F-22 and F-35 RCS revealed by USAF

Unread postPosted: 28 Nov 2005, 13:53
by boff180
Yes I am not BS'ing... I'll copy/paste the article below but to cut a long story short....

F-22 = metal marble
F-35 = metal golf ball (slightly less than B-2).

Nov 2005: The U.S. Air Force, in it’s effort to get money to build more F-22s, has revealed just how “stealthy” the F-22 is. It’s RCS (Radar Cross Section) is the equivalent, for a radar, to a metal marble. The less stealthy (and much cheaper) F-35, is equal to a metal golf ball. The F-35 stealthiness is a bit better than the B-2 bomber, which, in turn, was twice as good as that on the even older F-117. Much older aircraft, like the B-52, have a huge RCS, which makes them very easy to spot on radar. But with a smaller RCS, it's more likely that the aircraft won't be detected at all.

The air force revealed this information, which is usually kept secret, because it wants to make the case that it makes more sense to cut production of the F-35 (which cost $30-50 million each), so that more F-22s (that cost over $100 million each) can be bought. Most of the air force generals are former fighter pilots, and the F-22 is a much hotter fighter than the F-35 (which is basically a fighter-bomber, with emphasis on the latter function.) This is causing an international uproar, because of the many foreign countries that are buying the F-35. Some of these countries have contributed money for the development of the F-35. The F-22 will not be exported, because it uses so much top secret technology.


It also seems there is truth in the news reports the F-35A is for the chop.

Andy

RE: F-22 and F-35 RCS revealed by USAF.

Unread postPosted: 28 Nov 2005, 14:32
by toan
There are different size of Marbles.................

http://glassmarbles.com/size.htm

The range of the diameter for glassy marbles is from 12mm to 42mm, and according to the formula, the range of cross resection area for glassy marbles could be from 0.0001m2 to 0.0014m2..........

As for the marbles with the most common size (14.4mm and 16mm in diameter), their cross resection area shall be 0.00016m2 and 0.0002m2.....

Unread postPosted: 28 Nov 2005, 15:05
by elp
If JSF is a golf ball..... it is an "X -OUT". :lol:

Unread postPosted: 28 Nov 2005, 15:21
by toan
The standard golf ball today is 1.68 inch (4.2672 cm) in diameter.

According to formula, its cross resection area shall be around 0.00143m2, which is about 7~9 times bigger than the minimal frontal RCS of F/A-22, but 1/35~1/70 of the frontal RCS of the western NG LO-fighters such as EF-2000, Rafale, F/A-18E/F, and so on.

Unread postPosted: 28 Nov 2005, 15:29
by LordOfBunnies
These are also figures they're releasing to the public, I'm pretty sure they still have the actual value locked in a vault somewhere. The real values are probably also much smaller than what's available to the public. Best to not show your cards and all that.

Unread postPosted: 28 Nov 2005, 16:22
by Capt-soap
At what range would a block 50 f-16 radar,pick up a marble?

Unread postPosted: 28 Nov 2005, 16:35
by The_Mastiff
Toan, I knew I'd read somewhere the F22 had a lower RCS than the F117.(Per last conversation). I still haven't found the book it's in though.:'). Too many books, too little time ( typical old guy excuse).

While were on the subject if you redo your charts please try to include the Captor vs. Steel Marble. Thanks, JL Raleigh NC

Unread postPosted: 28 Nov 2005, 16:56
by toan
A UK test pilot declared that the maximum Air-to-air "tracking range" of CAPTOR radar is "significantly longer" than the 100 miles / 161km. (Source: AFM magazine 05/2004)

The same test pilot declared that with the help of Meteor AAM, the EF-2000 could attack the multiple aero-targets (up to 8 targets) as far as 200km away at the same time theoretically. (Source: RAF magazine 06/2004)

During the test, the CAPTOR radar showed the capability of tracking up to 20 air targets (F-4 and Mig-29) simultaneously 160~185 km away and then automatically identifying and prioritising them. (Source: EADS)

The RCS of the Mig-29 is about 5m2 class, so these informations may hint that CAPTOR radar now can "track" (not just detect) RCS = 5m2 class target 160~185 km away. According to the basic formula for the relationship between Target's RCS and Radar's effective detective / tracking range:

The maximally effective detective / tracking range of CAPTOR to F/A-22 (Minimal frontal RCS = 0.0001~0.0002m2 class) in head-to-head engagement should be 16~24 km / 11~15 km now theoretically.

According to the PDF at:
http://www.iee.org/oncomms/pn/radar/Roulston.pdf

I think that the figure in page 15 showed that the CAPTOR with AESA-upgrade's detective / tracking range is about 75% longer than the CAPTOR radar now.

So after 2012~2015, the maximally effective detective / tracking range of CAPTOR-AESA to F/A-22 (Frontal RCS = 0.0001~0.0002 m2 class) should be 28~42 km / 19~26 km theoretically.

Unread postPosted: 28 Nov 2005, 18:22
by The_Mastiff
Thank you Toan. :) JL Raleigh NC

Unread postPosted: 28 Nov 2005, 18:25
by Safetystick
So providing we get past the AMRAAM barrage (hope DASS works) we should be able to lock up with an ASRAAM.

Well, that's comforting! :P

Glad the only time this is likelly to happen is on exercise (I think the RAF can live with bruised pride!). Still, providing both aircraft can deal with the SU-30's and J-10's of the world I guess we should be happy!

Unread postPosted: 29 Nov 2005, 01:22
by toan
If RAF really wants to get more chance in BVR fighting with F/A-22, I think it should consider the development of something like Meteor BVRAAM with AESA + IIR dual seekers. With the help AWACS, datalink, and Pirate, it may have a more optimal effective range in engaging F/A-22 than Captor + Meteor or AIM-120...........

However, since USAF and RAF are as good friends as Harry Potter and Ron, it seems that this kind of development is meaningless for RAF up to now.........

Unread postPosted: 29 Nov 2005, 01:48
by TenguNoHi
However, since USAF and RAF are as good friends as Harry Potter and Ron, it seems that this kind of development is meaningless for RAF up to now.........


WTF is Ron?

-Aaron

Unread postPosted: 29 Nov 2005, 02:40
by Velvet
Skinny guy with a pet Rat.

Unread postPosted: 29 Nov 2005, 03:11
by Shonuff
isnt the US always improving upon its stealth technology?

Unread postPosted: 29 Nov 2005, 05:33
by toan
Shonuff wrote:isnt the US always improving upon its stealth technology?


Yes, so even the F/A-22 is not the highest achievement of stealthy techonology for USA now..........

According to a report from Popular Science in 2003, the scientists and engineers of USA have started to persue the new standard of stealth: RCS = -70dB, or 0.0000001 m2 class.............

As for Europeans, according to a recent report from EADS this year, it hopes to achieve -30db / 0.001m2-class RCS in its new UAV/UCAV that won't enter service before 2025, and its ultimate goal for the stealth of future UAV/UCAV that is settled now is -40dB / 0.0001m2, which should mean that it will take the countries in Western Europe another 20~25 years at least to achieve roughly the same class of stealthy capability that USAF has achieved since the end of 1990s...........

Unread postPosted: 29 Nov 2005, 07:26
by LordOfBunnies
Toan, do you know anything about the test aircraft Bird of Prey? I think it was a Boeing plane or some such. It was black for quite a while but was revealed recently. I saw somewhere (non reliable source) that it has a disturbingly small RCS.

Image

Unread postPosted: 29 Nov 2005, 08:05
by toan
This test plane was also introduced by the special report of Popular Science in 2003. It is said that a new and extendible covered skin had been used to this plane that made no gap on the surface of the whole plane, and with the help of the design of air-intake on back and removement of vertical tail, its frontal RCS is extremely small: 0.000026 m2, or about the 1/6 to 1/8 frontal RCS of F/A-22..........

Unread postPosted: 29 Nov 2005, 10:45
by boff180
Toan, didn't "replica" achieve the same RCS properties as the F-22; we did produce it to proove to Lockheed Martin that we were capable of producing stealth aircraft (ie. F-35 development)... but also publically showed our own stealth capabilities? Then again it was only declassified last year.

This is the only image that was released, this was taken in 1994!!! They claim it never flew but we don't believe them with good reason ;)
Image

Europe in a variety of different projects has been researching stealth for aslong as America; they just haven't funded operational aircraft... a good example is the "Lampyridae" a German/Dutch aircraft in the 1980's which looks very similar to the F-117.

Although there is one aircraft I can't understand us Euro's devloping.... Mako; who the hell wants a stealth Jet Trainer?? That would make a knightmare for positive air control especially with students at the controls!

Andy

Unread postPosted: 29 Nov 2005, 13:18
by Safetystick
Mako was... yeah, a little crazy.

Stealth was a tricky subject in EU. To get US level of funding we would need to work together and I don't think any of us trust each other enough to do that! There also seemed to be very little urgency in developing true stealth capabilities (kinda like trying to get the EU to develop stategic airlift capabilities). The closest we get is the RAF wanting F-117 (and would have likelly happened if the production line hadn't been closed).

Certainly us and the Germans had stuff that would have worked until funding got pulled, at least ours got incorporated into JSF. the Germans haven't had any return on their investment!

Given JSF (and bar it falling out of favour) I think European stealth effort will be directed into UCAV platforms, there are already a few projects gathering steam.

Unread postPosted: 29 Nov 2005, 15:50
by djcross
BoP was McDonnell Douglas' company-funded attempt to gain credibility in the VLO airplane world. They had participated in many contract competitions, but kept getting beat by Northrop, Lockheed and Rockwell. The VLO techniques and materials used in BoP were very ordinary. The interesting thing about BoP was the complex, highly integrated composite fueslage and wing carry through structure - one of the first in the industry. I saw it fly in December 1999 at Edwards, chased by 2 F-16s. Pretty cool. It was easy to tell what it was, but I did not know who built it at the time.

The "airplane" in boff180's picture is an RCS pole model used to gather empirical data to verify analytical RCS predictions. Pole models are typically built using a steel frame and fiberglass body in the desired shape and covered with RAM and RAS. A cylindrical rotation/tilt mechamism is built into the dorsal/ventral fuselage at the CG. This allows the model to spin and tilt on the inclined pole while RF measurements are being taken. The radar transmitter/receiver would be located off the left edge of the picture several hundred meters. The building over the model is likely on rails and would move aside to allow the R/T a clear shot at the pole model.

Unread postPosted: 29 Nov 2005, 15:57
by boff180
the photo was taken in BAE Systems Warton's state of the art radar hanger... (hence the pole model) but they claim the project named Replica never flew a "prototype" however strange aircraft pertaining to its shape were seen over the UK mid-late 1990's... the conspiracy theorists nicknamed the project then... HALO.

Unread postPosted: 29 Nov 2005, 16:49
by TenguNoHi
Replica is a very sharp looking a/c. Something like the proposed F-117 Navy and an F-35 or F-22. Pretty neat. Any other info available on it?

-Aaron

Unread postPosted: 29 Nov 2005, 17:08
by snypa777
Funny you should say that Aaron, was thinking the same thing.. The Replica has a Raptor looking front end and Nighthawk wings! It was never designed to be a completely stealthy aircraft but a look at what an affordable stealth plane could look like. That project has disappeared again into the blackness! Apparently it`s stealth and radar reflexivity targets were all met.Some of the ideas might find their way into JSF or may already have.

Anyone heard of the Su T-60 S stealth bomber? Would love to see a picture.

Unread postPosted: 29 Nov 2005, 17:46
by TenguNoHi

Unread postPosted: 29 Nov 2005, 18:12
by boff180
TenguNoHi wrote:Replica is a very sharp looking a/c. Something like the proposed F-117 Navy and an F-35 or F-22. Pretty neat. Any other info available on it?

-Aaron


All we know is the model was the product of a study into an indigenous Stealth aircraft which was revealed to exist in 2003.

