Stealth Discussion

Skywatcher · Sep 27, 2013

Re: J-20 The New Generation Fighter Thread IV

Engineer said:
Firstly, I have explained in one of my previous posts that in post #1869, your ally expected every single details to be replicated, which would result in a perfect model. Secondly, you are making a big deal out of any deviation in the last few percents of RCS estimation. Anyone who is not expecting perfection will find that small of a deviation as being acceptable.

My ally said that. If you haven't noticed, him (I'm assuming you're referring to a male) and I are different persons.) Sounds like a pretty big misrepresentation (don't think I need to go to OED for that).

The last few percentages (correct syntax) are important in aero-engineering and other high tech, high stakes fields, even for purposes of prediction.

Nope. First of all, your definition has nothing to do with the statement "you can absolutely predict how the other guy's technology will behave". Secondly, your interpretation of the dictionary was entirely opposite to what the dictionary is saying. There is no such requirement of "using the exact same pieces of technology", not even according to the dictionary, as the meaning is entirely your invention.

You used the word "absolute" to declare that you could predict how technology behaves. That means you can predict how the technology can behave "without limit". In order have the limitless "absolute prediction", you will have to have that perfect model that you obsess over.

Firstly, estimating RCS does not require all the fighters to use the same pieces of technologies. We are talking about estimates, not exact values. Second, there exist expertise for China to drawn upon, irrespectively of whether they are spare. What you have brought up here is non-issue.

If you want to understand what the RAM is exactly contribute to the the RCS reduction, you'd better know what that piece of technology is.

If you are wondering where I get the 90% figure from when I said you are portraying Chinese experts as a bunch of amatures, your above post would be it.

I believe it was you who suggested that Chinese engineers could have misunderestimated the RAM effects by 60% (if that post on the J-20 thread hasn't been deleted yet).

Previously, we have learned that 90~95% of the stealth comes from shaping. This puts the remaining 5~10% as effects from RAM. In other words, by assuming there to be a 10% miscalculation in RCS estimation, your thought experiment assumed the Chinese engineers to be so incompetent that their estimations would miss the effects from RAM entirely. Your experiment isn't realistic to begin with. Additionally, there are three other problems.

The effect of RCS reduction is logarithmic, as you pointed out earlier.

So shaping reduces the RCS from 10m2 to 1m2. Then, RAM reduces the 1m2 down to 0.01 m2. But with a 10% miscalculation of the RAM effects, then you get a RCS of about 0.1m2.

That's a tenfold increase!

I am talking about miscalculating the effects of the RAM, not the RCS as a whole. Is that clear, even to you?

First, there is a difference between detection and lock. This was brought up very early on when the scans from a Chinese paper was posted. As opposed to your imagination, your fighter B will not enjoy the advantage of launching any missile right after detection.

That would be true... for Vietnam War era technology.

Thanks to the modern technology of datalinks and midcourse correction, Fighter B can first fire its BVRAAM in the direction of Fighter A. As the BVRAAM goes on its merry way to Fighter A, Fighter B's radar can acquire a reasonably definitive lock on Fighter A and issue corrections to its BVRAAM. Eventually, the BVRAAM will get close enough to Fighter A to pick it up with its own sensors, and Fighter B can go off to attend other tasks.

And Fighter B then will still most likely be the first to establish a lock in any case.

Second, BVRAAM does not have an initial speed of 4900 km/h. The missile has to accelerate, so the actual range traveled by the missile would actually be less than 8 km.

Depends on the BVRAAM, some of the modern ones accelerate very quickly (upwards of 28-30Gs if the manufacturers are to be believed) and go past Mach 4, so Mach 4 is a decent average (we can settle on an initial average of Mach 3.5 if that makes you happy).

Thirdly, a fighter cannot maintain 54km away while presenting the least RCS simultaneously. If Fighter B turns, RCS would not be minimal. If Fighter B maintains its heading, the distance will close rapidly and the engagement will become WVR.

It might interest you to know that not all maneuvering is turning to present a portside view of the aircraft to the opponent. Just a thought.

