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China has a stealth fighter plane, and various people are expostulating over it. The meme in the last couple of days is that the Chinese stole the technology from an F-117 that went down over Serbia. It’s getting most attention in the destrosphere; the few sinistropherians who have noted it are pooh-poohing the development and the concern.

Guys, guys. One of the reasons you/we have trouble dealing with the leftoids is that the problem with their ideas and ideals are so often correct at the root; it’s just that extending them is generally an exercise in reductio ad absurdum. It’s not that the J-20 isn’t a threat; it is. It’s overblowing the threat and assuming that the only way the durn Chinks could have come up with it is to steal it that’s ridiculous, a reductio ad absurdum from the other direction.

One of the more entertaining Rocky & Bullwinkle sequences is the “Banana Plot”, in which a scientist has invented the Hush-A-Boom, an explosive that destroys things without making a sound. Our Heroes must deliver the secret to the Proper Authorities, and are pursued by Boris Badenov and Natasha Fatale, who are trying to steal it. Between the pratfalls, it’s an able sendup of the sort of spy fiction that posits a Secret Weapon whose plans must be found and delivered to HQ, or protected from spies. Seek it out and watch it, lest ye re-create the pratfalls in real life.

In the long term there are no technical secrets, no, not even the atomic bomb. The secret of the atomic bomb wasn’t that it was possible, or even how to build it — that could be, and was, derived from the physics. The “secret” was that the United States was rich enough to build the enormous, and enormously expensive, facilities necessary to tease out the details and produce the necessary materials. Keeping a lid on the details was worthwhile, because it slowed the opposition down enough to get ahead, but physics is the same for everybody. People with access to the materials can build an atomic bomb; it’s a hard problem in engineering, but there are lots of good engineers.

Same with “stealth” fighters. (The US military prefers “Low Observable”, which more accurately describes it.) “Stealth” simply means that it’s hard to find it on radar, and takes advantage of the way radar works by controlling reflection. Reflection, as a concept, has been known since Og the cave man admired his visage in a pool of still water, and after some millenia the notion is fairly well understood, by Chinese as well as Americans.

Reflection happens when an electromagnetic wave/pulse/photon hits a surface that conducts electricity at a scale comparable to the energy/wavelength of the incoming energy. The incoming energy creates an electric current, which creates a new electromagnetic wave equal and opposite to the arriving one. Radar sends out a pulse of electromagnetic energy, which is reflected by the airplane and returned to sender; the return pulse is detected, and the detector — receiver — exploits various tricks to tell where the plane is. If you don’t want the radar to “see” the airplane, arrange it so that reflection doesn’t happen, or the reflection is too weak for the receiver to detect, or goes somewhere other than back to the place the pulse came from.

One way to do that is RAM, Radar Absorptive Materials whose surface isn’t particularly reflective but which are partially conductive. The pulse goes in, and instead of creating a new outgoing pulse it is turned into heat that wisps away on the airstream. Two problems: RAM is, for all practical purposes, foam plastic with conductive material inside — the familiar black or pink stuff, used to keep chips from being static zapped, is also RAM. It’s fragile and not very strong, not exactly the stuff you’d really like to make an airplane of! Worse, the whole point of RAM is to let the pulse in and dissipate it, and if it isn’t thick enough for that to happen it’s partly transparent, and the inside of the airplane is full of metal surfaces at right angles.

So the “secret” of the F117 is straightforward, and no secret at all: the outside surfaces are set at angles that tend to reflect the incoming pulse away from the transmitter instead of back to it; those surfaces are made of RAM, which absorbs some of the incoming energy; the inside structure is made at odd angles to avoid corner reflections; and outside structures, like inlets and exhausts for the engine(s), control surfaces, etc., also meet at odd angles, so reflections off those don’t happen or are weakened. And hey, I’ve never even seen an F117, and I can tell you that. To imagine that Chinese scientists couldn’t figure it out is jingoist at best, racist at worst.

Puzzling over bits and pieces of a crashed or shot-down stealth fighter might offer clues as to little bits of technique to accomplish the necessary goals, but the guys at LockMart didn’t think of everything, that I can guarantee. They’d be just as thrilled to get bits and pieces of a J-20, so they could see what the Chinese thought of that they didn’t — and I can guarantee that things like that exist. Don’t give the leftoids ammunition by assuming The Other Guys are stoopid. They aren’t. They can both have the idea in the first place and work out the technical details for themselves, because physics is the same for everybody. Memorizing the formula for Hush-A-Boom, and keeping it away from Boris and Natasha ’til you get it back to headquarters, is likely to be harder than coming up with it in your own lab.

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