Stealth Technology Explained!

I read numerous posts here on ATS about the flaws of Stealth Aircraft, and how they don't work as claimed. In all fairness, I think everyone could use a look as how Stealth Technology works. Many of us (myself inculded) often expect the mythical "Invisible Plane". No Aircraft has ever achieve perfect invisibility. As far as we know according to modern Science, this is an Impossible goal. Here's what we have:

Stealth Technology is really about Low Observability (LO), the science of making an object look smaller than it really is.

To Put LO in perspective, let me use an analogy:

Everyone knows that money is NOT invisible, however size affects it obserability.
If you drop a Dollar Bill on the floor, It's easy to spot, even in a room with thick carpet. Now if insead, you drop a dime in the same room with the thick carpet, you might never find it back. Obviously the dime is Not invisible! However, because of it small size it is easily hidden in the thick carpet. You might even be moving it around without being aware of it as you shift throught the carpet looking for it! In this exampe, the dime is like a stealth aircraft: It's not invisible, but it is very hard to find, even if you know what you are looking for!

So how do you make a hugh airplane small enough to be overlooked?

First, realise that radar can (IN THEORY) detect anything. Radar sends out electromagnetic waves that are reflected off the surface of an object. What the radar is looking for is an Echo! When that radar hits an object, an echo is prodused by the radar waves. An antanna at the radar site picks up this echo and sends it to a computer. The computer calculates the direction and strength of the echo and how long it took to come back. Using this information, the radar displays the approxamate size and distance of the object. Now, if the radar displayed Every single Echo of any size or stength, the screen would be too cluttered to be useful. (you'd be picking up dust particles in the air!) The computer sorts through all of the echos and throws out the ones that are too weak to be anything large enough to affect air traffic control (probably around the size of a medium sparrow or robin). These really weak echos (called Noise) are never displayed on the radar.

Now, what does this have to do with a Stealth Plane like the B-2?

Planes like the B-2 are design to deflect most of the Radar that hits them away for the source. They are also covered with a radar absorbing skin or paint, which makes the echo much weaker. This makes a stealth aircraft seem to be so small that it easily get lost among the countless random echos that come back to the radar. The Radar Echo of the Stealth aircraft blends in with the random echos, which are called Noise! The radar sends all of the echos both Aircraft and noise to the computer in the Radar Control Center. The first thing the computer does is seperate useful echos from noise. The "Noise" is throwen out and never recoded, analysed, or displayed. Since the Radar Refection form the Stealth is lost in the Noise, it too is tossed by the computer without being analized or recorded. For this reason, the stealth aircraft never shows up on the radar screen!

That is the basic theory behind Radar stealth. As with everything, the theory doesn't work 100% perfectly in practice. For one reason, The use of deflection means that the RCS isn't uniform. Stealth aircraft are more visible at some angles and less visible at others. Second, the more Radar energy that is directed at an object, the stronger the echo, so the Aircrafts RCS actally increases as it get closer to the radar site. Third, Maintaining a stealthy surface requires careful attention to details. If you miss something, such as a small gap or fastener, the RCS skyrockets.

In addition to the Radar, other things such as Heat, noise, Electronic emissions, and even visual signature can be used to find an aircraft. All of these things need to be addressed to make the plane stealthy!

I hope this explaine Stealth Technology a little better!

Tim

Not to mention Scintillation(glint). Some people wonder that if you have insane computing power you can detect,track, and engage a stealth AC. I don't think so because of scintillation and accuracy not to mention this is the issue with current stealth tech in the future this shouldn't be a problem.

lol, what have you explained????

I don't get it... What was I supposed to have learned that I haven't already?

I hope this thread is aimed at a more newer public and not the one who has discussed the subject thoroughly.

I don't mean to attack you, but your post does seem redundant to me.

Shattered OUT...

Grunt and Shatterred:

SHAME ON YOU!!


Just because you did not learn anything, does not mean the post is of no value. I am certain a search of your little postings would turn up plenty that was common knowledge to somebody else, that mean you should be reprimanded and belittled for it?

Like little kids...


Please, exercise your right NOT to post once and awhile...

Actually I think the post was needed and will be helpful in curtailing infamous posts such as “Fighter X is the best because it’s invisible to radar” or “Yeah right, how can you not spot a bee doing Mach 1?” Good post Tim.

Can we get back to what I was saying beforeand the topic of the thread now. This is for people who misunderstand stealth to learn what's true. Shattered and Grunt you two know better than to criticize people like that especilly when other people would like tolearn more about aviation. So unless you're going to be contributing anything please don't post on this thread.

I agree, there has been a great deal of misunderstanding on the topic, and for forum members who might not have the in-depth practical understanding of radar theory, a summary on the topic is definitely in order. Good work Ghost in trying to deny ignorance, which sadly has been quite evident in a few people who seem to think that one line posts, and making snide comments hinting that they know more, without actually providing any evidence of their supposed knowledge, are acceptable.