Fighter B doesn't have to maintain his heading all the way into WVR territory. As soon as the no escape zone of its BVRAAM is great enough, he can break off contact as soon as the BVRAAM can lock onto Fighter A on its own.

Let's say that WVR is about 20km (Wiki has it at 30km, but most WVRAAM don't have that sort of range).

It will take forty seconds for Fighter A and B to get within 20 km of each other (since at Mach 1.5, it will take each Fighter that amount of time to travel 20 km).

But getting WVR for Fighter A is a moot point. Because in that time, the BVRAAM will have traveled 52km at Mach 4.

Engineer · Sep 28, 2013

Re: J-20 The New Generation Fighter Thread IV

Skywatcher said:
My ally said that. If you haven't noticed, him (I'm assuming you're referring to a male) and I are different persons.) Sounds like a pretty big misrepresentation (don't think I need to go to OED for that).

There is no misrepresentation, as I have mentioned you and him together in my posts. An example of misrepresentation is what you are doing here, adding and deleting words in my statement at will in your strawmen arguments.

Skywatcher said:
The last few percentages (correct syntax) are important in aero-engineering and other high tech, high stakes fields, even for purposes of prediction.

The last few percentages may be important in other fields, but we are discussing RCS estimation, not those other fields.

Skywatcher said:
You used the word "absolute" to declare that you could predict how technology behaves. That means you can predict how the technology can behave "without limit". In order have the limitless "absolute prediction", you will have to have that perfect model that you obsess over.

Nope. Your argument doesn't work for three reasons.

First, I didn't just said "absolute" but made a statement which already consists of 11 words before the comma. As "absolute" is just one words, it does not represent my statement.

Second, you are inventing extra meaning to what the dictionary said, just as you are conjuring up extra meanings to what I have said. "Without limit" does not mean perfect model is needed. Such tactic is just another form of misrepresentation, and it isn't going to make your original strawman a valid argument.

Thirdly, "without limit" and "have to have" are opposite in meaning. There is simply no restriction on having a perfect model for RCS estimation, even if the meaning from the dictionary is relevant to what I have said.

Skywatcher said:
If you want to understand what the RAM is exactly contribute to the the RCS reduction, you'd better know what that piece of technology is.

Nope. One does not need to understand exactly what the RAM is contributing to stealth, since the goal is to estimate the stealth fighters' RCS and not the studying of mechanics related to a specific RAM technology. As an analogy, you do not need to understand how photons and electrons interact to produce the color red to know the effect is color red.

Skywatcher said:
I believe it was you who suggested that Chinese engineers could have misunderestimated the RAM effects by 60% (if that post on the J-20 thread hasn't been deleted yet).

What you believed to be what I have said has no relevancy to the examples you have actually said.

Your examples had Chinese engineers getting 10% of the detection range incorrect as a result of miscalculating the RCS. Since 10% is also the contribution of RAM to stealth, your example considered most if not all the effects of RAM to be missing in those engineers' estimation. Hence your example is unrealistic.

Skywatcher said:
The effect of RCS reduction is logarithmic, as you pointed out earlier.

So shaping reduces the RCS from 10m2 to 1m2. Then, RAM reduces the 1m2 down to 0.01 m2. But with a 10% miscalculation of the RAM effects, then you get a RCS of about 0.1m2.

That's a tenfold increase!

I am talking about miscalculating the effects of the RAM, not the RCS as a whole. Is that clear, even to you?

It is clear to me you are not talking about anything that is based in reality. A 10% increase is not the same concept as 10 fold increase.

Skywatcher said:
That would be true... for Vietnam War era technology.

Thanks to the modern technology of datalinks and midcourse correction, Fighter B can first fire its BVRAAM in the direction of Fighter A. As the BVRAAM goes on its merry way to Fighter A, Fighter B's radar can acquire a reasonably definitive lock on Fighter A and issue corrections to its BVRAAM. Eventually, the BVRAAM will get close enough to Fighter A to pick it up with its own sensors, and Fighter B can go off to attend other tasks.

Nope. Detection is not a lock. There wouldn't be any specific direction a missile can be pointed to, because it is a radar lock that gives the directional information.