All that was released was that it was the most extensive RCS study performed by the UK and that all its targets were met (unofficially attributed as: rcs of the f-22) and the project "completed" in 1999. Thats all that was said in a press release which accompanied the image. Thats all thats ever been heard of it.

Further to that, this year the MoD and BAe admitted they are developing a indigenous stealth UCAV under the project name: Nightjar. We have no idea what progress has been made on this but you can bet it has the lessons learned from Replica in it ;)

Andy

Unread postPosted: 29 Nov 2005, 20:02
by snypa777
Andy, on Nightjar, BAE are taking the technology from the project to the joint UCAV program being run between the UK/US. I would have thought we would go with the French n.E.U.R.O.n UCAV program. I don`t know the UK stance on that one.
Thanks for the link Aaron!

Unread postPosted: 30 Nov 2005, 03:26
by Obi_Offiah
toan wrote:A UK test pilot declared that the maximum Air-to-air "tracking range" of CAPTOR radar is "significantly longer" than the 100 miles / 161km. (Source: AFM magazine 05/2004)

The same test pilot declared that with the help of Meteor AAM, the EF-2000 could attack the multiple aero-targets (up to 8 targets) as far as 200km away at the same time theoretically. (Source: RAF magazine 06/2004)

During the test, the CAPTOR radar showed the capability of tracking up to 20 air targets (F-4 and Mig-29) simultaneously 160~185 km away and then automatically identifying and prioritising them. (Source: EADS)

The RCS of the Mig-29 is about 5m2 class, so these informations may hint that CAPTOR radar now can "track" (not just detect) RCS = 5m2 class target 160~185 km away. According to the basic formula for the relationship between Target's RCS and Radar's effective detective / tracking range:

The maximally effective detective / tracking range of CAPTOR to F/A-22 (Minimal frontal RCS = 0.0001~0.0002m2 class) in head-to-head engagement should be 16~24 km / 11~15 km now theoretically.

According to the PDF at:
http://www.iee.org/oncomms/pn/radar/Roulston.pdf

I think that the figure in page 15 showed that the CAPTOR with AESA-upgrade's detective / tracking range is about 75% longer than the CAPTOR radar now.

So after 2012~2015, the maximally effective detective / tracking range of CAPTOR-AESA to F/A-22 (Frontal RCS = 0.0001~0.0002 m2 class) should be 28~42 km / 19~26 km theoretically.


Nice post Toan.

Apparently the Captor is an order of magnitude in advance of one of the most 'recent' US manually steered array radars, the APG-73 if this article is anything to go by: http://www.dcmilitary.com/navy/tester/10_43/features/37863-1.html .
However it could be that the pilot/tester was refering to a specific scenario?. I find the comments quite surprising otherwise.

Obi

Unread postPosted: 30 Nov 2005, 07:00
by south
Hey all.

Long time lurker, first time poster.

Anyway, the problem with this sort of information is:
1. It has been released publicly. Generally safe to assume performance is going to be better, especcially in programs as secretive as the F-22 and F-35.
2. RCS information is pretty useless without an aspect angle and a frequency that it applies to.

Im pretty sure that figures similar to this have been released in the past,

Unread postPosted: 30 Nov 2005, 10:29
by toan
1. The definition of "Maximally effective detection range" for a certain target is the distance that the radar has 50% chance to detect the target.

2. The maximally effective detection range, the maximally effective tracking range, and the maximally effective engaging or locking range are not the same thing for a radar. Usually, the maximally effective tracking range for the radar to a certain target is 60~70% of its maximally effective detection range to the target. In addition, the effective range of STT is also longer than TWS.

(According to an article from Mr. Billsweetman a few year ago, the detection range of Captor to a standard fighter-sized target is about 185 km. However, in the report of AFM magazine 05/2004, the RAF pilot declared that maximally air-to-air "tracking range" of CAPTOR radar to MIG-29 had been "significantly longer" than the 100 miles / 161km, which should mean that its maximally air-to-air "detection range" to MIG-29 would be "significantly longer" than the 140~165 miles / 230~270 km theoretically..............I'm not sure which statement is closer to the real performance of Captor, but the previous estimation I made for Captor v.s F/A-22 was based on the statement of AFM magazine 05/2004.............)


3. The maximally effective detection / tracking / locking range of a radar to a certain target is also effected significantly by many other factors, such as relative height, RCS, ECM/ECCM, maneuver and so on........

Unread postPosted: 30 Nov 2005, 10:49
by toan
south wrote:Hey all.

Long time lurker, first time poster.

Anyway, the problem with this sort of information is:
1. It has been released publicly. Generally safe to assume performance is going to be better, especcially in programs as secretive as the F-22 and F-35.
2. RCS information is pretty useless without an aspect angle and a frequency that it applies to.

Im pretty sure that figures similar to this have been released in the past,



The similar information was released by AW&ST in 1999~2000:

The frontal RCS of F-22 is about 0.001 m2, or roughly equal to the size of a ping-pung ball, while the frontal RCS of JSF will be similar to a golf ball.

However, it seems that the stealthy capability of F/A-22 has been improved since then, and the frontal RCS of F/A-22 today is described as a metal marble, or even a hourse fly............

According to the special report of Popular Science in 2003 that I mentioned above, the smallest RCS that USA had achieved in its stealthy fighter (F/A-22???) at that time was: 5.2 cm2 (0.00052 m2, just as the size of a bigger glassy marble...........)

I think the minimal frontal RCS of F/A-22 today should be within the range between 0.00015 m2 to 0.00052 m2................. :idea:

Unread postPosted: 30 Nov 2005, 11:07
by toan
Final estimation:

According to the information from AFM magazine 05/2004 and the PDF at:
http://www.iee.org/oncomms/pn/radar/Roulston.pdf

1. The maximally effective detective / tracking range of CAPTOR to F/A-22 (Minimal frontal RCS = 0.00015~0.00052m2 class) in head-to-head engagement should be 17~31 km / 12~19 km now theoretically.

2. After 2012~2015, the maximally effective detective / tracking range of CAPTOR-AESA to F/A-22 today (Frontal RCS = 0.00015~0.00052 m2 class) should be 30~54 km / 21~33 km theoretically.


According to the information from Mr. Billsweetman and the PDF at:
http://www.iee.org/oncomms/pn/radar/Roulston.pdf

1. The maximally effective detective / tracking range of CAPTOR to F/A-22 (Minimal frontal RCS = 0.00015~0.00052m2 class) in head-to-head engagement should be 13~19 km / 10~13 km now theoretically.

2. After 2012~2015, the maximally effective detective / tracking range of CAPTOR-AESA to F/A-22 today (Frontal RCS = 0.00015~0.00052 m2 class) should be 23~33 km / 17~23 km theoretically.

Unread postPosted: 30 Nov 2005, 14:50
by elp
toan wrote:Final estimation:

According to the information from AFM magazine 05/2004 and the PDF at:
http://www.iee.org/oncomms/pn/radar/Roulston.pdf

1. The maximally effective detective / tracking range of CAPTOR to F/A-22 (Minimal frontal RCS = 0.00015~0.00052m2 class) in head-to-head engagement should be 17~31 km 11-18mi. / 12~19 km now theoretically. 9.2/11.4 mi

2. After 2012~2015, the maximally effective detective / tracking range of CAPTOR-AESA to F/A-22 today (Frontal RCS = 0.00015~0.00052 m2 class) should be 30~54 km / 21~33 km 18-32.4 mitheoretically.


According to the information from Mr. Billsweetman and the PDF at:
http://www.iee.org/oncomms/pn/radar/Roulston.pdf

1. The maximally effective detective / tracking range of CAPTOR to F/A-22 (Minimal frontal RCS = 0.00015~0.00052m2 class) in head-to-head engagement should be 13~19 km 11.4-13mi/ 10~13 km 6-11.4minow theoretically.

2. After 2012~2015, the maximally effective detective / tracking range of CAPTOR-AESA to F/A-22 today (Frontal RCS = 0.00015~0.00052 m2 class) should be 23~33 km 13.2-19.8mi/ 17~23 km10.2-13.8mi theoretically.


Ok now I can read it. :) Good info thanks.

Unread postPosted: 30 Nov 2005, 22:05
by snypa777
Are you Americans EVER gonna get decimalised!!!! :lol: :lol: :lol: :lol:

Unread postPosted: 30 Nov 2005, 22:32
by mark
Nope

Unread postPosted: 30 Nov 2005, 22:58
by snypa777
Heh heh!!! Good on ya! I work with a very old guy with 40 years in engineering. Whenever we give him fabrication drawings, the first thing he does is convert ALL the decimal units into imperial ones! He hates "new numbers" as he calls them!

Unread postPosted: 01 Dec 2005, 06:40
by 2sBlind
This way it confuses the bad guys out there when we call out ranges in NM. It's all part of our grand national security strategy.

Unread postPosted: 06 Dec 2005, 07:58
by ximeno
well I can tell you from a mechanic point of view, it sucks thinking that a bolt or hyd line is British, Metric or SAE. (Try removing a flap control valve on a hawker corporate jet)

Now my question after looking in aviation weekly and in this one issue there was a article about the Alaska F-15 with a big AESA type radar, about as big as the radar on the E's and K's. Now with them along with some of the F-18 Block2 AESA's, is it possible that with such a stronger, more sensitive radar that the f-22 can be seen? and I know I heard all of this talk about just "how stealthy" the f-22 but I have not heard anything about it against the aesa radars from our current military? :idea:

My strong belief is that the f-22, took way to long to get to this stage of development and I think it is outdated by something similar to more's law.

F-23 would have been the better choice.

Unread postPosted: 06 Dec 2005, 16:07
by elp
Moore wasn't a fighter pilot. :lol:

Unread postPosted: 06 Dec 2005, 16:31
by Guysmiley
Or an aerospace engineer. Jet fighters don't shrink in half every 18 months... And the F-22/F-23 argument is a whole 'nother can of worms. Yes, it looks cooler, but wouldn't it also be out of date now by your logic? Is it a better aircraft? There's a whole thread devoted to that debate.

Unread postPosted: 06 Dec 2005, 22:37
by Roscoe
And his aurguements got pounded there (by me) so he's bringing it here.

Plus, I love how everyone is posting on this thread like they're experts in RCS. Strange, never met an RCS guy talk in square meters. The unit of choice is decibals (square meter) or dBsm!!!! :poke:

There, I feel better... 8)

Unread postPosted: 06 Dec 2005, 22:54
by habu2
Roscoe wrote:Strange, never met an RCS guy talk in square meters.


A real RCS guy won't talk - period.

Unread postPosted: 07 Dec 2005, 09:43
by toan
1. As I've mentioned a lot of times before, I'm not a professional military expert or doctor, but just a military fan with special interest in modern fighters. In Japanese, I should be named as an "OTAKU".....:)

2. Personally, I like to talk RCS in square meter because in this way, I think the difference of RCS among fighters can be revealed more directly and clearly.

Unread postPosted: 07 Dec 2005, 09:51
by toan
ximeno wrote:well I can tell you from a mechanic point of view, it sucks thinking that a bolt or hyd line is British, Metric or SAE. (Try removing a flap control valve on a hawker corporate jet)

Now my question after looking in aviation weekly and in this one issue there was a article about the Alaska F-15 with a big AESA type radar, about as big as the radar on the E's and K's. Now with them along with some of the F-18 Block2 AESA's, is it possible that with such a stronger, more sensitive radar that the f-22 can be seen? and I know I heard all of this talk about just "how stealthy" the f-22 but I have not heard anything about it against the aesa radars from our current military? :idea:

My strong belief is that the f-22, took way to long to get to this stage of development and I think it is outdated by something similar to more's law.


About the effective detection range of AN/APG-77 according to AW&ST:

AW&ST 2000/03/17, 120 mile (192 km) at "Stealthy mode".

AW&ST 2000/03/17, 140 to 145 mile (260 to 270 km) at "Non-stealthy mode".

AW&ST 2000/03/17, radar image with 30 cm-class resolution for the target 100 miles (160 km) away.

AW&ST 2000/03/17, TWS 100 targets at the same time.


