, etc).  The issue that the original claim came from may very well come from one of these other items and have nothing to do with the skin/coatings part of the F-35.
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Aerospace / Re: Lockheed Martin F-35: News ONLY topic
« Last post by kcran567 on Today at 01:26:55 pm »
...
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Aerospace / Re: Lockheed Martin F-35: News ONLY topic
« Last post by kcran567 on Today at 01:18:04 pm »
Yes i get the point...

As a previous post suggested, even with multiple scratches the F-35 will not become an B-52 sized radar reflector.

Size and shaping very important as well as coating effectiveness.

 Re: size, isn't the F-5/T-38 relatively stealthy based on their small size? So how much "detectable" on radar would an F-35 be with degraded stealth coatings (from wear or weather etc.)-if it would even be an issue? or is that classified?

The Su-57 might not be as "stealthy" as an F-35, but it does improve on earlier designs and is overall much more effort of "Low Observable" in consideration.
The Russians being wary of stealth as the primary driver in design while taking an approach that does not compromise other aspects. The Su-57 being designed as "counter stealth" to aircraft like the F-22/35. Side mounted and beaming techniques etc.

Sorry if straying off F-35 news, am asking in relation to F-35 surface scratches and coatings issues.
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Aerospace / Re: Space Ship II, White Knight II - projects, flights, info
« Last post by sferrin on Today at 12:49:04 pm »
What a stupid answer, nice from you. I was just reminding that Branson grossly overpromised over the years, 12 years or more. "We will fly in 2007". Yeah, sure dude.

You sounds upset that he didn't quit like everybody else.
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