Skywatcher said:
And Fighter B then will still most likely be the first to establish a lock in any case.

Nope. Detection range and locking range are not necessary correlated.

Skywatcher said:
Depends on the BVRAAM, some of the modern ones accelerate very quickly (upwards of 28-30Gs if the manufacturers are to be believed) and go past Mach 4, so Mach 4 is a decent average (we can settle on an initial average of Mach 3.5 if that makes you happy).

Non sequitur, as it doesn't alter the fact that there is an acceleration which means the missile would not be traveling Mach 4 throughout, making your scenario unrealistic.

Skywatcher said:
It might interest you to know that not all maneuvering is turning to present a portside view of the aircraft to the opponent. Just a thought.

Fighter B doesn't have to maintain his heading all the way into WVR territory. As soon as the no escape zone of its BVRAAM is great enough, he can break off contact as soon as the BVRAAM can lock onto Fighter A on its own.

Let's say that WVR is about 20km (Wiki has it at 30km, but most WVRAAM don't have that sort of range).

It will take forty seconds for Fighter A and B to get within 20 km of each other (since at Mach 1.5, it will take each Fighter that amount of time to travel 20 km).

But getting WVR for Fighter A is a moot point. Because in that time, the BVRAAM will have traveled 52km at Mach 4.

Non sequitur, as not presenting port-side does not mean no maneuvering exist to maintain the RCS to the minimum while simultaneously maintaining about 54 km separation. Your scenario is unrealistic because of such issue. The distance the BVRAAM traveled isn't going to turn an unrealistic point into a realistic one.

latenlazy · Sep 28, 2013

Re: J-20 The New Generation Fighter Thread IV

Skywatcher said:
Not only do you have to look at the various types of RAM, you have to examine how it interacts with the materials used on the aircraft skin.

Which...is why you have hired engineers and super computers.

Skywatcher · Sep 28, 2013

Re: J-20 The New Generation Fighter Thread IV

Engineer said:
There is no misrepresentation, as I have mentioned you and him together in my posts. An example of misrepresentation is what you are doing here, adding and deleting words in my statement at will in your strawmen arguments.

You specifically whined about my perfect model in a post addressed to me. I think it is obvious at this point that he and I are entirely different persons, even to you.

The last few percentages may be important in other fields, but we are discussing RCS estimation, not those other fields.

Nope. Your argument doesn't work for three reasons.

First, I didn't just said "absolute" but made a statement which already consists of 11 words before the comma. As "absolute" is just one words, it does not represent my statement.

Second, you are inventing extra meaning to what the dictionary said, just as you are conjuring up extra meanings to what I have said. "Without limit" does not mean perfect model is needed. Such tactic is just another form of misrepresentation, and it isn't going to make your original strawman a valid argument.

Click to expand...

Without absolute, your statement is just only about predicting how the technology will work. It could be prediction with low confidence, high confidence, medium confidence, etc. Are you a native English speaker?

Thirdly, "without limit" and "have to have" are opposite in meaning. There is simply no restriction on having a perfect model for RCS estimation, even if the meaning from the dictionary is relevant to what I have said.

Click to expand...

"Without limit" means that there are no limitations/caveats on the the model. To have such absolute confidence, you will need that perfect model.

Nope. One does not need to understand exactly what the RAM is contributing to stealth, since the goal is to estimate the stealth fighters' RCS and not the studying of mechanics related to a specific RAM technology. As an analogy, you do not need to understand how photons and electrons interact to produce the color red to know the effect is color red.

Click to expand...

That's a pretty bad analogy.

You DO need to understand how the photons and electrons interact if you want to find that specific type of red (other wise a 1m2 RCS is the same as a 0.05m2 RCS is we applied your analogy to radars).

What you believed to be what I have said has no relevancy to the examples you have actually said.

Click to expand...

Talk about the pot whining.

Your examples had Chinese engineers getting 10% of the detection range incorrect as a result of miscalculating the RCS. Since 10% is also the contribution of RAM to stealth, your example considered most if not all the effects of RAM to be missing in those engineers' estimation. Hence your example is unrealistic.

Click to expand...

