J-10 Thread III (Closed to posting)

[Quickie]

In my opinion, a round surface IS a curved surface. Strictly speaking in the sense of geometry, a round surface is caused by curving a flat surface, thus a curved surface. ALL curved surface can form a circle. The rounder ones form smaller circles while the flatter ones form bigger circles. I think what you have in mind is the actual difference in the magnitude of curvature, which is determined by the radius of the curvature. Bigger the radius, bigger the angle and rounder the object looks.

Imagine a fixed scan angle and a fixed scan distance from 2 scanned objects. One of them a round ball and the other a slightly curved surface. Imagine both of them cover the entire scanned view (or scanned cone in 3D). Then ask the question: Which of the objects has more reflected areas? The answer should be of course the round object, which is also the less stealthy of the two objects.
(There's more to this (like the incident angle) , but let's not drag this on)

Okay. To end the story, I'm just giving the opinion that, stealth-wise and performance wise, there must be a better way of controlling air inlet flow other than DSI (as well as the variable intake). The designers of the F-22 may have already found a way. OTOH, the use of composite (and even radar transparent material) in the DSI, may have already rendered that unnecessary in the near future.

The End.

 

[FriedRiceNSpice]

Okay. To end the story, I'm just giving the opinion that, stealth-wise and performance wise, there must be a better way of controlling air inlet flow other than DSI (as well as the variable intake). The designers of the F-22 may have already found a way. OTOH, the use of composite (and even radar transparent material) in the DSI, may have already rendered that unnecessary in the near future.

The F-22's design is fundamentally different from that of the J-10; it is in a different size class and fills a totally different role than the J-10. Its intakes are optimized for its own design, while the J-10's inlets are more optimized for the J-10. You cannot put Raptor style intakes on a J-10 and expect it to be more stealthy, period. With the chin-mounted intake, a DSI bump is the best way to shield the engine blades from radar waves. If you look at the bottom half of the nose of the F-22, it is shaped very similar to the DSI dome on the J-10. The F-22's intakes are angled sharply so they don't directly need any kind of cone or bump to make it any more stealthy. Just because the Raptor doesn't use DSI does not mean other aircraft would not benefit from it, in regards to stealth as well as performance and weight factors. There is nothing unique about the design of the F-22's intakes apart from the paint and the materials. There is also nothing great about the F-22's intakes apart from its stealth. It does not offer the same high speed performance as either variable-ramp intakes or DSI intakes. If DSI was so unstealthy, why do you think they put it on the F-35? The F-22 was fully complete before the JSF even started windtunnel tests... if its intake was so universailly perfect, then why didn't the JSF incorporate it?

 

[Wolverine]

No, you don't understand. You should expect to see radar waves reflecting back at all angles including those back to the source, although more of the reflected wave energy is concentrated around the angle of incident/reflection. So, for each incident line you draw, there should be infinite reflected lines at all angles, although different in intensities.

Infinite, eh? So the emitter source must be running on an infinitely high power source because typically there's not enough radar waves going around to satisfy your demand of infinity. Clearly the designers of the F-35 think your concerns amounted to squat. And maybe you can reveal exactly which composites are inherently stealthy without an application of RAM on their external surfaces.

 

[Quickie]

Infinite, eh? So the emitter source must be running on an infinitely high power source because typically there's not enough radar waves going around to satisfy your demand of infinity. Clearly the designers of the F-35 think your concerns amounted to squat. And maybe you can reveal exactly which composites are inherently stealthy without an application of RAM on their external surfaces.

You don't seem to understand anything. Are you telling me that you're able to count the number of reflected components, and the word 'many' should be used instead of 'infinite' ? What infinite high power source? Obviously, the total power of the reflected components can never be more than the source signal power.

Look, I'm only giving my opinion that the DSI shouldn't be the last and ultimate solution to controlling inlet air flow. Is that so difficult to accept? Are you telling me the DSI is the stealthiest and the best of all air intakes for all time to come?

I'm not going to reply anymore to your comment on this topic.

 

[latenlazy]

You don't seem to understand anything. Are you telling me that you're able to count the number of reflected components, and the word 'many' should be used instead of 'infinite' ? What infinite high power source? Obviously, the total power of the reflected components can never be more than the source signal power.

Look, I'm only giving my opinion that the DSI shouldn't be the last and ultimate solution to controlling inlet air flow. Is that so difficult to accept? Are you telling me the DSI is the stealthiest and the best of all air intakes for all time to come?

I'm not going to reply anymore to your comment on this topic.

I think the notion that the inlet type itself is a determinate of stealth is a faulty one. Whether it's the best type of inlet to control airflow is a separate matter (from how stealthy it is) and should therefore be evaluated separately. It'd be best not to package the two together.