According to the reports of Mr.Billsweetman a few years ago, F/A-22 can detect the target of 400~460 km away with the help of ALQ-94 EWs. And the effective detection range of AN/APG-77 is about 185~230 km, which has some sacrifice because of energy / emission controlling for stealthy issue.

Some other reports said that AN/APG-77 has two kinds of detection modes. In the active mode, its effective detection range is about 230 km; while in the passive mode (The radar is as a receiver for enemy fighter's EM emission), its maximal effective range is about 400~460 km, but the datas which are gotten by this mode may not be precise enough to shoot BVRAAMs.

Unread postPosted: 07 Dec 2005, 13:04
by Shonuff
I've read in the book Lockheed Stealth that basically if the enemy starts blasting his radar all over the sky, the Raptor's passive sensors would be able to provide enough data for an AMRAAM shot.

Unread postPosted: 07 Dec 2005, 18:05
by Gums
Salute!

For all you folks wondering about a practical way to judge the RCS numbers.....

Read Ben Rich's book about the Skunk Works.

He talks about testing the RCS for the F-117 at Sandia. AND I PARAPHRASE the war story....

So they perch the F-117 or Have Blue or Senior Trend or other code name model on the wooden pole, or whatever. The Sandia engineer says something is wrong, as they can't get a "baseline" RCS or whatever. Just then a bird lands on the model and the equipment gets a reading. He tells the Lockheed folks, "O.K., our equipment is working now". And this was over 20 years ago.

be afraid, be very afraid. By the time you see a Raptor, you are about 23 milliseconds from having your brains splattered all over the combiner glass.

out,

Unread postPosted: 07 Dec 2005, 18:48
by Roscoe
Gums, you surprise me...surely you of all people know that it is really 69 milliseconds...

8)

Unread postPosted: 07 Dec 2005, 21:14
by elp
Is that like some sick preverted $ex joke Roscoe? That fighter pilots only use numbers in their briefings that are a multiple of 69 ? :lol:

Unread postPosted: 08 Dec 2005, 03:16
by Roscoe
Of course not... :roll:

Unread postPosted: 08 Dec 2005, 06:25
by 2sBlind
Yeah, what do you think we have our craniums in the gutter or something?

Unread postPosted: 08 Dec 2005, 08:19
by JR007
"So to speak"....

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 15 Jan 2006, 09:47
by avon1944
boff180 wrote:F-22 = metal marble
F-35 = metal golf ball (slightly less than B-2).

now, this metal marble and metal golf ball is detectible at what range? How far away is the signal being transmitted?

Adrian

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 15 Jan 2006, 15:55
by parrothead
avon1944 wrote:
boff180 wrote:F-22 = metal marble
F-35 = metal golf ball (slightly less than B-2).

now, this metal marble and metal golf ball is detectible at what range? How far away is the signal being transmitted?

Adrian


Adrian,

Detection range is completely dependant on the radar being used. Think of it this way - the better the radar's "eyesight" the longer the detection range. It's like an eye chart for people. Someone with superior eyesight (say 20/10 for example) can read the smaller characters at a greater distance than someone with poor eyesight. The characters on the chart are the same size.

The question here is how close does an enemy aircraft have to be to see something the size of a marble or a golf ball? That will vary depending on the radar in question that's trying to detect the object in question :wink: .

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 10 Nov 2014, 08:30
by mityan
Excuse me guys for bringing to top such an old topic, but there is one little thing that annoys me. I just cant get it out of my head.

I've heard that Raptor cockpit glass has a metallization layer.

I'm sure that overall reflections comrises of that ones from cockpit and from the rest of the airframe.

So how could the reflections from metallized cockpit glass (such a big metal plate - 45х27 inches front view) be less than from a small marble (1/2 inch wide)? Especially in broad range of angles.

Does anyone have a guess?

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 10 Nov 2014, 12:03
by hornetfinn
It's because the cockpit glass is such a shape that it redirects the reflections away from the radar. The glass is shaped in such a way that it does have continuously changing curves in three dimensions, which does this effect (doubly curved surface). A sphere has the same radii all around and it does reflect some of the radar energy back to the radar. A max RCS of a sphere is the area of the sphere as if it was a circle and it depends on the radar frequency. The reflecting area of the cockpit glass is extremely small compared to the geometrical area as only very small amount of the radar energy hitting it will go back towards the radar. The amount of overall reflected energy is not reduced much by the cockpit glass but reflecting it away from the radar does effectively the same thing.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 10 Nov 2014, 15:12
by sprstdlyscottsmn
That is the same reason why the "bumps" on the bottom of the F-35 that result from the skin being "shrink wrapped" around the munitions does not impact RCS. The location of said bumps also looks to me to be effective area ruling, but that is another discussion for another time.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 10 Nov 2014, 18:53
by smsgtmac
Wow. Not only was this a dead thread, but its since been acknowledged that the marble-golfball [phone spellchecker? hah!] comparison was wrong :D
Shape is an important element, but there's other considerations.
It helps to first think of the canopy as a "transparency" composed of multiple layers. Then recognize that whether a part of the plane you are dealing with will benefit the total system LO by being a conductor or insulator. From a physics POV there is no 'teflection' per se, but conversion to heat or re-radiation. The direction of the re-radiation is controlled in the design. GKNs website has a little "transparency" slide show illustrating how the canopy handles EM energy of a different sort. Handling energy from distant RF sources is trivial in comparison.
This is a particularly important design criteria for the F-35, because of the pyros installed in the transparency stack up. Sorry for any typos, but this was sent via a tiny phone screen and keyboard (fixed from the PC the same evening).

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 11 Nov 2014, 09:24
by mityan
hornetfinn wrote:It's because the cockpit glass is such a shape that it redirects the reflections away from the radar.
... The reflecting area of the cockpit glass is extremely small compared to the geometrical area as only very small amount of the radar energy hitting it will go back towards the radar.

I think it's not quite true because we are not in the region where the laws of optic propagation act.

In general, the the waves of any length (not only optic band) undergo the Huygens–Fresnel principle
https://en.wikipedia.org/wiki/Huygens%E2%80%93Fresnel_principle

According to it, every point which a luminous disturbance reaches becomes a source of a spherical wave; the sum of these secondary waves determines the form of the wave at any subsequent time.

This means that we may consider the canopy metal layer as a great antenna, which reradiates incident power.
It has its main lobe and side lobes just like any anttenna.

The mainlobe width is dependent on relatioship between antenna size (aperture) and wavelength.
The mirror in optic band, for example 1 meter long, will give the ratio near 2000000 times (optic waves are about 0.5 micrometer), and the beam is extremely narrow. And the sidelobes far from the main are extremely negligible (due to sin(x)/x function)

But what about X-band? For 1 m aperture and 0.03 m wave the ratio is only 33.
Then we get a picture like this:
angles.png

And what is the exact value of reflection? Look at this picture.
canopy.png

For tilted flat plane here is the RCS formula:
formula.png

It is taken from here:
http://books.google.by/books?id=XDs04HdQ4-gC&pg=PA183&lpg=PA183&dq=tilted+flat+plate+RCS&source=bl&ots=dol7wl54FC&sig=27W3hnnBtGpPkvwbuF5zzoA2oek&hl=ru&sa=X&ei=obZhVKDtG4HkOKL0geAC&ved=0CCcQ6AEwAg#v=onepage&q=tilted%20flat%20plate%20RCS&f=false
Why flat? We just cut a plane from a frontal part of canopy - 1 m long and 0.1 m wide - such a strip I think can be well approximated by flat plane.
Then we may remove all the rest of the canopy and all the rest of the airframe (though they also have a non-zero reflections)
and put the values in the formula (it seems the incidence angle is near 60 deg. to normal, A = the square of the strip)
So, we get the value of 0.00058 which is 5.8 times greater than reported overall RCS.
I want to remind that we nullified all other reflections from the airframe (!) and took just a narrow strip from canopy.

Everybody can calculate the square of circle, and that was done in 2005.
But also everyone can put the values in formula given above.
What you think guys?

My guess is that we've been reported a true minimal RCS value
value.png

which is fair for very narrow angle range. And a true average value is a definitely classified information and it should be much greater evidently.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 11 Nov 2014, 09:38
by mityan
smsgtmac wrote:From a physics POV there is no 'teflection' per se, but conversion to heat or re-radiation. The direction of the re-radiation is controlled in the design.

Reflection and reradiation are the same.
What about heat?
For consuming the electromagnetic wave and revert it to heating the matching is required. The impedance of the canopy's metal plate should be equal to impedance of a free space - 377 Ohm in broad range of frequencies.
As for me, I think that's a bullshit, but maybe this is due to a lack of education.
Consider the matching is implemented. For very good high frequency design the voltage standing wave ratio (VSWR) of near 1.5 is an adequate value. It means that only 20% of energy is reflected back to space.
So divide the estimated value above by 5 and you get the rcs still greater than reported.
There is no magic.

And what I think also.
Nobody could think of russians as stupid dumbass.
And if the CEO of OAK (united aviation corporation of russia) Pogosyan tells Putin that PAK-FA RCS is about 0.3 sq.m. and this is close to Raptor, I think he's got his reasons. There are too many candidates for his chair to fell free in lying.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 11 Nov 2014, 14:44
by smsgtmac
mityan wrote:
smsgtmac wrote:From a physics POV there is no 'teflection' per se, but conversion to heat or re-radiation. The direction of the re-radiation is controlled in the design.

Reflection and reradiation are the same....

Not exactly. The terms are used interchangeably as an irritatingly sloppy shorthand even by CEM guys, but pure reflection involves no absorption whereas re-radiation involves some increase in potential followed by the discharge/shedding or conversion of same.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 11 Nov 2014, 19:43
by KamenRiderBlade
smsgtmac wrote:
mityan wrote:
smsgtmac wrote:From a physics POV there is no 'teflection' per se, but conversion to heat or re-radiation. The direction of the re-radiation is controlled in the design.

Reflection and reradiation are the same....

Not exactly. The terms are used interchangeably as an irritatingly sloppy shorthand even by CEM guys, but pure reflection involves no absorption whereas re-radiation involves some increase in potential followed by the discharge/shedding or conversion of same.


The thing is, there will be some absorption, some reflection back to source, some radiating away from source when it comes to EM waves.

The question is how much of each will happen on the surface of the F-35 / F-22.

That's an answer that we'll probably never know until Stealth coatings become obsolete by some other tech and the US government reveals that fact.

In reality, there will probably be very little reflection back, a lot more radiating away via the wave hitting the surface at a non perpendicular angle, some absorption into heat depending on what type of RAM coating is used.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 11 Nov 2014, 19:46
by sergei
mityan wrote:
smsgtmac wrote:From a physics POV there is no 'teflection' per se, but conversion to heat or re-radiation. The direction of the re-radiation is controlled in the design.

Reflection and reradiation are the same.
What about heat?
For consuming the electromagnetic wave and revert it to heating the matching is required. The impedance of the canopy's metal plate should be equal to impedance of a free space - 377 Ohm in broad range of frequencies.
As for me, I think that's a bullshit, but maybe this is due to a lack of education.
Consider the matching is implemented. For very good high frequency design the voltage standing wave ratio (VSWR) of near 1.5 is an adequate value. It means that only 20% of energy is reflected back to space.
So divide the estimated value above by 5 and you get the rcs still greater than reported.
There is no magic.

And what I think also.
Nobody could think of russians as stupid dumbass.
And if the CEO of OAK (united aviation corporation of russia) Pogosyan tells Putin that PAK-FA RCS is about 0.3 sq.m. and this is close to Raptor, I think he's got his reasons. There are too many candidates for his chair to fell free in lying.


I think that talking about values ​​0.3 Pogosyan meant excluding anti-radar coating

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 12 Nov 2014, 07:37
by mityan
KamenRiderBlade wrote:In reality, there will probably be very little reflection back, a lot more radiating away via the wave hitting the surface at a non perpendicular angle, some absorption into heat depending on what type of RAM coating is used.