Now we can both agree that the effect of RCS reduction on radar detection range is exponential?

So Fighter B has stealth shaping reduce its RCS from 10 meters to 1 meter (that's 90%).

Then, we can only that 1 meter to talk about applying the RAM to.

It is clear to me you are not talking about anything that is based in reality. A 10% increase is not the same concept as 10 fold increase.

Click to expand...

So looking at that 1 square meter, RAM reduces its RCS to 0.01m2.

But getting only 90% of that RAM correct, you get a RCS figure of 0.1m2. Compared to the actual RCS of 0.01m2, the 0.1m2 is a tenfold increase.

Nope. Detection is not a lock. There wouldn't be any specific direction a missile can be pointed to, because it is a radar lock that gives the directional information.

Click to expand...

Detection does give you directional information. Sure, it may be only one point in time, but that's still enough to send the BVRAAM off).

The angular determination of the target is determined by the directivity of the antenna. Directivity, sometimes known as the directive gain, is the ability of the antenna to concentrate the transmitted energy in a particular direction. An antenna with high directivity is also called a directive antenna. By measuring the direction in which the antenna is pointing when the echo is received, both the azimuth and elevation angles from the radar to the object or target can be determined. The accuracy of angular measurement is determined by the directivity, which is a function of the size of the antenna.

Radar units usually work with very high frequencies.

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Click to expand...

Nope. Detection range and locking range are not necessary correlated.

Click to expand...

That may be possible, but not very probable. Logic and physics tells us that if one target has a smaller RCS than the other target, it will be easier to detect. If the two Fighters' radars are of roughly the same technology level, then the radar that has more information to play with (RCS size) will be the first to establish a lock. Can you cite real world examples that show otherwise?

Non sequitur, as it doesn't alter the fact that there is an acceleration which means the missile would not be traveling Mach 4 throughout, making your scenario unrealistic.

Click to expand...

Then what average speed do you suggest we use for the BVRAAM. I've offered the Mach 3.5 figure already.

Non sequitur, as not presenting port-side does not mean no maneuvering exist to maintain the RCS to the minimum while simultaneously maintaining about 54 km separation. Your scenario is unrealistic because of such issue. The distance the BVRAAM traveled isn't going to turn an unrealistic point into a realistic one.

Click to expand...

You're not simultaneously maintaining the 54km separation in the first place.

Engineer · Sep 28, 2013

Re: J-20 The New Generation Fighter Thread IV

Skywatcher said:
You specifically whined about my perfect model in a post addressed to me. I think it is obvious at this point that he and I are entirely different persons, even to you.

You defended his post by responding to me, so you agreed with Inst. You are expecting a perfect model that's not required in reality, or you would have disagreed with Inst and called him out on moving the goal post. Furthermore, in every post of yours since then, you repeated the same requirements for perfection and exactness. The point that Chinese engineers can use their RAM as approximation of F-22's RAM has been raised multiple times. You kept retorting by stating that is not using F-22's materials, so you are not accepting anything other than identical materials used on the F-22. That's expecting a perfect model. So yes, my criticism of you is entirely correct.

Skywatcher said:
Without absolute, your statement is just only about predicting how the technology will work. It could be prediction with low confidence, high confidence, medium confidence, etc. Are you a native English speaker?

My statement has always been about the prediction of how technology works, specifically through application of Laws of Physics. Your obsession over a single word in my statement is no different than the following:
A: I like apples.
B: You used the word like, meaning you have to like oranges as well.

In the analogy, B placed extra meaning into the word "like" that does not exist in the statement of A. B's retort has no relevancy since A never mentioned oranges. Likewise, your conjured up meaning of "absolute" has no relevancy to my actual statement.

Skywatcher said:
"Without limit" means that there are no limitations/caveats on the the model. To have such absolute confidence, you will need that perfect model.

Nope. "Without limit" means one can use anything other than an exact model. When you claim a perfect model must be used, that's placing a limit thus goes opposite to the definition in the dictionary. So the dictionary's definition destroys your own argument. In any case, you are still hung up on the definition of one single word, which does not represent my statement that made up of more than one word. Thus, your definition for absolute is irrelevant.

