TC12F :
just one remark:
more than once in this very thread, as well as in others, people talk about that “big reflector” that a vertical tail is..it’s been pointed out in this very thread (that’s why I’d like to remind it) that the vertical fin or the rafale is made of EM-transparent materials.. which mans, as far as I understand “transparent”, that radar waves don’t bounce on it but simply go through…
The tail (fin , dérive) is made of carbon fiber , aramide fiber and light aluminium alloy .
http://avionique-systeme.pagesperso-orange.fr/Rafale.htm
http://quedumilitaire.skyrock.com/931071620-Dassault-Rafale.html
The vertical fin , rather large for an aircraft of that size , is indeed made of materials with very low radio refraction .
In the video below , we can see some steps of the tail making , including the resine-composite “criss-cross” , the cooking of the fin and assemblage . Starting at around 4:10 :
http://www.youtube.com/watch?v=douzAeXkjo4
Years ago , some were thinking that the tail was part of the internal fuel but that was wrong . (Aircraft fuel is known to have some radio wave absorbing capabilities ) .
The tail , especialy when seen from the front , is almost invisible to radars .
Of course , the aluminium “squeleton”, while being greatly reduced in size thanks to the quality of the composites , is still detectable at some angles .
Every aircraft with a tail (or two) is having the same problem . RAM is sometimes applies on the edges but it is not the panacea .
The B2 and some futur UCAVs don ‘t have this problem .
Sintra :
If the number of TRM modules and power output dont have a dam thing to do with the detection range of an airborne radar, i guess that the Mitsubishi Melco J/APG-1, the Selex Vixen 500 and the APG-77 have more or less identical tracking capability.
Are you aware that the energy output of an AESA radar are the combined output of the TRM´s modules?
That means that if everything being equal, if you have a radar with 50% more TRM´s, that same radar will have 50% more transmitter power, and just a small look at the radar equation will make it clear how important that diference his.
On top of that you have mentioned another important aspect, signal degradation by heat, and has you have pointed out the answer is a “robust (so bulky) cooling system”, and in order to achieve that you need two things, space and electricity, the last one, on a fighter aircraft is produced by the engines and has a general rule, if everything else being equal, the engine with most thrust will be able to produce more power then/eg electricity, guess wich of those two aircrafts has more “estate room” and wich uses the most powerful engines. Yes, you have guessed.
Well done Sir Sintra ! 🙂 Right on , correct on all accounts .
Personaly , I have been saying for years than the total electrical output of Rafale was the main shortcoming of the aircraft , with regard to futur upgrades .
When they (Dassault-Thalès) say that the RBE2-AA ‘s range can be increased by 10% by reviewing the electrical system , I agree , it is do-able .
What about the futur conformal AESA antenas ? Will we develop better MMICs modules with a better energy ratio to get the power needed to run them ? I would hope so …
Some DGA ‘s papers are talking about it and the way to get the system working . One way is to use lower radar bands (>L-Band) with the conformals AESA antenas which require less power (The good thing is that the L-Band is perfect to detect VLO aircraft :))
Spectra would need to be upgraded to be able to operate with the main AESA sensors and the different wavelength as well as been “radio-cooperative” (understand non-intrusive) with regard to ECMs . We don ‘t want to disturb the conformal arrays and the RBE2 while jamming , to put it bluntly .
I can upload the paper , which is in english , but I am not sure that it is cleared for the public domain … 😮
Cheers .
Quite a nice work Buitreaux .
Give me one from the front if possible , thanks .
bloodshot :
As a suggestion, could you model angular low RCS intakes
This is puzzling me .
I don ‘t understand why some people think that angular shaped intakes (or anything angular for that matter) is the only way (or the best way) to get a low RCS .
From where I stand , it seems that anything which is not angular shaped can ‘t possibly be low observable , which is outright wrong .
So , because the USA , Russia and China are showing angular shaped intakes on their stealth fighters , it must be the only way . :rolleyes:
It is not .