Some estimations just has been made. Maybe the exact values we'll be reported after decades, but it definitely should be much greater than -40 dBsm. Canopy has no RAM cause its destination is to provide an outside view for the pilot. I think it's hard to coinside with absorbing option.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 12 Nov 2014, 07:42
by mityan
sergei wrote:I think that talking about values ​​0.3 Pogosyan meant excluding anti-radar coating

And I guess not. It's XXI century and radar capabilities (also using an optic band) eliminate the VLO advantage, so it's not worth to tend to perfection - too expensive (and maybe suffers some physical limitations)...

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 13 Nov 2014, 03:54
by smsgtmac
mityan wrote:....It's XXI century and radar capabilities (also using an optic band) eliminate the VLO advantage, so it's not worth to tend to perfection ...


No.
You've made an assertion unsupported by fact. What is your case? By 'case', I mean a logical explanation, perhaps with supporting evidence from a credible source or sources that is specific enough to be proven either true or false. It is stated in the form of "This is true because_______________" (fill in the blank). A list of reasons is acceptable of course, but the reasoning and evidence must stand up to scrutiny and be free of logical fallacies.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 14 Nov 2014, 10:56
by mityan
smsgtmac wrote:"This is true because_______________" (fill in the blank).

Thanks for the compliment. :)
But I've told that it's my guess.
So I'll try to explain further.
PESA Irbis can detect target of -20 dBsm at the range up to 90 km. AESA N036 supposed to have equivalent capabilities (at least).
As for me, I doubt that Raptor has its overall -40 (my apologies, guys), but if it has, it can be detected at only 28 km range.
This is very good. But location equipment in optic band provides now greater ranges. And what about a2a missile firing range?
I dont know values but it seems to be greater also. And the firing event could rather be seen from the greater distance.
So what good is of X-band stealthy if you are seen due to fire? Thus I conclude that I should provide stealthy up to firing range and that is enough. Or maybe up to optic/IR band detection range. No more.
There is a very very big challenge to reduce observability for 10 dB e.g., and seems to be excess in the case described above.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 14 Nov 2014, 15:01
by hornetfinn
Sergei, optical/IR bands are good but they have also serious drawbacks for wide area surveillance. They offer no accurate range information and work only if there is no obscuration between the sensor and target. This means they can not tell target speed, altitude or heading accurately. Radar offers all that information and can detect targets in any weather. If optical sensors are to have long range, they have to have very narrow field of view. They are very useful tools, just like low frequency radars, but are miracle systems against stealth aircraft.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 14 Nov 2014, 15:36
by wrightwing
mityan wrote:
smsgtmac wrote:"This is true because_______________" (fill in the blank).

Thanks for the compliment. :)
But I've told that it's my guess.
So I'll try to explain further.
PESA Irbis can detect target of -20 dBsm at the range up to 90 km. AESA N036 supposed to have equivalent capabilities (at least).
As for me, I doubt that Raptor has its overall -40 (my apologies, guys), but if it has, it can be detected at only 28 km range.
This is very good. But location equipment in optic band provides now greater ranges. And what about a2a missile firing range?
I dont know values but it seems to be greater also. And the firing event could rather be seen from the greater distance.
So what good is of X-band stealthy if you are seen due to fire? Thus I conclude that I should provide stealthy up to firing range and that is enough. Or maybe up to optic/IR band detection range. No more.
There is a very very big challenge to reduce observability for 10 dB e.g., and seems to be excess in the case described above.


Detected at 28km, tracked at an even shorter range. Meanwhile, the F-22 detected the Flanker at 200+km, and T50 at 100+km, well before their optical systems would be of use.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 16 Nov 2014, 09:27
by mityan
wrightwing wrote:Detected at 28km, tracked at an even shorter range. Meanwhile, the F-22 detected the Flanker at 200+km, and T50 at 100+km, well before their optical systems would be of use.

And that is all? Is it so easy in your way?
double_facepalm.png

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 16 Nov 2014, 12:52
by disconnectedradical
From optimal angles such as head on, the F-22's RCS in the X-band is as low as 0.0001 sq m. The F-35 is 0.001 sq m, possibly lower. I think some disclosures by Sukhoi and reliable journalists suggest an optimal T-50 RCS of 0.05 to 0.01 sq m, which is still pretty low. However, T-50's side RCS will probably be much larger than the F-22 and F-35, due to the nearly 90 degree joint between the rear engine nacelles and fuselage.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 16 Nov 2014, 19:00
by arl8733
One other element which contributes to the F-22 metal marble being hard to detect is that it is traveling at 1.8M.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 17 Nov 2014, 08:02
by mityan
arl8733 wrote:One other element which contributes to the F-22 metal marble being hard to detect is that it is traveling at 1.8M.

No way. It's not an issue. The band of doppler frequencies being analyzed in any fighter or ground military radar receiver is wide enough to deal with this speed.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 17 Nov 2014, 08:13
by disconnectedradical
On another note, according to djcross, IF the T-50's RAM and manufacturing tolerances are good enough, its frontal RCS can approach the F-22 and F-35 at optimal angles/frequencies. Again, big emphasis on the if. As for all aspect, the shaping of the sides and rear means that all aspect VLO is probably not going to happen, though that's probably Sukhoi's intent. Stealth and reducing RCS is really about money, and how much money you're willing to throw at manufacturing tolerances, RAM, etc. And Russia just doesn't have as much money to throw at these details as the West. Still, the T-50 is quite good for a first attempt at stealth, and it's an excellent design when you consider the circumstances. And remember, the T-50 doesn't have to match the F-35 and F-22 to perform its mission. Not to mention that it has some unique attributes of its own, namely high maneuverability in all axis (though its usefulness is debatable), very high fuel capacity and range (3,500 km on internal fuel), and quite large weapons bay.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 17 Nov 2014, 09:18
by mityan
disconnectedradical wrote:From optimal angles such as head on, the F-22's RCS in the X-band is as low as 0.0001 sq m. The F-35 is 0.001 sq m, possibly lower. I think some disclosures by Sukhoi and reliable journalists suggest an optimal T-50 RCS of 0.05 to 0.01 sq m, which is still pretty low. However, T-50's side RCS will probably be much larger than the F-22 and F-35, due to the nearly 90 degree joint between the rear engine nacelles and fuselage.

F-22's RCS in the X-band is as low as 0.0001 sq m for a very narrow angle span - it's just a local mimimum, which is not relevant to an average RCS in wide angle span.
Please, look at the previous page of the topic - I just took a good american book on RCS an calculated the reflections from a small cut of metallized cockpit glass. Got a value greater than marble.
And please dont attribute a wonderful absorbing option to the glass - it's just a glass to see through, very strong, termal resistant, UV-filtering, etc. tough glass - but it's not radio absorbing.
So the calculation is rather close to reality I guess.

Another consideration.
Here are the US patents on RAM for example.
http://www.google.com/patents/US5310598
http://www.freepatentsonline.com/5164242.pdf
If you look attentively to the graphs showing loss vs. frequency,
you will understand that the absorbing capability of 25 dB is a very good result (especially in wide X + Ka band).
Materials with such losses can be implemented in fighter design.
What does this value mean?
25 dB = 300 times.
Thus if the conventional fighter is given near 3 sq.m. RCS, than for VLO design 3/300=0.01 sq.m. is an adequate figure.

There are some RAMs, that have a much greater losses, but they look like this:
http://tdkrfsolutions.com/images/uploads/data-sheets/TDK-IP130BL.pdf
And you realize that they cannot be implemented in fighter design.

So I truly believe that F-22 is still the most VLO fighter in the world, but its wide angle span RCS should be about 100 times greater than a metal marble.
I can believe that cockpit glass RCS could be slightly greater than 0.001, I can believe that overall design could be near 0.01, I can believe that the local minimum of RCS could be actually 0.0001 - but in a very narrow angle span, maybe 0.5 degree.

What you think?

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 17 Nov 2014, 09:20
by mityan
disconnectedradical wrote:Stealth and reducing RCS is really about money, and how much money you're willing to throw at manufacturing tolerances, RAM, etc. And Russia just doesn't have as much money to throw at these details as the West.

For a pity, money cannot fight physics.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 17 Nov 2014, 10:44
by disconnectedradical
mityan wrote:
disconnectedradical wrote:Stealth and reducing RCS is really about money, and how much money you're willing to throw at manufacturing tolerances, RAM, etc. And Russia just doesn't have as much money to throw at these details as the West.

For a pity, money cannot fight physics.

No, it's not fighting physics. Closer manufacturing tolerances will result in lower overall RCS since it reduces the effects of surface discontinuity. How close you can get the tolerances is pretty much dependant on how much money you want to throw at manufacturing.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 17 Nov 2014, 11:01
by mityan
disconnectedradical wrote:Closer manufacturing tolerances will result in lower overall RCS since it reduces the effects of surface discontinuity.

Closer manufacturing tolerances give a practical results closer to a simulated ones. But what about metallized canopy? In that case the tolerance, which is negligible to wavelength, gives a negligible advantage. Do you think the application case of the formula isn't quite correct?

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 18 Nov 2014, 15:00
by hornetfinn
mityan wrote:Why flat? We just cut a plane from a frontal part of canopy - 1 m long and 0.1 m wide - such a strip I think can be well approximated by flat plane.
Then we may remove all the rest of the canopy and all the rest of the airframe (though they also have a non-zero reflections)
and put the values in the formula (it seems the incidence angle is near 60 deg. to normal, A = the square of the strip)
So, we get the value of 0.00058 which is 5.8 times greater than reported overall RCS.


The result is heavily influenced by wavelength used in calculations and also on exact incident angle. Of course the canopy is also quite a bit more complicated object than your approximation and that can result in quite significant differences. Also it might be that the canopy does not have perfect reflectivity but rather attenuates the radar waves with some mechanism.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 18 Nov 2014, 16:46
by wrightwing
mityan wrote:
wrightwing wrote:Detected at 28km, tracked at an even shorter range. Meanwhile, the F-22 detected the Flanker at 200+km, and T50 at 100+km, well before their optical systems would be of use.

And that is all? Is it so easy in your way.


Which is where having significant RCS advantages, also provide enormous tactical advantages.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 18 Nov 2014, 16:55
by wrightwing
mityan wrote:
disconnectedradical wrote:Closer manufacturing tolerances will result in lower overall RCS since it reduces the effects of surface discontinuity.

Closer manufacturing tolerances give a practical results closer to a simulated ones. But what about metallized canopy? In that case the tolerance, which is negligible to wavelength, gives a negligible advantage. Do you think the application case of the formula isn't quite correct?

They didn't spend all the time, effort, and money on RCS reduction of the airframe, to haphazardly throw a canopy that negates these effects. The design is intentional, to prevent RF radiation from reflecting off the non-stealthy contents of the cockpit. Stealth isn't just about eliminating reflectivity, but controlling it, and using it in your favor.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 19 Nov 2014, 06:51
by mityan
hornetfinn wrote:The result is heavily influenced by wavelength used in calculations and also on exact incident angle. Of course the canopy is also quite a bit more complicated object than your approximation and that can result in quite significant differences. Also it might be that the canopy does not have perfect reflectivity but rather attenuates the radar waves with some mechanism.

1. Just vary wavelength in fighter radar band (X), vary angles and see "the heaviness" of this influence.
2. I took just a little cut from the canopy assuming all other reflection are zero. So the result figure is less than real. The formula in the book represents a kind of continuous function
https://en.wikipedia.org/wiki/Continuous_function
so a little variation cannot result in "quite significant" difference.
3. "it might be" together with "most likely" are your favourite sentences in any analysis. What mechanism?

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 19 Nov 2014, 07:09
by mityan
wrightwing wrote:Which is where having significant RCS advantages, also provide enormous tactical advantages.

Raptor average frontal RCS is close to 0.01 sq.m.
It can be tracked far enough by means of aerial or ground radar.
Why?
The answer is in the first post in this thread:
Nov 2005: The U.S. Air Force, in it’s effort to get money to build more F-22s, has revealed just how “stealthy” the F-22 is. It’s RCS (Radar Cross Section) is the equivalent, for a radar, to a metal marble.

