Hello gambit.
You seem to be a very knowledgeable engineer to me with experience in the Aerospace Industry. I myself am a young engineer, and have just started my career in the Aerospace industry. I plan on starting my own company eventually, most likely related to the control and electronics side of aviation. Right now i'm working on a multi-sensor turret for L3 Communications WESCAM (here's a link and a video if you're interested:
MX-15 or AN/AAQ-35 ||
Video)
I was wondering the other day, is it possible to have a single UAV produce the exact radiation required to deceive the enemy into thinking an aerial strike package was on its way? I mean, could you make them think that there was a formation of 4-8 aircrafts heading towards a particular point, when in fact it is just a single UAV with a radio transmitter attached to it? The idea seems pretty doable to me, and would be a very convenient way of deceiving an enemy. And once you've got your enemy deceived, he's at your mercy. "The way of the war is the way of deception".
I just thought I'd ask the question. It's been on my mind, and I can't seem to see why it hasn't already been tried. I'd like to know because I am very interested in experimenting with my own UAV designs.
Thanks.
It is good that you are ambitious so here goes...
Currently, RCS reduction techniques are through passive measures such as body shaping
AND materials that absorbs a certain level of energy of the radar signals that impact the body. They are rather loosely called radar absorbing materials (RAM), for lack of better terminologies.
Body shaping are done through basic understanding of radar signal
BEHAVIOR on a body.
The F-117's body shaping and consequently radical RCS reduction was based upon the principle of reflection, that if a planar surface is angled, no matter how slight, any reflection off the surface will be away from source direction as illustrated above.
Now...Because no surface is ever completely smooth, microscopic irregularities create microscopic 'corner reflectors'. Corner reflectors, aka target corner reflectors, are created every time two surfaces or edges meet to create a corner and it is corner reflectors, microscopic or otherwise, that allow detection of the aircraft. Take a walk around the aircraft and it does not take long to recognize corner reflectors all over the body such as where the wing root meet the fuselage, for example.
So first...The aircraft became odd looking with so many angled facets. Then because no surface is ever truly smooth, RAM is installed onto these angled surfaces. The result is that a large part of the radar pulse's energy be reflected away from source direction, then some more energy is absorbed by RAM, then whatever remain of the original pulse that managed to be reflected back to the radar is so weak that the radar will dismiss that echo as 'clutter'. When we get to 'clutter' we are referring to echoes that we
DO NOT want to display. Clutter is arbitrary. For a weapons radar, clouds are garbage but for a weather radar, aircrafts, balloons, birds, buildings, and people are garbage and cloud display are desirable. Clutter also involve constant false alarm processing (CFAR) but that is an entirely different discipline by itself. Clutter and CFAR together is a huge can of worms. Essentially, what we call 'stealth' is the desire to have the enemy think we belong in the 'garbage' region of radar detection and dismiss us until it is too late.
Next to the F-22...
When a radar pulse impact a curved surface, there are some reflections due to microscopic surface irregularities, but then we have the 'creeping wave' phenomenon...
Creeping wave - Wikipedia, the free encyclopedia
Creeping waves greatly extend the ground wave propagation of long wavelength (low frequency) radio. They also cause both of a person's ears to hear a sound, rather than only the ear on the side of the head facing the origin of the sound. In radar ranging, the creeping wave return appears to come from behind the target.
Curved surfaces calculations are much more complex than angled surfaces because the B-2, F-22 and F-35 are not spheres but structurally complex objects. The F-117 was possible even when engineers were using sliderulers. For these aircrafts, their body forms were calculated by supercomputers that simulate nuclear explosions.
So next to a sphere, an
ogive is the next best shape to create electrically long distances for the creeping wave effect and because of the 'creeping wave' effect, the F-22 and its brethens uses far less RAM than the F-117. They need RAM only on the leading edges of the bodies.
Now we come to RAM...
There are:
Resistive
1 - Salisbury screen
2 - Dallenbach layering
3 - Jaumann layering
Inductive-Capacitive
4 - Circuit analog sheeting
The Salisbury screen is the simplest absorber and one that any second rate industrialized country can produce. But it is also the most limited in terms of bandwidth that it can 'absorb'. Then we have increasing sophistication with the Dallenbach and Jaumann layering techniques. To put it simply, each type is essentially a coating, either a solid but flexible sheet or liquid, that contains carbonyl iron or ferrite powders. The problems for the first three types of absorbers are limited bandwidth and with increased bandwidth capability comes the weight penalty. I have no problems telling you this information is because these materials are commercially available -- internal radome coatings. They sort of 'absorb' the transmissions then pass the signals through the radome. You can easily find online information for these three absorbers type.
