Stealth question - Reduction in RCS

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spazsinbad

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Unread post13 Dec 2013, 20:31

Interesting Variation on the Lens with IPP detail in this 'only one lens on top' F-35A photo: http://wpmedia.blogs.ottawacitizen.com/ ... g-copy.jpg

Quote about a different F-35A....

'LMAggie' said: (19 Feb 2008)
"...The dark spot is the exhaust hole and the light colored material surrounding it is a special material developed to withstand the high temps from the IPP and be LO at the same time (which is extremely hard)."

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Unread post15 Dec 2013, 08:21

Why is there only 1 lens on the top side of that aircraft?

Shouldn't there be two lens to provide full spherical EODAS viewing?
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Unread post15 Dec 2013, 08:52

Testing the effect of one lens on top would be one guess. Or they ran out of lens to fit one day? Perhaps there is only one underneath on the opposite side. My guesses go on and on.... BTW these are Luneberg (one spelling) Lens which enhance the Radar Signature of the aircraft - or hide the signature (in effect) of the LO version when they are fitted. In any event as explained on a thread about them they are needed for cross country ATC radar monitoring in the absence of JPALS becoming prevalent for precision landings in any environment. Otherwise precision radars are not able to see them for such approaches today.

Search this F-35 forum with 'Luneberg' will get a few hits that may interest you?
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Unread post15 Dec 2013, 17:07

kamenriderblade wrote:They may not be supportive of China, but it currently is a one party state.
IndoChina, do you support the one party state that currently rules Vietnam, or do you wish for a democratic government to take over Vietnam?


One eyed narrow Australian - "mind your own business". Also the other narrow US type. Why bring nationality or Political leaning into a debate about Planes. [Don't use the excuse he is biased - if he is biased I hate to think what both of you are! Triple biased!]

Lets look at the facts. The Vietnamese did not want the USA or Aus [as there accomplice] there fighting a Proxy War with the USSR killing millions using indiscriminate bombing, using that insidious "Napalm" and knowingly dumping millions of tones of high Dioxin content Agent Orange on there country. [Australia did none of that - we used our own tactics thank God].

Dioxin the worst poison known to man. The US as usual "lying" claimed it was only the equivalent of 245T.[The Commercial Product] Bullshit - all the Dioxin is taken out of 245T. Most was left in Agent Orange. Get off your sanctimonious soapboxes. I would expect better from an Australian. Using Agent Orange in my mind was in my mind a War Crime - very similar to using Chemical Weapons. Just how many Vietnamese have been born deformed etc. since its use and how many poisoned by its after effects etc.

The US and Aus have nothing to be sanctimonious about regarding Vietnam. Communist or not he and his fellow Vietnamese have a lot less to be ashamed of than the USA and Aus who supported a Military Dictatorship in South Vietnam supported by about 5% of the ruling elite and never ever tried to hold the elections they promised and promised to hold for years.

Australian 63 and I lived that era. At least Australia accepted we should never have been there quickly and we established relations with Vietnam quickly and admitted our mistake. Something the US overall has never done. It took a sulking sanctimonious US until the 1990's to even trade or talk to Vietnam.
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Unread post18 Dec 2013, 01:08

On Your Radar 18 Dec 2013 John A. Tirpak
"New fairings have shown up on F-35 fighters; two ogival bumps on the top rear, forward of each vertical fin, and two on the bottom, one either side, just forward of the tailhook housing. Lockheed Martin test pilot Bill Gigliotti told the Daily Report the fairings are radar cross section enhancers, put there so air traffic controllers can see the stealthy F-35s when they fly through civil airspace. The F-22 has a similar device, and the Lockheed F-117 also sported a faceted version on each side of the fuselage. The radar reflectors—sometimes called Luneburg [other spellin'] lenses—are removed when the aircraft is employed in stealth mode."

http://www.airforcemag.com/DRArchive/Pa ... Radar.aspx
&
"New fairings have shown up on F-35 fighters; two ogival bumps on the top rear, forward of each vertical fin, and two on the bottom, one either side, just forward of the tailhook housing. The photo here was taken at Lockheed’s Ft. Worth, Tex., facility on Dec. 13, 2013." Staff photo by John A. Tirpak

http://www.airforcemag.com/DRArchive/Pa ... radar.aspx
&
http://www.airforcemag.com/DRArchive/Pu ... radars.jpg
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Unread post18 Dec 2013, 17:48

New? They have been there since 2010.