 

[vesicles]

Imagine a fixed scan angle and a fixed scan distance from 2 scanned objects. One of them a round ball and the other a slightly curved surface. Imagine both of them cover the entire scanned view (or scanned cone in 3D). Then ask the question: Which of the objects has more reflected areas? The answer should be of course the round object, which is also the less stealthy of the two objects.
(There's more to this (like the incident angle) , but let's not drag this on)

OK, this is getting a little ridiculous. The only difference between the two examples you gave is the extend of the curvature. There is no fundamental difference between them. It's only perspective. The one with smaller curvature looks only slightly curved because you stand close by. If you move far away enough, it WILL become a ball.

Example: Compare a basketball and earth. If you stand on the ground, the earth looks flat, or only slightly curved when you stand in an open area. According to your logic, the earth can only be considered a "curved surface". Well, this actually agrees with some people who still think earth is a piece of flat land. SO to them, earth is a curved surface. But is it a piece of flat land or a ball? I hope you say BALL 'cause it IS a ball. Both basketball and earth are balls, one bigger and one smaller. No fundamental difference (shape-wise).

Again, what you are dealing with is the possible correlation betweem the extend of the curvature of a surface and stealth, not a fundamental difference between two distinct geometric shapes.

 

[Quickie]

OK, this is getting a little ridiculous. The only difference between the two examples you gave is the extend of the curvature. There is no fundamental difference between them. It's only perspective. The one with smaller curvature looks only slightly curved because you stand close by. If you move far away enough, it WILL become a ball.

Example: Compare a basketball and earth. If you stand on the ground, the earth looks flat, or only slightly curved when you stand in an open area. According to your logic, the earth can only be considered a "curved surface". Well, this actually agrees with some people who still think earth is a piece of flat land. SO to them, earth is a curved surface. But is it a piece of flat land or a ball? I hope you say BALL 'cause it IS a ball. Both basketball and earth are balls, one bigger and one smaller. No fundamental difference (shape-wise).



Again, what you are dealing with is the possible correlation betweem the extend of the curvature of a surface and stealth, not a fundamental difference between two distinct geometric shapes.

It's actually quite simple. Say you're standing in front of a round window, and a big ball completely covered this window, and it came almost half-way through. Now, try to estimate the area of the surface of the ball that came through the window and call the surface "A". Next, imagine a much bigger ball covering the same round window, and it's so big that only a small part of it came through the window while completely covering it. Again estimate the surface of the ball that came through the window and call that surface "B". Which surface will have the bigger area? The answer should naturally be surface "A". Let's say a radar were to scan the same round window. Which surface will have more area exposed to the radar? The answer is again surface "A" , i.e. the rounder surface, as compared to the slightly curved surface "B".

 

[Wolverine]

You don't seem to understand anything. Are you telling me that you're able to count the number of reflected components, and the word 'many' should be used instead of 'infinite' ? What infinite high power source? Obviously, the total power of the reflected components can never be more than the source signal power.

I'm only quoting from your own words. Don't get mad just because you are now being inconsistent with your claims:

No, you don't understand. You should expect to see radar waves reflecting back at all angles including those back to the source, although more of the reflected wave energy is concentrated around the angle of incident/reflection. So, for each incident line you draw, there should be infinite reflected lines at all angles, although different in intensities.

(my emphasis)

Look, I'm only giving my opinion that the DSI shouldn't be the last and ultimate solution to controlling inlet air flow. Is that so difficult to accept? Are you telling me the DSI is the stealthiest and the best of all air intakes for all time to come?

You are now backtracking from your previous claims that DSI is positively UNSTEALTHY, and based on the responses shutting you down, you have to modify your claims. You probably want to avoid dealing with the fact that the 5th generation stealth aircraft the F-35 has DSI. That's okay. Just admit it.

I'm not going to reply anymore to your comment on this topic.

That's because you recognize you're fighting a losing battle. That's okay, though. I understand.

 

[Engineer]

Infinite, eh?

I think by infinite, he meant reflection in all direction.

As for curvature, what he wanted to say is that an object with bigger curvature would produce a larger specular spot than an object with a smaller curvature. But I don't see how this proves/disproves how DSI has worst stealth characteristics.

 

[Engineer]

It's actually quite simple. Say you're standing in front of a round window, and a big ball completely covered this window, and it came almost half-way through. Now, try to estimate the area of the surface of the ball that came through the window and call the surface "A". Next, imagine a much bigger ball covering the same round window, and it's so big that only a small part of it came through the window while completely covering it. Again estimate the surface of the ball that came through the window and call that surface "B". Which surface will have the bigger area? The answer should naturally be surface "A". Let's say a radar were to scan the same round window. Which surface will have more area exposed to the radar? The answer is again surface "A" , i.e. the rounder surface, as compared to the slightly curved surface "B".

The amount of area exposed to the radar is not equivalent to the amount of signal returned through the window. If you offset both balls so that you are not looking at their center, nothing would return through the window.