TO GET MORE MONEY.

Very, very nice try! What a wonderful fairytales can we invent in order to get more money!
They revealed the local narrow angle minimum RCS and made everyone to believe it's actual value.
(Special thanks to Fulghum from AW journal - he wrote that -40 dBsm is ALL-ASPECT RCS).
f2221.jpg

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 19 Nov 2014, 07:15
by mityan
wrightwing wrote:They didn't spend all the time, effort, and money on RCS reduction of the airframe, to haphazardly throw a canopy that negates these effects. The design is intentional, to prevent RF radiation from reflecting off the non-stealthy contents of the cockpit.

Metallized canopy reduces RCS, because it has smoothed surface and it covers the cockpit interior, the elements of which might have significantfy higher RCS.
wrightwing wrote: Stealth isn't just about eliminating reflectivity, but controlling it, and using it in your favor.

How the glass or metal film controles reflectivity? You are free to hope so.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 19 Nov 2014, 07:42
by wrightwing
mityan wrote:
wrightwing wrote:They didn't spend all the time, effort, and money on RCS reduction of the airframe, to haphazardly throw a canopy that negates these effects. The design is intentional, to prevent RF radiation from reflecting off the non-stealthy contents of the cockpit.

Metallized canopy reduces RCS, because it has smoothed surface and it covers the cockpit interior, the elements of which might have significantfy higher RCS.
wrightwing wrote: Stealth isn't just about eliminating reflectivity, but controlling it, and using it in your favor.

How the glass or metal film controles reflectivity? You are free to hope so.

You might want to do some more reading on the subject, before you embarrass yourself any more. The metal oxide finish on the canopy glass not only prevents RF energy from reflecting off the surfaces inside the cockpit (which product large returns), but attenuates the RF energy, and ensures that it isn't reflected back to the source. This is the principle of the entire airframe- to direct reflections away from source emitters, and in controlled shapes. There's no hoping involved. Merely physics.

Your RCS rebuttal is equally laughable. You're attempting to draw empirical conclusions, based upon an analogy. Stick to youtube comments. That's a better forum for this level of discourse.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 19 Nov 2014, 09:48
by mityan
wrightwing wrote:This is the principle of the entire airframe- to direct reflections away from source emitters, and in controlled shapes. There's no hoping involved. Merely physics.

Yes. It is physics. Some energy (a very small amount) is reflected back according to formulas. And this gives the result that is greater than you want it to be.
You dont know physics, you dont know the principles - how metal plate or glass can absorb wave, but to insist on this - is your duty.
Not hope, but faith.
I've posted the formula, the link to a good american book on RCS.
I've posted US patents on RAM - with the absorbtion figures.
And what is your ground? What are you based on, what should I learn to know your point?

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 19 Nov 2014, 15:50
by archangel117
mityan wrote:
hornetfinn wrote:It's because the cockpit glass is such a shape that it redirects the reflections away from the radar.
... The reflecting area of the cockpit glass is extremely small compared to the geometrical area as only very small amount of the radar energy hitting it will go back towards the radar.

I think it's not quite true because we are not in the region where the laws of optic propagation act.

In general, the the waves of any length (not only optic band) undergo the Huygens–Fresnel principle
https://en.wikipedia.org/wiki/Huygens%E2%80%93Fresnel_principle

According to it, every point which a luminous disturbance reaches becomes a source of a spherical wave; the sum of these secondary waves determines the form of the wave at any subsequent time.

This means that we may consider the canopy metal layer as a great antenna, which reradiates incident power.
It has its main lobe and side lobes just like any anttenna.

The mainlobe width is dependent on relatioship between antenna size (aperture) and wavelength.
The mirror in optic band, for example 1 meter long, will give the ratio near 2000000 times (optic waves are about 0.5 micrometer), and the beam is extremely narrow. And the sidelobes far from the main are extremely negligible (due to sin(x)/x function)

But what about X-band? For 1 m aperture and 0.03 m wave the ratio is only 33.
Then we get a picture like this:
angles.png

And what is the exact value of reflection? Look at this picture.
canopy.png

For tilted flat plane here is the RCS formula:
formula.png

It is taken from here:
http://books.google.by/books?id=XDs04HdQ4-gC&pg=PA183&lpg=PA183&dq=tilted+flat+plate+RCS&source=bl&ots=dol7wl54FC&sig=27W3hnnBtGpPkvwbuF5zzoA2oek&hl=ru&sa=X&ei=obZhVKDtG4HkOKL0geAC&ved=0CCcQ6AEwAg#v=onepage&q=tilted%20flat%20plate%20RCS&f=false
Why flat? We just cut a plane from a frontal part of canopy - 1 m long and 0.1 m wide - such a strip I think can be well approximated by flat plane.
Then we may remove all the rest of the canopy and all the rest of the airframe (though they also have a non-zero reflections)
and put the values in the formula (it seems the incidence angle is near 60 deg. to normal, A = the square of the strip)
So, we get the value of 0.00058 which is 5.8 times greater than reported overall RCS.
I want to remind that we nullified all other reflections from the airframe (!) and took just a narrow strip from canopy.

Everybody can calculate the square of circle, and that was done in 2005.
But also everyone can put the values in formula given above.
What you think guys?

My guess is that we've been reported a true minimal RCS value
value.png

which is fair for very narrow angle range. And a true average value is a definitely classified information and it should be much greater evidently.

Let me get this straight, you are trying to cut a flat plane out of an object designed with continuous curvature? Seems to me it would be obvious that you would get a higher RCS from a flat plate than a continuous curve designed to "obsorb", attenuate and "reflect" RF energy away from the receiver. This isn't an F-117 it has very few flat surfaces, even it's saw-tooth edges are not completely flat. So I suggest you figure out how to fit the curvature of the canopy into the equation.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 19 Nov 2014, 16:10
by wrightwing
mityan wrote:
wrightwing wrote:This is the principle of the entire airframe- to direct reflections away from source emitters, and in controlled shapes. There's no hoping involved. Merely physics.

Yes. It is physics. Some energy (a very small amount) is reflected back according to formulas. And this gives the result that is greater than you want it to be.
You dont know physics, you dont know the principles - how metal plate or glass can absorb wave, but to insist on this - is your duty.
Not hope, but faith.
I've posted the formula, the link to a good american book on RCS.
I've posted US patents on RAM - with the absorbtion figures.
And what is your ground? What are you based on, what should I learn to know your point?


You should learn that shaping is the most important aspect of stealth, as it minimizes the amount of energy that is reflected back to the source. RAM works in conjunction with shaping, to further reduce reflectivity. The interior of a cockpit has a lot of highly reflective sources, so.....the goal of signature reduction, is to prevent RF energy from entering/reflecting off of these surfaces. The SHAPE and composition of the canopy minimizes any returns, to the source. You can't gain any useful information, regarding signature reduction, if you're trying to base it off of a chunk of material. For your sake, and for the rest of us, put your google skills to use, and read about signature reduction measures incorporated in canopies.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 20 Nov 2014, 00:28
by arl8733
Anybody here know how long the coatings on the transparency are lasting these days? Knew it was a problem in the early days.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 20 Nov 2014, 08:05
by mityan
archangel117 wrote:Let me get this straight, you are trying to cut a flat plane out of an object designed with continuous curvature? Seems to me it would be obvious that you would get ...

Sure!
And I do it with success, like all mathematicians in the world.
surface.png

You must be surprized that delta Si at the picture is a flat square.
I just cut this:
canopy_cut.png

This is flat enough for 3-cm wave dont you think?
Or do you think 1-mm inaccuracy (difference between flat and curve) may result in 10 or even 100 times in reflection?

Let me get this straight too. You are trying to apply optical propagation laws to X-band radiowave in spite of incomparable wavelength/object size ratio? Seems to me it would be obvious that you would get a much lower RCS just like radar signal is a laser beam and canopy is usual mirror.

The radiated energy, in fact, takes a pattern like a typical reflected wave structure. The width of the main forward scattered spike is proportional to the ratio of the wavelength to the dimension of the reradiating surface, as are the magnitudes of the secondary and tertiary spikes. The classical optical approximation applies when this ratio approaches zero. Thus, the backscatter - the energy radiated directly back to the transmitter increases as the wavelength goes up, or the frequency decreases.

It is taken from here:
http://www.globalsecurity.org/military/systems/aircraft/f-22-stealth.htm
ratio approaches zero - 0.0000005 m - length of optical wave - is almost 0 compared to that cut (see above)
But how about 0.03 m length of X-band wave?

There is NO alternative physics for reflection. Just Huygens–Fresnel principle I've mentioned previously.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 20 Nov 2014, 09:56
by archangel117
mityan wrote:
archangel117 wrote:Let me get this straight, you are trying to cut a flat plane out of an object designed with continuous curvature? Seems to me it would be obvious that you would get ...

Sure!
And I do it with success, like all mathematicians in the world.
surface.png

You must be surprized that delta Si at the picture is a flat square.
I just cut this:
canopy_cut.png

This is flat enough for 3-cm wave dont you think?
Or do you think 1-mm inaccuracy (difference between flat and curve) may result in 10 or even 100 times in reflection?

Let me get this straight too. You are trying to apply optical propagation laws to X-band radiowave in spite of incomparable wavelength/object size ratio? Seems to me it would be obvious that you would get a much lower RCS just like radar signal is a laser beam and canopy is usual mirror.

The radiated energy, in fact, takes a pattern like a typical reflected wave structure. The width of the main forward scattered spike is proportional to the ratio of the wavelength to the dimension of the reradiating surface, as are the magnitudes of the secondary and tertiary spikes. The classical optical approximation applies when this ratio approaches zero. Thus, the backscatter - the energy radiated directly back to the transmitter increases as the wavelength goes up, or the frequency decreases.

It is taken from here:
http://www.globalsecurity.org/military/systems/aircraft/f-22-stealth.htm
ratio approaches zero - 0.0000005 m - length of optical wave - is almost 0 compared to that cut (see above)
But how about 0.03 m length of X-band wave?

There is NO alternative physics for reflection. Just Huygens–Fresnel principle I've mentioned previously.

Mityan, respecfully, you seem to have a skewed view on how this works. In the world of stealth even the smallest features can radically change the RCS of an object, yes even a Milimeter, this is why the F-22 and F-35 have borderline ludicrous tolerances.
You seem on the right track with some of your math but still off the mark with the final numbers.
Here: http://www.academia.edu/5672531/Radar_C ... _UHF_Bands
We can see that the Frontal RCS of the F-22 as simulated in the X band is roughly -18 dBsm. This is without R.A.M or R.A.S and is admitted by them to be a imperfect model of the craft. Yet if we apply the values for the R.A.M depicted in figure 7 here: http://www.freepatentsonline.com/5164242.pdf it can easily be seen how the RCS in the X-band can be -40 dBsm In the frontal aspect.

This is the physics as done by a professional software setup by professional people and using data from a patent you found. It can be seen that your method of calculation needs some work as your values do not match the simulations.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 21 Nov 2014, 09:24
by mityan
archangel117 wrote:In the world of stealth even the smallest features can radically change the RCS of an object, yes even a Milimeter

Very doubtful statement. According to conventional physics 1 mm should not have a significant influence on 30-mm wave.
Where is that world of stealth - in alternative universe?
archangel117 wrote:Here: http://www.academia.edu/5672531/Radar_C ... _UHF_Bands
We can see that the Frontal RCS of the F-22 as simulated in the X band is roughly -18 dBsm.

First of all - not -18 but -9 dBsm:
rcs2.png

archangel117 wrote:This is without R.A.M or R.A.S and is admitted by them to be a imperfect model of the craft. Yet if we apply the values for the R.A.M depicted in figure 7 here: http://www.freepatentsonline.com/5164242.pdf it can easily be seen how the RCS in the X-band can be -40 dBsm In the frontal aspect.