Skywatcher said:
That's a pretty bad analogy.

You DO need to understand how the photons and electrons interact if you want to find that specific type of red (other wise a 1m2 RCS is the same as a 0.05m2 RCS is we applied your analogy to radars).

Understanding the effect being red is not the same as finding out the specific type of red, so quit your strawman. My analogy remains valid as there is no need to consider how photons and electrons interact to know the effect.

Skywatcher said:
Talk about the pot whining.

Indeed, I have just quoted from a whining pot here.

Skywatcher said:
Now we can both agree that the effect of RCS reduction on radar detection range is exponential?

The effect of RCS reduction on radar detection range is not exponential, but inverse-exponential. Halving the RCS value only reduces the detection range by 1/16th. If you halved the RCS value twice, the second time is not going to give you as much effect as the first time.

Skywatcher said:
So Fighter B has stealth shaping reduce its RCS from 10 meters to 1 meter (that's 90%).

Then, we can only that 1 meter to talk about applying the RAM to.

So looking at that 1 square meter, RAM reduces its RCS to 0.01m2.

But getting only 90% of that RAM correct, you get a RCS figure of 0.1m2. Compared to the actual RCS of 0.01m2, the 0.1m2 is a tenfold increase.

No. Estimating the detection range of a low RCS target is not the same as finding out specific contribution by a specific RAM. Therefore, you cannot just focus on the effects of RAM as you have done above. From 0.1 m[sup]2[/sup] to 0.01 m[sup]2[/sup] is a difference of 0.09 m[sup]2[/sup]. This amount of reduction compared to the original 10 m[sup]2[/sup] without any stealth is only 0.9%!

Skywatcher said:
Detection does give you directional information. Sure, it may be only one point in time, but that's still enough to send the BVRAAM off).

No lock and you are essentially shooting blind. A blind guy can certainly fire a gun, but that doesn't mean it will hit anyone. So my statement still stands in that you are bringing up something in your scenario that isn't realistic to begin with.

Skywatcher said:
That may be possible, but not very probable. Logic and physics tells us that if one target has a smaller RCS than the other target, it will be easier to detect. If the two Fighters' radars are of roughly the same technology level, then the radar that has more information to play with (RCS size) will be the first to establish a lock. Can you cite real world examples that show otherwise?

The issue is that you assumed detection to be a lock when they are different concepts, rendering your scenario unrealistic. Whether a lower RCS target is harder to be locked is a different matter, and doesn't make the unrealistic point a realistic one.

Skywatcher said:
Then what average speed do you suggest we use for the BVRAAM. I've offered the Mach 3.5 figure already.

Fine.

Skywatcher said:
You're not simultaneously maintaining the 54km separation in the first place.

Maintaining more than 54 km separation through maneuvering and the least RCS is no longer presented to the opponent. Maintaining heading means the separation rapidly closes. Either way, the few percentages of RCS effect are nullified, whereas your scenario assumed such tiny difference would be decisively advantageous. Hence, your scenario is unrealistic.

Skywatcher · Sep 29, 2013

Re: J-20 The New Generation Fighter Thread IV

Engineer said:
You defended his post by responding to me, so you agreed with Inst.

I have not asked for perfection and exactness. If I defended Inst, that does not correlate with agreeing with all of his arguments.

You are expecting a perfect model that's not required in reality

And where have I said that? Implications in your imaginations aren't a valid source.

or you would have disagreed with Inst and called him out on moving the goal post.

Furthermore, in every post of yours since then, you repeated the same requirements for perfection and exactness. The point that Chinese engineers can use their RAM as approximation of F-22's RAM has been raised multiple times. You kept retorting by stating that is not using F-22's materials, so you are not accepting anything other than identical materials used on the F-22.

So the Chinese engineers use their own RAM to approximated the F-22's RAM? In that case, why doesn't the Russian military use the T-90's armor to simulate Chobham armor when testing an ATGM? How confident should they be with those results?

That's expecting a perfect model. So yes, my criticism of you is entirely correct.