Here is AF-03 prior to painting in 2010.
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Unread post18 Dec 2013, 18:04

:D Heheh I think they have been browsing this thread. :D Nice photo with the tower. :D
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Unread post25 Dec 2013, 22:38

popcorn wrote:I was going over the latest edition of "The Radar Game" and noticed two passages that appear to be an inconsistent and not caught by the editors..

"For example, the radar range equation can be used to demonstrate logarithmically that a 40 percent reduction in RCS causes only a 10 percent reduction in the detection range."

"An aircraft that reduces its front?aspect signature by a factor of 10 cuts the notional detection range by 44 percent."

The first passage is the correct one, right?


Boy, did this post take some twisted turns. To the OP, did you get you question answered? Bottom line, both statements are correct (although their math is slightly off). To prove it take the ratio of new RCS to old RCS and take the 1/4 root to get the ratio of range.

Statement 1) reducing signature by 40% means a ratio of 0.6.
0.6^.25 = .88 (new max detect range is 88% or original max detect range)

Statement 2) reducing signature by a factor or ten means a ratio of 0.1.
0.1^.25 = .56 (new max detect range is 56% or original max detect range)
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Unread post26 Dec 2013, 03:23

Roscoe wrote:
popcorn wrote:I was going over the latest edition of "The Radar Game" and noticed two passages that appear to be an inconsistent and not caught by the editors..

"For example, the radar range equation can be used to demonstrate logarithmically that a 40 percent reduction in RCS causes only a 10 percent reduction in the detection range."

"An aircraft that reduces its front?aspect signature by a factor of 10 cuts the notional detection range by 44 percent."

The first passage is the correct one, right?


Boy, did this post take some twisted turns. To the OP, did you get you question answered? Bottom line, both statements are correct (although their math is slightly off). To prove it take the ratio of new RCS to old RCS and take the 1/4 root to get the ratio of range.

Statement 1) reducing signature by 40% means a ratio of 0.6.
0.6^.25 = .88 (new max detect range is 88% or original max detect range)

Statement 2) reducing signature by a factor or ten means a ratio of 0.1.
0.1^.25 = .56 (new max detect range is 56% or original max detect range)



Twists and turns are fine .. thanks for your explanation.
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Unread post29 Jan 2014, 14:34

The Real of RCS specs (Fix):

RCS of the missile would increased RCS of fighter. I use calculus plus: RCS of the aircraft + 1 x hardpoints

For example AIM-9/120 or R-73/77 increased approximately 0,01-0,1-1m2 RCS per pylons and missiles (for size A2A missile).

=>>
F-15A RCS found in the range of 15-20-25m2, would grow RCS up to 30m2 with by the 10 A2A missile (or A2G missile, not including CFTs)
F-15C/E RCS 10-15m2 = 21m2 (hardpoint carry 11 A2A missile, not including CFTs)
J-11A/Su-27SK RCS 10-15m2 = 20m2 ( carry 10 A2A missile)
MiG-29 RCS 5m2 = 11m2 (6 A2A)
MiG-21/F-16A/Mirage 2000 RCS 3m2 = 7-9-12m2 (4-6-9 A2A)
MiG-29K/J-11B RCS 3m2 = 16m2 (13 A2A) / 13m2 (10 A2A)
F/A-18A/B/C/D RCS 3m2 = 12m2 (9 A2A)
Su-30MKK/MKI/MK2 RCS 4m2 = 16m2 (12 A2A)
Su-35S RCS 2-2.5m2 = 16m2 (14 A2A)
F-16C RCS 1.2m2 = 12.2m2 (11 A2A)
F/A-18E/F RCS 1m2 = 12m2 (11 A2A)
Rafale RCS 0.3m2 = 13.3-14.4m2 (14 A2A. Because 14 for Air Force versions (Rafale B/C), 13 for Navy version (Rafale M)
EF-2000 RCS 0.5m2 = 13.5m2 (13 A2A)


To rectify this. The Russians use RAM for R-27 missiles while Americans use enclosed weapons pods for F/A-18E/F

http://www.fighter-planes.com/stealth2.htm
http://www.flightglobal.com/blogs/the-d ... od-mockup/

RAM for R-27 or other missile A2A of Russia, it will increase the weight but not too big, maintaining maneuverability of the aircraft. While the EWP for F/A-18 , it will increase the weight and do not guarantee reduced RCS
Last edited by indochina on 31 Jan 2014, 10:10, edited 4 times in total.
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Unread post29 Jan 2014, 16:16

RAM for russian missiles was only study it wasnt became operational thing.