I am NOT comparing the overall RCS of these fighters to the overall RCS of Rafale , obviously . What I want to say is , there are ways to use curves to archive the same result . The “faceted” F-117A is long gone , one just have to look at the fuselage body of the F-22 Raptor and the B-2A to understand the point I am making .
Well designed curves can be used to deflect radar waves away from the emitter as well as limiting the “bouncing” effect .
The problem Dassault faced during the Rafale ‘ making is crystal clear from a French point of view . If we leave aside the money factor , Dassault ‘s bet was to make to best delta-canard fighter they could with outstanding flying characteristics while keeping the RCS as low as possible . The end product fits the bill .
Personaly , I believe that the Rafale ‘s RCS is underated by many . This is something I find rather strange because we have various reports about various encounters in between top fighters like Typhoons vs SU-30s , SU-30s vs Eagles , Eagles vs Typhoons , etc … We have some clues about who ‘s having a good radar , we have some clues about who ‘s having (in general) the first look and who can make the most out of it .
We also have some clues about Rafales vs Eagles , Rafales vs Typhoons , etc …
It seems that the Rafale is detectng its targets first most of the time if not all the time , while the opponent is having difficulties to fire back .
Then , the actual Pesa RBE2 can ‘ t be seen as a “long range radar” . So …
Dassault ‘s design is an outstanding mix in between air flow (lift) and low RCS . Again , look at the picture below a minute or two (or more) and try to be in the radar waves ‘s shoes and in the air flow ‘s shoes :
Notice where the air flow is driven (forced) , like in between the air intakes and the fore-body . Notice the wings-body blending .
Notice the wings leading-edges , starting from the air intakes .
The overall very curvy design has been designed for very good lift as well as for low RCS . Also , RAM has been applies where it counts .
The air intakes obeys to the same rules and they are nothing but simple . They archive 3 goals : excellent airflow at both low and high altitude , excellent airflow at both high speed and low speed , excellent RCS due to curves , S-Ducts and inside RAM coating .
Without moving parts .
Spend a couples of minutes looking at the pic with a critical eye . You ‘ll know what I mean .
This kind of design is miles ahead of the Typhoon ‘s design . It doesn ‘t come as a surprise since the Eurofighter ‘s people were behind Dassault in aircraft making and by quite a way . I know that what I ‘m saying can shock some but it is the truth .
I am not saying that no RCS work has been done on the Typhoon but the knowledge behind the overall design is … questionable at best .
Cheers .
bloodshot :
Read my comment again, I said that the Mirage 2000 and aircraft of it’s generation didn’t benefit from RCS analysis during their development.
Of course they did , you are wrong and I already told you so .
As I said , even the old Mirage III already had a low RCS from design on , as seen here with a Swiss one :
(and with fixed canards already :))
I’m referring to modern signature analysis techniques being used during the development of both the Rafale and Typhoon which were not even considered during the development of the Mirage 2000.
They were . We did not have the tools we have now but maths were already at works .
Haavarla :
Is this something you got from any official manufactor site?
If so can you post a link?
Yes . Thalès always said :
“– Extended range for compatibility with the latest generation long range missiles and ability to detect low-signature targets
– Higher module reliability for reduced cost of ownership (no maintenance required on the active array for 10 years)
– Extended waveform agility, making it possible to acquire submetric synthetic aperture (SAR) imagery while increasing the radar’s resistance to jamming .
The Tranche 4 aircraft were ordered by the DGA in 2009 and will be delivered by Dassault Aviation to the French Air Force from 2013.“
Also :
http://www.thalesgroup.com/Portfolio/Defence/Aerospace_Product_AESARBE2Radar/
and :
http://www.thalesgroup.com/Workarea/DownloadAsset.aspx?id=3416&LangType=2057
bloodshot :
however the Typhoon’s low mounted wing is still blended with the upper fuselage and gives it less lower fuselage area. For an aircraft which normally operates at high altitude having a flatter underside may be more desirable than having a better blended upper wing/fuselage.