I dont know the CST program, but ADS by Agilent and Microwave office by AWR are similar to it (designed for the same tasks). I simulated just a small phased array antenna (near 30 elements) and the process took a significant part of my 64 GB RAM (compare to 500 MB in the article) and lasted also several hours. And very doubtful that they have a 3D model of Raptor with 1-mm precision. But the improvement in model precision may lead to a better or a worse result with an equal probability.
Go ahead. Take this picture:
rcs.png

and this:
ram.png

You see that we can get a value near -13 dBsm (0.05 sq.m.) at 10 GHz.
And what I calculated earlier - a piece of canopy, it is not covered with RAM so the laue I got - 0.00058 - is still a part of overall RCS, even if the RAM attenuation will be applied to a model.

I want to say again. I DO NOT reject the value of -40 dBsm at all.
I believe that it is true, but with some more specification of its applicability. I've told about its narrow angle localization, and here is frequency dependence too.
So this is not a figure we can rely on upon estimating tracking range etc.

What about USAF officials - they wanted to compliment themselves.
And they wanted to get more money for further Raptor production.
Just businness, nothing wrong with it.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 21 Nov 2014, 14:28
by hornetfinn
mityan wrote:3. "it might be" together with "most likely" are your favourite sentences in any analysis. What mechanism?


Because without accurate specs, we don't know for certain and really accurately but we can make decent estimates with the knowledge we have.

I don't think the coating in F-22 or F-35 canopy is a fully reflective coating but more likely works as a layer that behaves like anti-radiation paint. Why does this coating need to be reflective at all? There are anti-radiation paints that can attenuate the reflections at least 15 dB.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 23 Nov 2014, 09:16
by mityan
hornetfinn wrote:I don't think the coating in F-22 or F-35 canopy is a fully reflective coating but more likely works as a layer that behaves like anti-radiation paint. Why does this coating need to be reflective at all? There are anti-radiation paints that can attenuate the reflections at least 15 dB.

Did you read anywhere about thin film transparent paint with such a high attenuation, or it is just a dream?

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 23 Nov 2014, 18:37
by smsgtmac
Mityan,
You appear to have some minimal understanding of mathematics for RCS estimation, but you have a woefully insufficient grasp of RF physics and LO/RCS reduction techniques. On top of his, you've gone from being amusing to irritatingly arrogant in your arrogance (Hybris). You've become tiresome.

I have some things to do today, and when I come back this evening I'm going to show you precisely where you are sadly lacking in the knowledge that you have so eagerly 'shared' here -- and I will do so without going beyond using the information you have posted and just two introductory textbooks on the fundamentals of LO/stealth.

'How' I will do this depends upon your answers to two questions:
1) How old are you?
2) Do you have access to Amazon.com?

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 24 Nov 2014, 06:26
by KamenRiderBlade
smsgtmac wrote:Mityan,
You appear to have some minimal understanding of mathematics for RCS estimation, but you have a woefully insufficient grasp of RF physics and LO/RCS reduction techniques. On top of his, you've gone from being amusing to irritatingly arrogant in your arrogance (Hybris). You've become tiresome.

I have some things to do today, and when I come back this evening I'm going to show you precisely where you are sadly lacking in the knowledge that you have so eagerly 'shared' here -- and I will do so without going beyond using the information you have posted and just two introductory textbooks on the fundamentals of LO/stealth.

'How' I will do this depends upon your answers to two questions:
1) How old are you?
2) Do you have access to Amazon.com?


(Hybris) = (Hubris)

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 24 Nov 2014, 06:51
by smsgtmac
KamenRiderBlade wrote:
smsgtmac wrote:Mityan,
You appear to have some minimal understanding of mathematics for RCS estimation, but you have a woefully insufficient grasp of RF physics and LO/RCS reduction techniques. On top of his, you've gone from being amusing to irritatingly arrogant in your arrogance (Hybris). You've become tiresome.

I have some things to do today, and when I come back this evening I'm going to show you precisely where you are sadly lacking in the knowledge that you have so eagerly 'shared' here -- and I will do so without going beyond using the information you have posted and just two introductory textbooks on the fundamentals of LO/stealth.

'How' I will do this depends upon your answers to two questions:
1) How old are you?
2) Do you have access to Amazon.com?


(Hybris) = (Hubris)


Heh. I've adopted the late, great, Professor J. Rufus Fears' convention of using the Greek phonetic spelling of 'Hybris'.
BTW: I was originally going to type "Arrogance in your Ignorance" but I typo'd it and then decided "Arrogance in your Arrogance" worked just as well. Thought for sure someone would've said something about that one :wink:

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 24 Nov 2014, 07:30
by smsgtmac
Well Mityan, you didn’t answer the questions, so my working assumption is you are a grownup with a credit card and an Amazon.com account.
First, your approach in applying a flat-plate model of the RF behaviors of a notional F-22 canopy is completely contrived and erroneous.
mityan wrote:...And what is the exact value of reflection? Look at this picture.
mityans-canopy-cartoon.jpg

For tilted flat plane here is the RCS formula:
mityans-source-formula.jpg

It is taken from here:
http://books.google.by/books?id=XDs04HdQ4-gC&pg=PA183&lpg=PA183&dq=tilted+flat+plate+RCS&source=bl&ots=dol7wl54FC&sig=27W3hnnBtGpPkvwbuF5zzoA2oek&hl=ru&sa=X&ei=obZhVKDtG4HkOKL0geAC&ved=0CCcQ6AEwAg#v=onepage&q=tilted%20flat%20plate%20RCS&f=false
Why flat? We just cut a plane from a frontal part of canopy - 1 m long and 0.1 m wide - such a strip I think can be well approximated by flat plane.
Then we may remove all the rest of the canopy and all the rest of the airframe (though they also have a non-zero reflections)
and put the values in the formula (it seems the incidence angle is near 60 deg. to normal, A = the square of the strip)
So, we get the value of 0.00058 which is 5.8 times greater than reported overall RCS.
I want to remind that we nullified all other reflections from the airframe (!) and took just a narrow strip from canopy.
...
My guess is that we've been reported a true minimal RCS value
...
which is fair for very narrow angle range. And a true average value is a definitely classified information and it should be much greater evidently.


No....Not Even Close.
The ‘flat plate’ equation you present is not relevant to a flat plate tilted at the angle indicated. If you had read the paragraph after that equation in your source, you would have read this:
Inappropriate-use-of-calibration-formula.jpg

Note the highlighted point of interest.
Now, if you had a more complete reference for estimating flat plate specular reflection at hand, say Radar Cross Section, Second Edition, by E.F. Knott (same author as your source), J.F. Shaeffer, and M.T. Tuley, you would know how to treat estimating the specular return of a tilted flat plate:
If the plate is oriented off the specular angle, but in such a way as to maintain a pair of edges perpendicular to the radar line of sight, the radar return is no longer proportional to the square of the area, but to the square of the edge length. (P. 7)

Your ".1m" edge would have a .1m^2 effective area. Guess what that does to your calculations.
This is just the tip of the iceberg you hit. At aspect angles greater than ~40 degrees, the relevance of the theory of physical optics “gives way” (Knott et al, P. 232) to edge diffraction (as indicated in the quote above) and surface travelling wave echo. The dominance of each of these effects depends upon polarity. These mechanisms, in total, are the ‘reradiation’ that I noted earlier.

So even your understanding of the flat plate specular behavior is wrong. But that’s OK, because the flat plate model doesn't even apply to a curved surface such as the canopy under consideration.

Curved surfaces require treating specular diffraction of RF energy as a return from striking a "specular point" (Knott et al, P. 549). I have no desire to spend my time explaining what this means, even if we just covered what we could find in the public domain. ‘Knott et al’ is 600 pages long, not counting index, and even they don’t cover everything.
But even if we could simply solve the RCS of an LO aircraft canopy assembly, it still wouldn’t give you an answer that you could generalize into an overall aircraft RCS. Why? You can't presume the canopy's standalone RCS value is relevant.

David Lynch, in his Introduction to RF Stealth (hyperlink fixed), provides an excellent overview of stealth as being the total of operational techniques and aircraft design, and an advanced high school student could follow most of it Aside from one unfortunate anecdote that is an urban myth, I find it excellent in presenting the whole stealth perspective. He presents the material in the framework of the ‘Great Thoughts’ of LO/Stealth (PP. 5-8):

1. Active emissions control must be coupled with platform cross-section reduction.
2. Planform alignment: concentrating all the reflections (hate that word) in a few directions can reduce the RCS in all other directions.
3. Facets and shaping: selecting shapes that present very low sidelobes towards threats
4. Edge treatment by convolution; i.e. using a mathematical function such as a Gaussian convolved on the junction of two surfaces to create a “blend” a very low RCS sidelobes
5. Impedance control: ensuring there are no discontinuities in the platform surface impedance, edge treatment by impedance matching of the platform skin to free space
6. Exploitation of the environment.

Of particular interest, because they relate to how your argumentation and knowledge base fails, are numbers 4 and 5.
“4?” You cannot treat the RCS of the canopy as an independent RCS number if it is integrated into the overall design such that the canopy is properly ‘blended’ into the rest of the aircraft.
“5?” A good LO aircraft has excellent impedance matching between its constituent components and to the airstream.

Now, go read up on this stuff.
Come back when you know as much as you thought you did.

(Unless you were just trolling. Then just go away.)

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 24 Nov 2014, 09:17
by geforcerfx
smsgtmac.... :shock:


:notworthy: :notworthy: :notworthy: :notworthy: :notworthy: :notworthy: :notworthy: :notworthy: :notworthy:

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 24 Nov 2014, 09:39
by KamenRiderBlade
If you tried to 3D model the radar reflections off of the F-22 / F-35 using ray tracing from every possible point in the sphere with a .1 degree spacing between each point, I'm pretty sure the RCS at each point should be pretty low given the contours of the aircraft is designed to not be seen except at very specific points.

From straight below / above, all aircraft should have the highest RCS.

But to align your radar with a moving aircraft in that manner is a next to impossible task, so the risk is negligible.

To try to calculate the RCS from straight ahead, I'm sure the scientist / engineers at Lockheed Martin planned every curve to lower the overall RCS from every angle that matters.

Lockheed Martin is one of 2 companies with real world experience in Stealth. The other company being Northrop Grumman.

If you think you can outdo the world's leading defense contractors with cursory knowledge, you must be mentally challenged.

Even with my level of knowledge of 3D vector math, geometry, and ray reflections; I can tell that you are not going to get much if any RF sources reflected back to the source unless you're directly under or above, and realistically, that's not going to happen.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 24 Nov 2014, 13:21
by hornetfinn
mityan wrote:
hornetfinn wrote:I don't think the coating in F-22 or F-35 canopy is a fully reflective coating but more likely works as a layer that behaves like anti-radiation paint. Why does this coating need to be reflective at all? There are anti-radiation paints that can attenuate the reflections at least 15 dB.

Did you read anywhere about thin film transparent paint with such a high attenuation, or it is just a dream?


Well, how about a patent about such transparent radar absorbing coating from Westinghouse Electric Corporation which was filed in 1992: http://www.google.com/patents/US5358787

Up to almost 50 dB reduction in X-band radar reflection or another design with 15 dB reduction in very wide bandwidth...

Interesting that the date of that patent would fit rather nicely with F-22 development...

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 25 Nov 2014, 10:06
by mityan
smsgtmac wrote:No....Not Even Close.
The ‘flat plate’ equation you present is not relevant to a flat plate tilted at the angle indicated. If you had read the paragraph after that equation in your source, you would have read this:
formula_again.png

Note the highlighted point of interest.