How close is the Chinese RAM to the F-22 RAM then? Given that the F-22 and F-35, which are both LM products, use completely different RAM, it would stand to reason that the Chinese have their own RAM, unless you think they copied the Americans somehow.

My statement has always been about the prediction of how technology works, specifically through application of Laws of Physics. Your obsession over a single word in my statement is no different than the following:
A: I like apples.
B: You used the word like, meaning you have to like oranges as well.

In the analogy, B placed extra meaning into the word "like" that does not exist in the statement of A. B's retort has no relevancy since A never mentioned oranges. Likewise, your conjured up meaning of "absolute" has no relevancy to my actual statement.

A correct analogy is A: I like ripe apples. Like is a verb, absolute is an adjective. Can we agree on that much, at least?

Nope. "Without limit" means one can use anything other than an exact model. When you claim a perfect model must be used, that's placing a limit thus goes opposite to the definition in the dictionary. So the dictionary's definition destroys your own argument. In any case, you are still hung up on the definition of one single word, which does not represent my statement that made up of more than one word. Thus, your definition for absolute is irrelevant.

Here's the definition:

adverb: with no qualification, restriction, or limitation; totally:she trusted him absolutely

It states with no limitation, "without limit" is "unrestricted":

adjective: not limited or restricted:unrestricted access to both military bases

Understanding the effect being red is not the same as finding out the specific type of red, so quit your strawman. My analogy remains valid as there is no need to consider how photons and electrons interact to know the effect.

In measuring the size of RCS, you have to understand the extent of the effect.

Halving the RCS value only reduces the detection range by 1/16th. If you halved the RCS value twice, the second time is not going to give you as much effect as the first time.

Can I have a source for the halving RCS only reduces the detection range by 1/16?

No. Estimating the detection range of a low RCS target is not the same as finding out specific contribution by a specific RAM. Therefore, you cannot just focus on the effects of RAM as you have done above. From 0.1 m[sup]2[/sup] to 0.01 m[sup]2[/sup] is a difference of 0.09 m[sup]2[/sup]. This amount of reduction compared to the original 10 m[sup]2[/sup] without any stealth is only 0.9%!

Yes, but that that 0.9% does matter!

If you get it 99.7% right, you get 0.03m2, which is a threefold difference. If...

Let's take your "Chinese engineers get within a few percentage points" assertion. With a 3% error, you get a 0.03m2.

Can we agree that a thirty fold miscalculation is a significant error?

No lock and you are essentially shooting blind. A blind guy can certainly fire a gun, but that doesn't mean it will hit anyone. So my statement still stands in that you are bringing up something in your scenario that isn't realistic to begin with.

A more correct analogy is a suddenly light room with a man firing a datalinked, guided bullet. BVRAAMs are guided, after all.

Whether a lower RCS target is harder to be locked is a different matter, and doesn't make the unrealistic point a realistic one.

Since a lower RCS target is harder to be locked onto, Fighter B has time advantage over Fighter A, regardless of whether he (let's take the liberty of assuming both pilots are male) fired upon detection at 60km.

So it will take Fighters A and B 40 seconds at Mach 1.5 to get within visual range (20km) of each other starting from detection at 60km, meaning each fighter has to travel 20 km.

Since Fighter B will only be detected by Fighter A after it has traveled 3km, that gives Fighter A only 34 seconds of situational awareness with Fighter B.

Putting Fighter A at a 15% time disadvantage has very, very negative effects on his OODA loop. Can we agree on that?

Engineer · Sep 29, 2013

Re: J-20 The New Generation Fighter Thread IV

Skywatcher said:
I have not asked for perfection and exactness. If I defended Inst, that does not correlate with agreeing with all of his arguments.

Agreeing with Inst on the use of perfect model does not require you to agree to all of his arguments. I retorted Inst as he expected a perfect replica in RCS estimation through copying and reverse-engineering. You then defend Inst by responding to my specific criticism of him. That already established the logical inference between you and the expectation of a perfect model.

Skywatcher said:
And where have I said that? Implications in your imaginations aren't a valid source.

You have not asked for perfection and exactness, you are expecting it. You are not willing to accept anything unless the Chinese uses the exact RAM that Americans are using. Each time you respond with such expectation, you are only confirming my criticism of you.