Item 4 -- circuit analog sheeting -- is the next generation of 'stealth' aircrafts, which will be active RCS manipulators, not merely reducers.
For the first three absorbers, the particles are not uniform in distribution over a specified area. With the circuit analog sheeting technique, precise patterns are created by using multisheeting of the first three absorbers. You can get an idea of the level of complexity by doing some reading on photoetching techniques in semiconductor products manufacturing.
Molecular Expressions: The Silicon Zoo - Velociraptor
Shapes such as triangles, crosses or even stars can be useful. A pattern of these shapes does the same initial function as the ferrite particles in the first three layering techniques, which is to trap the radar signal, but different sizes and shapes gives control over inductance and the spacings between the patterns give control over capacitance. Electrically speaking, it is clearly superior and more flexible than resistive only absorbers.
Here is a small example of some of the things I spoke about...
Frequency tuning characteristics of capacitively loaded Salisbury screen radar absorber
The frequency characteristics of a Salisbury screen radar absorber that incorporates a layer exhibiting both resistive and capacitive properties are considered. If the capacitance is fixed, the absorber thickness and hence weight may be reduced but at the expense of bandwidth. If the capacitance is variable then the absorber may be tuned via an external control signal. The practical limitations of both applications are discussed in relation to recent advances in conducting polymer materials
Inductive-Capacitive techniques are much more complex to manufacture. If you design a supercar with active suspension controls but do not install the computer and sensors that would actually make use of the hardwares, you have just wasted a lot of money for nothing. This mean that corresponding computer and software sophistication
MUST accompany these techniques.
Everything I said so far only scratched the surfaces of radar detection and 'stealth' technologies and very much is the foundation of what you wish to enter. Your questions:
...is it possible to have a single UAV produce the exact radiation required to deceive the enemy...
...when in fact it is just a single UAV with a radio transmitter attached to it?
It's been on my mind, and I can't seem to see why it hasn't already been tried.
Yes...But for a UAV to be successful at such deception, the aircraft must be an active RCS manipulator. As if that is not technically difficult enough, since every design has a unique RCS signature, like a submarine's screw noise, the aircraft must be programmed with the appropriate RCS signature it wishes to emulate to deceive the enemy. This is far more involved that just attaching a 'radio transmitter' and call it good. Naturally, the more RCS signatures programmed, the more flexible the system.
For the UAV...The design must be judicious at using angled facetings at certain areas and curved surfaces at other areas. So just because the F-117 is retired, that does not mean the principle that created the aircraft is obsolete. The panels that are of inductive-capacitive techniques can also be charged, like that of a transistor, and be an emitter, making possible the deception. But what is required from the development side is that you must become an adept
PREDICTOR of how radar signals behave on and off a body, which leads back to all those figures I presented above. If you fly F-15s you must know as accurate as possible the RCS signatures of a clean F-15, an air-air configured F-15 and a ground strike configured F-15. After all, you are trying to convince an adversary that you are sending fighter-bombers from one direction when your forces are preparing to attack from another direction. The ghost fighter-bombers must be convincing. Keep in mind that any radar pulse that reflected off a body make that body an emitter, no matter how fleeting the signal. So why not attempt to control it, not merely mask it like the current techniques using ECM pods?
The US is already on track about making the next generation of 'stealth' aircrafts, manned or un-manned, being active RCS manipulators. The current generation of UAVs are already lethal to a certain degree. The lethality level of future UAVs will be the equal of manned aircrafts, giving the side that wields these weapons system, assuming adequate training, the ability to deceive and confuse its adversary to unprecedented level. The defender must, in very short time and under heavy pressure, decide to whether dispatch his resources to intercept ghosts, ghosts with some weapons, or a full air armada. He does not know. The time to recall his fighters would be the time he is under attack with little or no defense fighters.
This is why the F-117 made the Russians and the Chinese nervous. Neither have an equivalent. Arguments that ask the question about 'reinventing the wheel' misses the crucial point about having valid technical experience upon which progress requires. A country does not have to deploy an operational fleet of F-117 equivalent but for the sake of expertise, at least an indigenous design and at least a few fully flight capable models should exist for R/D purposes and to lay the foundation for the next generation of indigenous designs. You are treading into an area that have so many subcategories and that any of those subcategory can consume an engineer's entire career. I left avionics, particularly flight controls, over a decade ago for family related reasons and currently am in semicon products manufacturing. This is how I learned about how certain photoetching techniques can make possible quickly the next generation of 'stealth' aircrafts. I have given you sufficient leads and keywords upon which you can do your own research so enjoy reading what you find.
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