What does it mean? Let me explain.
If we have a laboratory, a set of devices to generate and measure a signal of interest, and we are going to perform some precise measurements, we should at first calibrate our devices. It means the measurement of exactly known pattern.
Let's take a closer look to the formula - biuld a dependency on freq (6-15 GHz) and in wide angle span:
formula_dependence.png

So, indeed, we can calibrate ony in very narrow angle span near normal line.
But stop now!
Why we are talking about calibration at all? Who cares of it?
Does it mean that the formula is wrong or has a limited usage (i.e. rcs of plane undergoes different laws)?
NO.
So what was that? What kind of logical fallacy -
Composition fallacy - http://www.nizkor.org/features/fallacies/composition.html
or Red Herring ? http://www.nizkor.org/features/fallacies/red-herring.html

Go further.
formula_dependence2.png

smsgtmac wrote:Your ".1m" edge would have a .1m^2 effective area. Guess what that does to your calculations.

You've posted just a part of paragraph. Please, pay attention to underlined words.
Should I replace S=a*b in formula (5.23) by b*b ? What should I do with lambda squared?
What should I do with sin(x)/x, where x is also dependent on tilted edge "a"?

I'll tell you what it REALLY means:
Independence of frequency, as for sphere, means that we are in this region:
optical.png

For this region RCS is equal to geometric square of object (normal to line of sight)
For shpere it is pi*R^2, and it really frequency-independent.

For tilted plate just its square S=a*b is replaced by S=b*b,
so the result RCS is 0.01 sq.m. - much greater than I calculated.
And with NO placement to (5.23) formula.

I understand that you are trying to fool me (and every forum visitor who read this).
It is just another trap for weak minds.
:notworthy: :notworthy: :notworthy: :notworthy: :notworthy: :notworthy: :notworthy: :notworthy: :notworthy:

smsgtmac wrote:Curved surfaces require treating specular diffraction of RF energy as a return from striking a "specular point" (Knott et al, P. 549). I have no desire to spend my time explaining what this means, even if we just covered what we could find in the public domain.

I tell you - this is Huygens–Fresnel principle I've mentioned.

smsgtmac wrote:At aspect angles greater than ~40 degrees, the relevance of the theory of physical optics “gives way” (Knott et al, P. 232) to edge diffraction

“4?” You cannot treat the RCS of the canopy as an independent RCS number if it is integrated into the overall design such that the canopy is properly ‘blended’ into the rest of the aircraft.
“5?” A good LO aircraft has excellent impedance matching between its constituent components and to the airstream.

Two statements contradicting each other? I dont know how is this logic fallacy (or trap) called, maybe you know better.
Just decide first - Edge diffraction or integration into design with no discontinuities?

1. I calculated RCS without edge diffraction which of cause can be added too.
2. Do you mean this:
discontinuity.png

It's just ridiculous.
It is true for tooth-like edges between parts of airframe, but not for canopy.

Now, go read up on this stuff. I dont know who is troll here.

BTW, if it may help, I am 36, live in Belarus, have a family, 3-room apartment, 2 dogs, and I drive a 17-yo peugeot.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 25 Nov 2014, 10:14
by mityan
KamenRiderBlade wrote:But to align your radar with a moving aircraft in that manner is a next to impossible task, so the risk is negligible.

This is a case when two counterpart are at same height. For long ranges the position of ground radar or position of airborne radar - down or up 10 km - will give small difference in angle.

KamenRiderBlade wrote:If you think you can outdo the world's leading defense contractors with cursory knowledge, you must be mentally challenged.

smsgtmac loves logical fallacies. This is Appeal to Authority.
http://www.nizkor.org/features/fallacies/appeal-to-authority.html

BTW.
you are not going to get much if any RF sources reflected back to the source unless you're directly under or above, and realistically, that's not going to happen.

So you dont believe David Fulghum from Aviation Week, who asserted that -40 dBsm is an ALL-ASPECT RCS?

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 25 Nov 2014, 11:56
by KamenRiderBlade
mityan wrote:This is a case when two counterpart are at same height. For long ranges the position of ground radar or position of airborne radar - down or up 10 km - will give small difference in angle.
It would still require that the
original position of the opposing radar be in the right place. And a small difference in angle is all it takes to make the radar refraction go in the wrong direction and away from your radar dish.


mityan wrote:smsgtmac loves logical fallacies. This is Appeal to Authority.
http://www.nizkor.org/features/fallacies/appeal-to-authority.html

The same can be said about you.


you are not going to get much if any RF sources reflected back to the source unless you're directly under or above, and realistically, that's not going to happen.

So you dont believe David Fulghum from Aviation Week, who asserted that -40 dBsm is an ALL-ASPECT RCS?[/quote]
The entire lot at Aviation Week is very suspect from the beginning. The fact that they still employ Bill Sweetman, associate with David Axe, the rest of the folks there have lost a lot of credibility IMO due to the company that they choose to keep.

David Fulghum is no exception to this rule.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 25 Nov 2014, 12:20
by mityan
KamenRiderBlade wrote:
mityan wrote:smsgtmac loves logical fallacies. This is Appeal to Authority.
http://www.nizkor.org/features/fallacies/appeal-to-authority.html

The same can be said about you.

I'm based on literature, it's different. :)

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 25 Nov 2014, 12:41
by KamenRiderBlade
mityan wrote:
KamenRiderBlade wrote:
mityan wrote:smsgtmac loves logical fallacies. This is Appeal to Authority.
http://www.nizkor.org/features/fallacies/appeal-to-authority.html

The same can be said about you.

I'm based on literature, it's different. :)


I don't trust your interpretations on your literature.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 25 Nov 2014, 16:02
by hornetfinn
http://www.jatm.com.br/papers/vol4_n1/JATMv4n1_p25-32_Indoor_Radar_Cross_Section_Measurements_of_Simple_Targets.pdf

Figure 7 presents the RCS values in dBm of flat plate as a function of aspect angle. Figure 8 presents them in square meters. Those calculation seems to indicate that such a flat plate would have the lowest RCS value at aspect angles higher than 30 degrees with 60 degrees being rather optimal. The higher aspect angles give about 17 to 19 dBm smaller RCS than perfectly perpendicular flat plate. So that means that if we simplify the canopy to tilted flat plate, we will get about 50 to 80 times smaller radar cross section in square meters than the actual area of the plate. Give the canopy decent radar absorbing treatment and the RCS of the canopy will be extremely small.

Another source: https://www.ee.washington.edu/research/ersl/Documents/Paper/2004%20Multple_Scattering_Effects_RCS,%20WRM.pdf

This gives pretty much the same values.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 26 Nov 2014, 06:34
by delvo
smsgtmac wrote:I've adopted the late, great, Professor J. Rufus Fears' convention of using the Greek phonetic spelling of 'Hybris'.
That's neither Greek nor phonetic. It's a mistaken and misleading Romanization of a word whose original spelling isn't even in this alphabet, and whose pronunciation is not what that spelling looks like to modern English-speakers. Spelled phonetically in the Latin alphabet (ours), it would have a "u", not a "y", because the sound is actually more like in "flu" or "flew", not "fly". Spelled in the Greek alphabet, which the letter "y" was meant to evoke to Latin audiences because their established familiar alphabet had no such letter, the whole word would look different, not just one letter.

The letter "y" was a late addition to the Roman alphabet, based on the Greek letter upsilon, the equivalent of Latin "u". It was entirely redundant to "u", representing exactly the same sound, and had no use in Latin spelling other than in the transliteration of Greek names & terms to make them look more foreign and exotic, like the fake-foreign elements in the modern English name "Häagen-Dazs". Later, when the letter "y" was established as part of the Latin alphabet but its sound-value shifted so it wasn't the same as "u" anymore, any word from earlier times that kept it would get mispronounced (like "hyper/hypo", which were pronounced "huper/hupo" originally, before the pronunciation got influenced by the lingering "y"-spelling), and any whose original pronunciations were preserved needed to use "u" for that phonetic spelling (like "hubris").

Of course, that got further complicated by the modern English habit of pronouncing "u" as "yu" even in words that weren't like that originally, but the fact remains that just replacing "u" with "y" in a word of ancient Greek origin does not make the spelling either Greek or phonetic.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 27 Nov 2014, 21:42
by smsgtmac
mityan wrote:
smsgtmac wrote:No....Not Even Close.
The ‘flat plate’ equation you present is not relevant to a flat plate tilted at the angle indicated. If you had read the paragraph after that equation in your source, you would have read this:
formula_again.png

Note the highlighted point of interest.

What does it mean? Let me explain.
If we have a laboratory, a set of devices to generate and measure a signal of interest, and we are going to perform some precise measurements, we should at first calibrate our devices. It means the measurement of exactly known pattern.
Let's take a closer look to the formula - biuld a dependency on freq (6-15 GHz) and in wide angle span:
formula_dependence.png

So, indeed, we can calibrate ony in very narrow angle span near normal line.
But stop now!
Why we are talking about calibration at all? Who cares of it?
Does it mean that the formula is wrong or has a limited usage (i.e. rcs of plane undergoes different laws)?
NO.
So what was that? What kind of logical fallacy -
Composition fallacy - http://www.nizkor.org/features/fallacies/composition.html
or Red Herring ? http://www.nizkor.org/features/fallacies/red-herring.html

Go further.
formula_dependence2.png

smsgtmac wrote:Your ".1m" edge would have a .1m^2 effective area. Guess what that does to your calculations.

You've posted just a part of paragraph. Please, pay attention to underlined words.
Should I replace S=a*b in formula (5.23) by b*b ? What should I do with lambda squared?
What should I do with sin(x)/x, where x is also dependent on tilted edge "a"?

I'll tell you what it REALLY means:
Independence of frequency, as for sphere, means that we are in this region:
optical.png

For this region RCS is equal to geometric square of object (normal to line of sight)
For shpere it is pi*R^2, and it really frequency-independent.

For tilted plate just its square S=a*b is replaced by S=b*b,
so the result RCS is 0.01 sq.m. - much greater than I calculated.
And with NO placement to (5.23) formula.

I understand that you are trying to fool me (and every forum visitor who read this).
It is just another trap for weak minds.
:notworthy: :notworthy: :notworthy: :notworthy: :notworthy: :notworthy: :notworthy: :notworthy: :notworthy:

smsgtmac wrote:Curved surfaces require treating specular diffraction of RF energy as a return from striking a "specular point" (Knott et al, P. 549). I have no desire to spend my time explaining what this means, even if we just covered what we could find in the public domain.

I tell you - this is Huygens–Fresnel principle I've mentioned.

smsgtmac wrote:At aspect angles greater than ~40 degrees, the relevance of the theory of physical optics “gives way” (Knott et al, P. 232) to edge diffraction

“4?” You cannot treat the RCS of the canopy as an independent RCS number if it is integrated into the overall design such that the canopy is properly ‘blended’ into the rest of the aircraft.
“5?” A good LO aircraft has excellent impedance matching between its constituent components and to the airstream.

Two statements contradicting each other? I dont know how is this logic fallacy (or trap) called, maybe you know better.
Just decide first - Edge diffraction or integration into design with no discontinuities?

1. I calculated RCS without edge diffraction which of cause can be added too.
2. Do you mean this:
discontinuity.png

It's just ridiculous.
It is true for tooth-like edges between parts of airframe, but not for canopy.

Now, go read up on this stuff. I dont know who is troll here.

BTW, if it may help, I am 36, live in Belarus, have a family, 3-room apartment, 2 dogs, and I drive a 17-yo peugeot.

Mityan! You came back!
Yes, I do have a talent for ferreting out logical fallacies (decades of test design experience will do that for you). Your latest reply contains at least five (In order: Red Herring, Non-Sequitur, Non-Sequitur/Burden of Proof, Red Herring via False Dilemma, and a Fallacious Appeal to Ridicule). But as today is our (American) day of Thanksgiving, I am not inclined to spend it ‘Fisking’ your claims.
Instead, for now I refer all to Chapter 5 of Knott etal’s Radar Cross Section, which fortunately is found in its entirety here.

For reference by others, I may later post relevant excerpts, or perhaps just the chapter summary with emphasis added to significant points. The chapter clearly exposes Mityan's contretemps on HF RCS as overly-simplistic, while also supporting my, and several others’ here, observations/points about the same.

Happy Thanksgiving everyone!