I heard Israel is doing something similar for Python-V, they want to have externally Python-V for F-35.
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Unread post29 Jan 2014, 19:59

milosh wrote:RAM for russian missiles was only study it wasnt became operational thing.

I heard Israel is doing something similar for Python-V, they want to have externally Python-V for F-35.


ok, but it maybe is a concect ?

EWP for F/A-18 same thing ! it is very hard became reality
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Unread post29 Jan 2014, 20:52

indochina wrote:
milosh wrote:RAM for russian missiles was only study it wasnt became operational thing.

I heard Israel is doing something similar for Python-V, they want to have externally Python-V for F-35.


ok, but it maybe is a concect ?

EWP for F/A-18 same thing ! it is very hard became reality

The F/A-18E/F has RCS reduced pylons in service for a while. The legacy F/A-18 pylons were used operationally at IOC. The canted pylon mounting doesn't really help reduced frontal RCS or transonic drag and should really be straightened, with enhanced ejector racks be used for stores clearance. Compatibility with legacy pylons is what doomed that proposal.

Luckily, the design of the F-35 doesn't have the same pylon clearance issues, so straight RCS-reduced pylons would allow advanced RCS reduced missiles to be effective.
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Unread post30 Jan 2014, 10:33

indochina wrote:The Real of RCS specs:

RCS of the missile would increased RCS of fighter.

For example AIM-9/120 or R-73/77 increased approximately 1m2 RCS per pylons and missiles.

=>>
F-15A RCS found in the range of 15-20-25m2, would grow RCS up to 150m2 with by the 10 A2A missile (or A2G missile, not including CFTs)
F-15C/E RCS 10-15m2 = 110m2 (hardpoint carry 11 A2A missile, not including CFTs)
J-11A/Su-27SK RCS 10-15m2 = 100m2 ( carry 10 A2A missile)
MiG-29 RCS 5m2 = 30m2 (6 A2A)
MiG-21/F-16A/Mirage 2000 RCS 3m2 = 12-18-27m2 (4-6-9 A2A)
MiG-29K/J-11B RCS 3m2 = 39m2 (13 A2A) / 30m2 (10 A2A)
F/A-18A/B/C/D RCS 3m2 = 27m2 (9 A2A)
Su-30MKK/MKI/MK2 RCS 4m2 = 48m2 (12 A2A)
Su-35S RCS 2-2.5m2 = 28m2 (14 A2A)
Rafale RCS 1.4m2 = 18-19.6m2 (14 A2A. Because 14 for Air Force versions (Rafale B/C), 13 for Navy version (Rafale M)
F-16C RCS 1.2m2 = 13.2m2 (11 A2A)
F/A-18E/F 1m2 = 11m2 (11 A2A)
EF-2000 RCS 0.5m2 = 6.5m2 (13 A2A)


To rectify this. The Russians use RAM for R-27 missiles while Americans use enclosed weapons pods for F/A-18E/F

http://www.fighter-planes.com/stealth2.htm
http://www.flightglobal.com/blogs/the-d ... od-mockup/

RAM for R-27 or other missile A2A of Russia, it will increase the weight but not too big, maintaining maneuverability of the aircraft. While the EWP for F/A-18 , it will increase the weight and do not guarantee reduced RCS


What is your source for these claims? I find it very strange that same amount of similar missiles would increase the RCS of F-15 or Su-27 to over 100 m2 and the RCS of Su-35, Rafale or F-16 to only 10-20 m2.

To me, it seems extremely unlikely that an air-to-air missile would have 1 m2 RCS except directly from side where it can be quite a lot larger than that. Even 1 degree off and it's likely to be much lower. Pylons are much the same, they likely have very low RCS, especially if designed with that in mind. Their largest RCS would be directly from side, but much can be done with good RAM treatment (with 15-20 dB lower RCS than without RAM).

There has been pretty good missile RCS experiments done and published, for example: http://www.jatm.com.br/ojs/index.php/jatm/article/viewFile/118/118

This shows Brazilian MAA-1 Piranha missile RCS calculations and experiment results. MAA-1 Piranha is somewhat like AIM-9L/M missile in shape and size. This shows that MAA-1 missile RCS is about 0.01 to 0.1 m2 except directly from behind where it's about 1 m2 and directly from side where it rises to about 50 m2. The result directly from sides is probably because the fins and wings act like corner reflectors. Missiles like AIM-9X, ASRAAM and AMRAAM (especially C- and D-models) have fins and wings that should work much better as they won't act like corner reflectors (due to their positioning, alignment and shape) and the RCS should be less than 1 m2 even from sides. Similarly they should have significantly lower frontal RCS due to much better (for low RCS) nose shape. These missiles also likely have been designed low RCS much more in mind than MAA-1 Piranha. I bet the RCS of F-35 with couple of external AIM-9X, ASRAAM or AMRAAM will be lower than 0.1 m2 frontally and less than 0.5 m2 directly from sides. For Rafale or Eurofighter the penalty of carrying external weapons will of course be higher as all the weapons are external. Still with only air-to-air missiles, I'd say their RCS should be much lower than clean MiG-29.
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Unread post30 Jan 2014, 12:54

hornetfinn wrote:
indochina wrote:The Real of RCS specs:

RCS of the missile would increased RCS of fighter.

For example AIM-9/120 or R-73/77 increased approximately 1m2 RCS per pylons and missiles.

=>>
F-15A RCS found in the range of 15-20-25m2, would grow RCS up to 150m2 with by the 10 A2A missile (or A2G missile, not including CFTs)
F-15C/E RCS 10-15m2 = 110m2 (hardpoint carry 11 A2A missile, not including CFTs)
J-11A/Su-27SK RCS 10-15m2 = 100m2 ( carry 10 A2A missile)
MiG-29 RCS 5m2 = 30m2 (6 A2A)
MiG-21/F-16A/Mirage 2000 RCS 3m2 = 12-18-27m2 (4-6-9 A2A)
MiG-29K/J-11B RCS 3m2 = 39m2 (13 A2A) / 30m2 (10 A2A)
F/A-18A/B/C/D RCS 3m2 = 27m2 (9 A2A)
Su-30MKK/MKI/MK2 RCS 4m2 = 48m2 (12 A2A)
Su-35S RCS 2-2.5m2 = 28m2 (14 A2A)
Rafale RCS 1.4m2 = 18-19.6m2 (14 A2A. Because 14 for Air Force versions (Rafale B/C), 13 for Navy version (Rafale M)
F-16C RCS 1.2m2 = 13.2m2 (11 A2A)
F/A-18E/F 1m2 = 11m2 (11 A2A)
EF-2000 RCS 0.5m2 = 6.5m2 (13 A2A)


To rectify this. The Russians use RAM for R-27 missiles while Americans use enclosed weapons pods for F/A-18E/F

http://www.fighter-planes.com/stealth2.htm
http://www.flightglobal.com/blogs/the-d ... od-mockup/

RAM for R-27 or other missile A2A of Russia, it will increase the weight but not too big, maintaining maneuverability of the aircraft. While the EWP for F/A-18 , it will increase the weight and do not guarantee reduced RCS


What is your source for these claims? I find it very strange that same amount of similar missiles would increase the RCS of F-15 or Su-27 to over 100 m2 and the RCS of Su-35, Rafale or F-16 to only 10-20 m2.

To me, it seems extremely unlikely that an air-to-air missile would have 1 m2 RCS except directly from side where it can be quite a lot larger than that. Even 1 degree off and it's likely to be much lower. Pylons are much the same, they likely have very low RCS, especially if designed with that in mind. Their largest RCS would be directly from side, but much can be done with good RAM treatment (with 15-20 dB lower RCS than without RAM).

There has been pretty good missile RCS experiments done and published, for example: http://www.jatm.com.br/ojs/index.php/jatm/article/viewFile/118/118

This shows Brazilian MAA-1 Piranha missile RCS calculations and experiment results. MAA-1 Piranha is somewhat like AIM-9L/M missile in shape and size. This shows that MAA-1 missile RCS is about 0.01 to 0.1 m2 except directly from behind where it's about 1 m2 and directly from side where it rises to about 50 m2. The result directly from sides is probably because the fins and wings act like corner reflectors. Missiles like AIM-9X, ASRAAM and AMRAAM (especially C- and D-models) have fins and wings that should work much better as they won't act like corner reflectors (due to their positioning, alignment and shape) and the RCS should be less than 1 m2 even from sides. Similarly they should have significantly lower frontal RCS due to much better (for low RCS) nose shape. These missiles also likely have been designed low RCS much more in mind than MAA-1 Piranha. I bet the RCS of F-35 with couple of external AIM-9X, ASRAAM or AMRAAM will be lower than 0.1 m2 frontally and less than 0.5 m2 directly from sides. For Rafale or Eurofighter the penalty of carrying external weapons will of course be higher as all the weapons are external. Still with only air-to-air missiles, I'd say their RCS should be much lower than clean MiG-29.


Thank for help :) I was wrong, I have used multiplication instead of calculus plus
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