Skywatcher said:
So the Chinese engineers use their own RAM to approximated the F-22's RAM? In that case, why doesn't the Russian military use the T-90's armor to simulate Chobham armor when testing an ATGM? How confident should they be with those results?

That's an invalid analogy. Estimating an aircraft's RCS is not the same as measuring exact effects of RAM. Hence your analogy of measuring the exact mechanics of armor is not applicable.

Skywatcher said:
How close is the Chinese RAM to the F-22 RAM then? Given that the F-22 and F-35, which are both LM products, use completely different RAM, it would stand to reason that the Chinese have their own RAM, unless you think they copied the Americans somehow.

Whether F-22, F-35 and J-20 use different RAM is irrelevant.

Skywatcher said:
A correct analogy is A: I like ripe apples. Like is a verb, absolute is an adjective. Can we agree on that much, at least?

"Like" is an English word. "Absolute" is an English word. My analogy is perfectly applicable.

Skywatcher said:
Here's the definition:

It states with no limitation, "without limit" is "unrestricted":

Which is irrelevant to my statement. It does not help your argument either, since "without limit" means there is no limit on using a perfect model. It is simple as that.

Skywatcher said:
In measuring the size of RCS, you have to understand the extent of the effect.

Understanding the effect is not the same as understanding the exact effect. RAM is least significant to stealth, so errors made in estimating the effects of RAM has very tiny effect on the overall RCS estimation. For RCS estimation, there is no requirement for the estimate to be an exact value to the actual one to begin with.

Skywatcher said:
Can I have a source for the halving RCS only reduces the detection range by 1/16?

Sigma is the RCS, where as r is the range. Rearranging the equation to put range on the left hand side, we have a relationship where range is the forth-root of the RCS.

Skywatcher said:
Yes, but that that 0.9% does matter!

It does not.

Skywatcher said:
If you get it 99.7% right, you get 0.03m2, which is a threefold difference. If...

Let's take your "Chinese engineers get within a few percentage points" assertion. With a 3% error, you get a 0.03m2.

Can we agree that a thirty fold miscalculation is a significant error?

It isn't a significant error, because the actual change in radar detection range is tiny. Furthermore, atmospheric effects and hardware imperfection in the radar would cause more change to the detectable range than the last few percentages of RCS estimation.

Skywatcher said:
A more correct analogy is a suddenly light room with a man firing a datalinked, guided bullet. BVRAAMs are guided, after all.

That is not an analogy at all, since there is no such thing as data linked guided bullet. What's more, a room with light suddenly turn on does not represent how a radar works.

Skywatcher said:
Since a lower RCS target is harder to be locked onto, Fighter B has time advantage over Fighter A, regardless of whether he (let's take the liberty of assuming both pilots are male) fired upon detection at 60km.

So it will take Fighters A and B 40 seconds at Mach 1.5 to get within visual range (20km) of each other starting from detection at 60km, meaning each fighter has to travel 20 km.

Since Fighter B will only be detected by Fighter A after it has traveled 3km, that gives Fighter A only 34 seconds of situational awareness with Fighter B.

Putting Fighter A at a 15% time disadvantage has very, very negative effects on his OODA loop. Can we agree on that?

Whether RCS target is harder to locked onto is irrelevant. Anything you are now deriving based on that is also irrelevant. The issue is that you were assuming detection as a lock, which isn't the case in real life. That made your scenario unrealistic. The scenario is also irrelevant in aiding your argument about the last few percentages being important in the estimation.

latenlazy · Sep 30, 2013

Re: J-20 The New Generation Fighter Thread IV

Skywatcher said:
Yes, but that that 0.9% does matter!

If you get it 99.7% right, you get 0.03m2, which is a threefold difference. If...

Uhhhhh...You may want to explain your math. What are you multiplying with 99.7% to get .03 m^2.

Stealth Discussion

Skywatcher

Captain

Engineer

Major

latenlazy

Brigadier

Skywatcher

Captain

Engineer

Major

Skywatcher

Captain

Engineer

Major

latenlazy

Brigadier