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 27 Nov 2014, 21:44
by smsgtmac
delvo wrote:
smsgtmac wrote:I've adopted the late, great, Professor J. Rufus Fears' convention of using the Greek phonetic spelling of 'Hybris'.
That's neither Greek nor phonetic. It's a mistaken and misleading Romanization of a word whose original spelling isn't even in this alphabet, and whose pronunciation is not what that spelling looks like to modern English-speakers. Spelled phonetically in the Latin alphabet (ours), it would have a "u", not a "y", because the sound is actually more like in "flu" or "flew", not "fly". Spelled in the Greek alphabet, which the letter "y" was meant to evoke to Latin audiences because their established familiar alphabet had no such letter, the whole word would look different, not just one letter.

The letter "y" was a late addition to the Roman alphabet, based on the Greek letter upsilon, the equivalent of Latin "u". It was entirely redundant to "u", representing exactly the same sound, and had no use in Latin spelling other than in the transliteration of Greek names & terms to make them look more foreign and exotic, like the fake-foreign elements in the modern English name "Häagen-Dazs". Later, when the letter "y" was established as part of the Latin alphabet but its sound-value shifted so it wasn't the same as "u" anymore, any word from earlier times that kept it would get mispronounced (like "hyper/hypo", which were pronounced "huper/hupo" originally, before the pronunciation got influenced by the lingering "y"-spelling), and any whose original pronunciations were preserved needed to use "u" for that phonetic spelling (like "hubris").

Of course, that got further complicated by the modern English habit of pronouncing "u" as "yu" even in words that weren't like that originally, but the fact remains that just replacing "u" with "y" in a word of ancient Greek origin does not make the spelling either Greek or phonetic.


Delvo
You’re right. I was mis-remembering Fears’ explanation of his use of 'Hybris' as being a linguistic ‘translation’ when he actually identified it as a ‘transliteration’. My bad.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 28 Nov 2014, 11:10
by mityan
smsgtmac wrote:Mityan! You came back!
Yes, I do have a talent for ferreting out logical fallacies (decades of test design experience will do that for you). Your latest reply contains at least five (In order: Red Herring, Non-Sequitur, Non-Sequitur/Burden of Proof, Red Herring via False Dilemma, and a Fallacious Appeal to Ridicule). But as today is our (American) day of Thanksgiving, I am not inclined to spend it ‘Fisking’ your claims.
Instead, for now I refer all to Chapter 5 of Knott etal’s Radar Cross Section, which fortunately is found in its entirety here.

For reference by others, I may later post relevant excerpts, or perhaps just the chapter summary with emphasis added to significant points. The chapter clearly exposes Mityan's contretemps on HF RCS as overly-simplistic, while also supporting my, and several others’ here, observations/points about the same.

Happy Thanksgiving everyone!

Have a nice holidays!

Yeah, it would be much better to emphasis on actual formulas and their physical meaning. Cause they dont subject to logical traps.
Siplistic point of view does not mean that more precise look at the subject will lead to a completely different values (significantly lower in particular).

BTW, google.books has a limit of pages to be viewed.
Here is a russian website where almost the whole RCS book by Knott is available for free download in PDF (e-mail required).
http://www.twirpx.com/file/305691/
(some chapters endings are lost)

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 02 Dec 2014, 12:18
by popcorn
DId Gen. Bogdan just confirm F-35 has superior stealth vs. F-22?



http://www.airforcemag.com/MagazineArch ... roach.aspx

Hostage caused a stir in late spring when, in press interviews, he said the F-35 would be stealthier than the F-22, its larger USAF stablemate. Conventional wisdom had pegged the F-22, with its angled, vectored-thrust engines, as a stealthier machine than the F-35. Hostage also said the F-35 would be unbeatable when employed in numbers, which is why the full buy of aircraft is "so critical."

"I would say that General Hostage … is accurate in his statement about the simple stealthiness of the F-35 [with regard] to other airplanes," Bogdan said in the interview. The statement was accurate for radar cross section, as measured in decibels, and range of detectability, he said, and he scoffed at the notion that anyone can tell how stealthy an aircraft is just by looking at it.


The comment about the effectiveness of F-35s together "has less to do with stealthiness and more to do with overall survivability," he said.

"We are going to ask the F-35 to do things that no other airplane—fourth gen or otherwise—is going to be able to do in the future," he stated. For some of those missions, "it would be much better to do it with more than one F-35."

Besides their stealthiness, the F-35s share information and can perform electronic warfare, electronic attack, and cyber missions.

"When you put two F-35s in the battlespace, … they become even more survivable when they do it together," Bogdan asserted. With two or more, "the sum of the parts is greater than the whole," especially when the aircraft are teaming up "from different parts of the airspace, on the same targets. It becomes quite effective."

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 02 Dec 2014, 20:39
by KamenRiderBlade
popcorn wrote:DId Gen. Bogdan just confirm F-35 has superior stealth vs. F-22?



http://www.airforcemag.com/MagazineArch ... roach.aspx

Hostage caused a stir in late spring when, in press interviews, he said the F-35 would be stealthier than the F-22, its larger USAF stablemate. Conventional wisdom had pegged the F-22, with its angled, vectored-thrust engines, as a stealthier machine than the F-35. Hostage also said the F-35 would be unbeatable when employed in numbers, which is why the full buy of aircraft is "so critical."

"I would say that General Hostage … is accurate in his statement about the simple stealthiness of the F-35 [with regard] to other airplanes," Bogdan said in the interview. The statement was accurate for radar cross section, as measured in decibels, and range of detectability, he said, and he scoffed at the notion that anyone can tell how stealthy an aircraft is just by looking at it.


The comment about the effectiveness of F-35s together "has less to do with stealthiness and more to do with overall survivability," he said.

"We are going to ask the F-35 to do things that no other airplane—fourth gen or otherwise—is going to be able to do in the future," he stated. For some of those missions, "it would be much better to do it with more than one F-35."

Besides their stealthiness, the F-35s share information and can perform electronic warfare, electronic attack, and cyber missions.

"When you put two F-35s in the battlespace, … they become even more survivable when they do it together," Bogdan asserted. With two or more, "the sum of the parts is greater than the whole," especially when the aircraft are teaming up "from different parts of the airspace, on the same targets. It becomes quite effective."


The man is on top of the inside track and pretty much the head of the program.

If anybody knows the real RCS numbers, it's that man, General Bogdan.

If he says it's lower than the F-22, I can believe his words. The advances in technology between the F-22 and F-35 development on top of knowledge gained from the F-22 would've pushed Stealth technology further ahead. It makes sense that the F-35 would end up being stealthier than the F-22 in the long run given that:

1) F-35 is newer than the F-22, ergo the latest in Stealth / Aerodynamics / Aerospace engineering is put into 1 plane
2) Lockheed Martin learns from any mistakes or weakness in Stealth design of the F-22 and fixes it for the F-35
3) More powerful computers allow better design of Stealth fighters and a better overall aircraft

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 03 Dec 2014, 09:55
by mityan
But what does it mean?
The metal marble is much bigger than it was considered?
Or F-35 has a pin-head RCS?
pin.jpg

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 03 Dec 2014, 12:54
by hornetfinn
There are many sizes of marbles. Maybe F-22 has an RCS of a large marble and F-35 a small marble. Large marbles are larger than golf balls or even tennis balls, so the metal marble reference can mean a lot of things. What's important is that both have very low RCS in any case compared to any previous fighter jet.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 04 Dec 2014, 03:34
by popcorn
Definitely not beachball-sized though... paging Peter Goon :D

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 07 Dec 2014, 08:23
by mityan
popcorn wrote:DId Gen. Bogdan just confirm F-35 has superior stealth vs. F-22?

By the way, it is very interesting, what would Dr. Carlo Kopp say about it. :D

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 09 Jun 2019, 15:06
by taog
Hey guys, recently I receive some information of JSF program from others. One is a picture comes from LM's paper ("F-35 Program History – From JAST to IOC") which shows that during the development of JSF projram (before SDD phase), there had a requirement for low band RCS reduction. (Highlighted with a red box in the figure )

Image

Also, there was an article published on Aviation Week in 1999/2, "JSF Reflection Is Golf Ball-Sized", which not only stated that the requirement of the RCS spec. for JSF was -30 db but also mentioned that the JSF would have the low-observability ability in VHF band. So it seems like the military, at least, had once considered the VHF RCS reduction for the JSF program (maybe happened at JIRD-1 or -2 or -3 ? Configuration 220-2 was the baseline design when JIRD-1 was released.). Do you guys have any further information about this or whether this low band RCS reduction requirement was retained or dropped after the program entered SDD phase ?

Image
Image

PS. what does "in a 40-deg. vertical fan" mean in the below picture ?

Does there have any report or rumor mentioned the JSF RCS spec. earlier than that article (1999/2) ?

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 09 Jun 2019, 19:22
by wrightwing
Reports from 1999 and earlier, are way out of date. In recent years, it's been revealed that the F-35 has a lower RCS than the F-22. I'd also recommend googling LM"s CNT RAM patents, to get an idea of the frequency range, that it's effective against.

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 10 Jun 2019, 07:15
by zero-one
wrightwing wrote:Reports from 1999 and earlier, are way out of date. In recent years, it's been revealed that the F-35 has a lower RCS than the F-22.


I thought the general consensus was that they are roughly the same. -40 dBm2
While other sources say the F-22 is stealthier from certain angles.

https://www.globalsecurity.org/military ... ft-rcs.htm
From the front, the F/A-22's signature is -40dBm2 (the size of a marble) while the F-35's is -30 dBm2 (the size of a golf ball). The F-35 is said to have a small area of vulnerability from the rear because engineers reduced cost by not designing a radar blocker for the engine exhaust." [Aviation Week & Space Technology; 11/14/2005, page 27]

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 10 Jun 2019, 07:48
by taog
zero-one wrote:
wrightwing wrote:Reports from 1999 and earlier, are way out of date. In recent years, it's been revealed that the F-35 has a lower RCS than the F-22.


I thought the general consensus was that they are roughly the same. -40 dBm2
While other sources say the F-22 is stealthier from certain angles.

https://www.globalsecurity.org/military ... ft-rcs.htm
From the front, the F/A-22's signature is -40dBm2 (the size of a marble) while the F-35's is -30 dBm2 (the size of a golf ball). The F-35 is said to have a small area of vulnerability from the rear because engineers reduced cost by not designing a radar blocker for the engine exhaust." [Aviation Week & Space Technology; 11/14/2005, page 27]


But at final, the F-35 have added the blocker.

In 2001, a report ("Lockheed Martin touts JSF stealth improvement", Aviation Week) said that the F-35 for cost saving, didn't use the blocker. (Also, it mentioned in 2001, LM announced the F-35's RCS already superior to the -30 db. )
Image
Image

But in 2010, there was a news:
"Pratt points out that the F119 and F135 are the only production engines with stealthy augmentors. Their design eliminates conventional spray bars and flame holders and integrates multi-zone reheat fuel injection into curved vanes that block the line-of-sight to the turbine. "

Also, in the recent PDF, F135 truly have the blocker.

Image

Re: F-22 and F-35 RCS revealed by USAF

Unread postPosted: 10 Jun 2019, 09:20
by wrightwing
zero-one wrote:
wrightwing wrote:Reports from 1999 and earlier, are way out of date. In recent years, it's been revealed that the F-35 has a lower RCS than the F-22.


I thought the general consensus was that they are roughly the same. -40 dBm2
While other sources say the F-22 is stealthier from certain angles.

https://www.globalsecurity.org/military ... ft-rcs.htm
From the front, the F/A-22's signature is -40dBm2 (the size of a marble) while the F-35's is -30 dBm2 (the size of a golf ball). The F-35 is said to have a small area of vulnerability from the rear because engineers reduced cost by not designing a radar blocker for the engine exhaust." [Aviation Week & Space Technology; 11/14/2005, page 27]

Depending on the source, they may be better than -40dBm2. The golfball/marble analogy is out of date, too.