For those who are truly interested in the topic, and want to develop a better understanding of the subject, I can recommend George Stimson's Airborne Radar 2nd Edition as a good reference manual. It is pretty expensive, but if you can find it somewhere, it really does provide a lot of detail on the subject, most of it at a level that the average person can understand. It will definitely enhance your ability to contribute meaningfully to discussions on things such as stealth. The link below is not an endorsement of the website selling the book, I have simply picked it because it gives a good overview on the book itself (scroll down for this!). I'm sure you could find it elsewhere as well.

Airborne Radar Second Edition

Wikipaedia also has a number of useful articles on stealth characteristics. The Association of Old Crows AOC is an EW/IO association that some may be interested in.

In short, the EW field is complex. Read what you can, ask questions if you don't know what the hell someone on here is talking about, and try not to get discouraged. It is a fascinating subject (yep, my life is dull) once you get a basic understanding.

Originally posted by skippytjc
Grunt and Shatterred:

SHAME ON YOU!!


Just because you did not learn anything, does not mean the post is of no value. I am certain a search of your little postings would turn up plenty that was common knowledge to somebody else, that mean you should be reprimanded and belittled for it?

Like little kids...


Please, exercise your right NOT to post once and awhile...

I've been here for over 2 years, and I only have about 14000 points made on posts alone. Which means I barely post.

I make like 1-2 posts every two days or so on average.

I do excersice my right not to post, but only because I don't feel it necessary.

I believe I just slapped you across the face.

I never said it was of no value. You automatically assumed that, I just said I didn't learn anything from it. Never dismissed it as a no value post, I wouldn't degrade someone else's post like that by saying it has no value.

After all, I did say I hoped the post was aimed at a more newer audience, meaning it wasn't particularly aimed towards us.

Read carefully, and I did say I didn't mean to make it an attack.

Nothing against ghost personally, he makes good posts, I enjoy learning from many of his posts.

But all I said was that it sounded repetitive to me.

Shattered OUT...

OK, I think I understand basic deflection principle stealth on faceted aircraft, but I am at a loss on how they determine blended stealth.

The diagram below shows two cross-sections of airframe. The upper one is faceted and has two angles ("A" & "B") at which the radar would get a full reflection ("spike")

The bottom one shows the same cross-section but with a fillet along the join of the two surfaces. In my understanding that rounded section would give a wide angle of reflection ("X").

Am I correct?
If someone could explain rounded stealth to me, it would be cool. Thanks.

Originally posted by skippytjc
Grunt and Shatterred:

SHAME ON YOU!!


Just because you did not learn anything, does not mean the post is of no value. I am certain a search of your little postings would turn up plenty that was common knowledge to somebody else, that mean you should be reprimanded and belittled for it?

Like little kids...


Please, exercise your right NOT to post once and awhile...

ohh come on what a tragedy....

well the thread is named "stealth explained" not "how works stealth??" i mean the first post just put all that as facts, not a debate or discussion about that, i already dont have the mod to discuss that, already have disussed some stealth concepts, because isnt so simple like say "is stealth by their computing design" and thats the end of the story, come on..

anyway, try to read a book of EM, or thermodynamics, mother nature have all the answers, i know that this forum have a lot topics about antigravity, UFOs, auroras,conspiract theories, stealth................

btw, planeman, EM waves arent linear -unless their frecuency is infinite, what is impossible-, actually all the radar waves are considered in the low spectrum, and IR, and light is upper, rounded surfaces works to weak the returned signal, by increasing the area inflicted reducing the "density" -intensity- of the retuned signal, it have their pros and contrs, flatenned ones try to change the direction of the signal and throw it to different directions -again if we consider the particle propieties-, like the f117, that use flattened surfaces pointed upwards to avoid the return to ground radars

but again all depends of the frecuency, lower frecuency higher "wave" propiety, higher intensity, higher "particle" propiety

all this even have to do with quantum physics, and the probabylity of absorsion, reflection in "where" will be done, -if it gona do in ram materials or in reflexive ones- and again that depends basically with the frecuency

[edit on 9-5-2006 by grunt2]

Hey Planeman,

I guess (and this is coming from a guy who has only a basic understanding of this stuff) that the curved surface only needs to deflect the energy enough that the receiver doesn't get the return. A one degree deflection against a radar sixty miles away will result in a miss of the antenna by a mile, and given the size of most tracking radars, a little deflection at range will mean the radar deosn't get a return. Even at close range, the miss distance doesn't have to be much. And of course some pretty powerful computers worked out the optimum shapes to reduce cross-section, and as I understand it the B2 simply benefitted from improved processing power by design computers, leading to a blended shape (which I would imagine is of aerodynamic benefit, as well as leading to a low RCS).

Now, this works well for monostatic radars (ones where the transmitter and receiver are the same antenna), but a bistatic system (seperate transmit and receive antenna) has been identified as a possible option for tracking LO aircraft, though I haven't seen anything to indicate that an operational capability exists. Low frequency radars are also believed to have an improved capacity to track LO targets. Of course, tracking and engaging are two different stories.

As I said, the above is based on the thoughts of a fairly simple guy (ie me). Also, check out the following link for more info on stealth. Hope this helps!