The Typhoon ‘s wings are not blended with the fuselage . They merely get rid of the 90deg angle , that ‘s all .
Typhoon having a smoother underside than Rafale ?? 😮
Well , Typhoon :
Rafale :
Cheers .
J-20 Hotdog :
anyone have a good close up shot of the intake? are hte fan blades visible?
The very few radar waves hitting the higher parts of the blades can ‘t bounce back due to the intake ‘s shape and coating .
bloodshot :
It only makes sense to treat the airframe if the increase in RCS in some weapons configurations is comparable to that of the clean airframe. If that’s the case then reducing the RCS of part or all of that weapons load is likely to be more important than whether one aircraft uses a more conspicuous coating of RAM than another.
True . It depends on the weapon load and some work has been done in this matter too .
As an example , the reflected RCS of the Rafale below is probably around 1.5 square meter , which is 10 to 15 times less than a clean F-15 or SU-27 .
Also , a RBE2-AA equipped Rafale with an AtoA weapon load will always get the first active look on any potential threat aircraft and by a good margin .
Cheers .
Another good picture to show the overall design . We can also see some of the sawtooth RAM coating :
Cheers .
Bloodshot :
just to clarify although the Mirage 2000 in the picture you posted is still considered by some to be a modern aircraft, aircraft of it’s generation didn’t actually benefit from RCS testing during their development whereas both the Typhoon and Rafale did.
Completely wrong . What do you think that M2000 is doing in an anechoic chamber ?
Anyway , aircraft manufacturers started to care about RCS since the early sixties . Aircraft like the Lockheed A-12 Oxcart (precursor of the SR-71) or to a lower extent the Dassault Mirage III were designed to keep the RCS low .
To me , the design differences in between the Typhoon and the Rafale are more than obvious . The Typhoon looks like a pipe-tube with big canards and 2 wings stuck on it . It is why I say that they only tried to lower the average RCS with curved S-Ducts (the least they could do seing the huge and badly designed intakes –> wrt RCS) and some RAM paint here and there .
On the other hand , the Rafale ‘s design obeys to some very different rules . I quote :
“”There are a number of basic methods of using geometry to control the way the airframe will reflect and scatters a radar wave .
One is to make the shape flat and at the same time onlique to the incoming waves , so these reflections will never go toward the likely location of a reciever . This is the principle behind the “faceted” F-117A .
Anoher trick is to shape the airframe in such a way that , instead of having the reflected energy scatter in all directions (and thus a portion of it being always picked-up by the enemy radar) , it will bounce back on a very limited number of directions , maybe only one or two .
Another method is to use a compact , smoothly blended external geometry to archive a continuously varying curvature . Most conventional aircraft have constant-radius curves for simplifying the design and manufacturing processes . However , a constant curve is an isotropic scatterer . It
reflects energy equally in all directions .
A varying curvature is similar to a sea-shell helix . The curves have an ever-changing circle radius , as though they are sections of a spiral rather than arcs of a circle , and thus do not reflect energy in the usual predictable way . Rather , they tend to absorb the energy as it scatters towards the interior of the curve itself . This carefull shaping technique can be observe in the overwing engine nacelles of the B-2 , as well as the basic fuselage cross-section of the Rafale .””
Just look again at the Rafale picture posted earlier on or at this :
The front cross-section design and the totally blended curvature design has absolutly nothing to do with the old Typhoon ‘s design .
On the Rafale , everything has been made to deflect the radar waves away from the emitter , especialy from up front and from high-up .
Then , the air intakes design also obeys to the same LO rules . On the Typhoon , the design is poor wrt RCS with many straigh angles , moving parts and flat surfaces :
Compare to this :
When I say that Rafale ‘s RCS is 10 times lower than Typhoon ‘s , I have a case .
Cheers .
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