Stealth

Planeman, it's my understanding for stealth curvature, is it's not a single curve, but for each, say, degree, the chord length changes. I'd assume if it was for every minute the chord length changes, it would be stealthier.

For example, in a uniform curve, you take two points that are 5 degrees away from each other. Let's say the chord's length is 5cm. If you take two other points on that same curve 5 degrees away from each other, the chord's length would still be 5cm.

It's my understanding that it's continuous curvature for stealth. I.e., take two points 2 degrees away from each other, and the length is 2cm. Now take another two points 2 degrees away from each other on that same continuous curve, and say the length is 3cm.

From that, the chord's length is never uniform, and there never will be a wide area of reflection back to where the radar initiated. That'd be why the F-22A would be expensive to produce. If it's extremely stealthy, I'd say it would have to be a very small number of degrees for each small change in chord length. That'd pose some interesting manufacturing challenges and accuracy.

no Xar you are wrong, the main stealth features that the f22 have isnt these curves, is basically the sharper edges that works as the f117, if you look well the upper sustained curved dont have a big gradient , the f22 curves are aerodynamics, the f23 had concept of the curved -rounded surfaces, -but also had sharped edges- it had a hug wing with a big perimeter to weak the signal, and also had these engines bumps and big oval area to direct upwards and weaken the EM signal and better engine cooling

Willard, curved surfaces dont work so greatelly, because you need a huge area to weak the signal, and that only aplies in X band radar -and the reduction isnt so great-, actually the best shape to that concept is a half flying saucer pointing up, that increase better the area and also have a special tangential effect of the normal compound of the reflection -that if we just consider the particle features, lower band , just dont care -as for the flatnes ones also-, and that have nothing to do if the radar is mono or bipolar

and isnt as you design first stealth and then aerodynamics, first you design a plane to fly, thats the reason why the f23 was a failure


[edit on 9-5-2006 by grunt2]

Most of the sharp (straight?) angles on the aircraft are the ones defining it's shape, i.e. leading and trailing edges and sawtooth for the engines. Looking at a front-on view, you can see the the chord changes in the nose and cockpit due to continuous curvature.

There are parts reminescent of faceted stealth a la F-117, like edges, but most of it's continuous curvature.

Anywho, I was just explaining curved stealth. I'm describing what I see in regards to the Raptor.

[edit on 9/5/06 by Xar Ke Zeth]

Sorry Grunt, you're wrong. The aim is not to weaken the signal with shape. RAM and plasma, and active cancellation, target any energy that may return to the receiver, shape simply deflects the energy as I described.

As for the rest of your post, most of it makes no sense. Not necessarily due to content, but because of basic structure. It is much easier for people to accept what you are saying if they can understand it first.

Xar, i dont denie that the f22 dont have stealth features, but is mostly a f18e overdone, just look where a big percentage of the surfaces are pointing and the edges in the nose arent aerodynamics, the contstant curves that you say are actually aerodynamics progress i mean is like to say that the mig29was designed to be stealth coz looks more rounded than the f4

Willard rounded surfaces weaken the radar by increase of the return area by the higher return surfaced area, maybe you didnt understand it well because as puntual analysis it actually change the direction, but even the signal is returned to the original source, but in a macro analysis, the returned area have a tendency to increase more with the rounded surface, coz the returned radar tranverse area increase constantly weakening the return signal to the puntual receiver



[edit on 9-5-2006 by grunt2]

www.fas.org...

a truelly stealth design, surfaces pointed upwards, a huge perimetre wing, , lack of many internal angles (f22 have many) a small nose, etc, etc,etc

Sorry, once again completely incomprehensible. I didn't understand it because of how you write, not because of the "puntual analysis". Puntual appears to come from Spanish, so if English is your second language, I applaud your efforts at contributing to the discussion, but worry that good points will be missed due to translation issues.

If, however, English is your first language, please take the time and effort to review your post, firstly for spelling, secondly for grammar, and lastly for basic and logical sentence structure. Poorly written posts simply detract from the valuable discussion, as well as confuse the target audience of this thread ie newcomers to stealth technolgy.

I still stick by my posts.

I'm still not sure what you mean.

The YF-23 uses continuous curvature for stealth as far as I can see. It certainly doesn't use the sharp angles of an F-117 to deflect radar.

The curves may be advanced aerodynamic design, but it's characterised by one thing - continuous curvature, which deflects radar. A MiG-29 might have a curved front, but it's not designed with continuous curvature, hence no stealth characteristics.

Basically continuous curvature stealth works like "faceted" stealth with sharp angles, just on a "micro" level. For example, if you draw a 1mm line, and drew another one at a 1 degree angle to it, and did that 90 times, you'd end up with a uniform curve. If you made the lines of varied length, say 1mm, to 1.02mm, increasing 0.02mm each line... all the way up to to 90 lines in a row connected at 1 degree angles, you'll end up with continuous curvature. It would look roughly like how the Raptor's nose is shaped from a side-on view.

Perhaps we should clarify what we're all on about before we start yelling in loud voices the way to beach?