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Thread: Rafale 2018 Thread: Europe's best Eurocanard

  1. #91
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    What bothers me still is that by that equation, I could have a radar with a detection range of around 780 km with 5 time the number of modules and still requiring the same power. With today's electronic that would make deriving from fighter AESA , attractive bizjet AWACS and very mobile SAM long range radar solutions, very attractive. Not cheap ,but reliable and with minimum specific R&D . And yet this does not seem to happen.
    You don't. The more module you have, you will need more input power. I don't understand how you can come to the conclusion that more TRM can use same amount of input power.

    The equations assume same module properties.. like say 10 watt of emitted power. While the power required by the module would roughly depend on PAE (Power Added Efficiency) say 25%. So the 10 watt module require about 40 watt. 1000 would need 4000 watt and 10000 would need 40000 Watt of power to get the radar working.

  2. #92
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    The equation is ok as far as every modules are emitting/receiving. Which is about never the case. Every modules are usually up to receive, but not emitting.

  3. #93
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    That is what I suspected , all things were not equal (or rather the power per module was ,but I am interested by constant total power ).
    What I try to figure out is for a given power which can be produced and made available to the radar, what would be the performance improvement of the radar with x% more modules.
    Aperture would be bigger and gain better so we can expect some better performance . But there I doubt classic mechanical radar equation applies for T/R modules. (Each individual modules receive same power flux density no matter how many there are and they remain constrained by their own aperture and gain threshold). Here I would think having more modules only marginally affect the gain and aperture . Or ?

    With a limited power input , one would of course have to distribute that power over the number of module in emit. Hence less power per individuals the more modules there are. But one can also focus and concentrate that power on a narrower beam the more modules there are. But what is best there for the range ?. (assuming no loss ).
    Last edited by xman; 9th February 2018 at 00:06.

  4. #94
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    In theory, the gain will be as described above in the equation. But many other factors will enter into play.

  5. #95
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    The gain of an antenna element is typically proportional to the area of that element.
    The area of the array, and thus gain, will increase proportionally with element count.
    SNR is proportional to Output power x Gain on transmit x Gain on receive, which is proportional to Output power x N on transmit x N on receive.
    For infinite input power and cooling the Output power is proportional to the number of elements. Hence, SNR is proportional to N^3 (for equal element count on transmit and receive).
    For real life systems there is at least an input power limit so for many systems an increase in the number of elements may actually reduce your output power (you will 'waste' additional power on control logics, etc).

    It is normally the highest frequency and the maximum scan angle that determines the maximum element distance in the array (the grating lobe criterion).
    For quadratic grids and 90 degree scan angle the maximum distance is approx. 0,5 lambda (typically 15 mm on a fighter).
    For equilateral triangular grids the distance can be increased and hence the antenna gain can be kept constant while reducing the element count. This is one of the reasons that Thales positions their elements in a triangular grid.

  6. #96
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    Quote Originally Posted by eagle1
    ATLC in DSI:
    Saying Spectra is better than F-16CJ without HTS is kinda an empty victory, that like claiming you can shot further than an airplane without missiles.
    Quote Originally Posted by eagle1
    another one from captain Romain who wrote a book on rafale in Afganistan:
    Can you post the links or screenshot of this? Because it doesn't look like an official interview on magazine to me.

    Quote Originally Posted by eagle1
    However performance was deemed similar by this Thales project manager. I
    But honestly who would say their product is inferior.
    Quote Originally Posted by halloweene
    Because there are many exchange pilots on FA18 C/D. APG79 is the best known US AESA radar.
    F-18C/D isn't equipped with APG-79.

    Quote Originally Posted by halloweene
    Another physical count on an internet photo?
    No need for that derogatory tone toward photos elements counts, it is at the very least still the count of the physical devices that seen fitted into aircraft nose. I can bet if photos elements count of Rafale shown 1100 or 1200 T/R modules instead then you would be the first to say that it is more accurate than generic value.
    Last edited by mig-31bm; 9th February 2018 at 02:28.

  7. #97
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    The equation is ok as far as every modules are emitting/receiving. Which is about never the case. Every modules are usually up to receive, but not emitting.
    And why not always transmitting ? Naturally for transmit and in fighter radar we have all modules transmitting to make full use of aperture.

    The only exception is if your radar is FMCW with 100% duty cycle, then we have some modules permanently on receive. For fighter radar which never FMCW we don't have 100% duty cycle so there always time where all can transmit and later can receive.

    Quote Originally Posted by xman

    With a limited power input , one would of course have to distribute that power over the number of module in emit. Hence less power per individuals the more modules there are. But one can also focus and concentrate that power on a narrower beam the more modules there are. But what is best there for the range ?. (assuming no loss ).
    How that could be ? You won't make a radar without defining what level of power it needs.

    Range for AESA is of course add more modules. But then if you still revolving around with your confusion without any clear merit on what you actually want to achieve. Then im afraid no equations or person can help you.

  8. #98
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    Thanks drsteel

    This tends to confirm what I thought. while more modules would be better in absolute , there are other parameters coming into play . I can imagine that on designing the radar , considering the power available there is an optimum beyond which adding more modules would only provide limited performance increase, while introducing additional challenge. Hence it is a matter of balancing the number of modules to achieve best possible performance with the T/R characteristic at hands for the possible max power available to the radar for the desired performance. Of course this is constrained by the physical limitations of the aperture.
    The point being , taking the rafale as an example, if there were no limitation of the aperture , would plugging just 500 more modules convert into sensible performance enhancement ? (assuming the backend can cope with those and abstracting other benefits of having more modules such as better agility and easier cooling..etc ).

  9. #99
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    Quote : How that could be ? You won't make a radar without defining what level of power it needs

    Agreed, but the question then become how many modules on the array would provide an optimum performance.
    In transmit , is it more efficient to distribute power over more or less modules to achieve better range ?
    In receive the number of modules in the array (distributed over surface at optimal density for the radar wavelength ) will affect overall radar gain, but by how much ?.
    There are radar equations there, but I was doubtful they applied to array, I had hard time figuring out how come the individual T/R modules which are essentially radio with their own aperture, gain and receiving power thresholds , and their density in the array would not influence the equation for the overall gain of the array. Dr steel explanation above tend to make more sense to me.

    But lets not derail the thread,
    I was essentially reacting to the tendency of more being better in absolute being systematically translated in better raw performance, without all parameters ( power available notably and T/R modules characteristics ) being considered . As I see it there are other benefits and reasons for considering more modules , which are not necessarily about better range and detection performance. As mentioned simpler cooling , better beam forming, shorter latency lower interference in transitioning from transmit to receive......etc. All sensible in their own rights, but not necessarily converting in raw detection range.

  10. #100
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    Saying Spectra is better than F-16CJ without HTS is kinda an empty victory, that like claiming you can shot further than an airplane without missiles.
    You miss the point, the idea was to tell that spectra is integrated into rafale airframe (it is always there whatever the mission) so you always have this capability.

    Can you post the links or screenshot of this? Because it doesn't look like an official interview on magazine to me.
    Indeed, it was a "questions and answers" chat on France Television site with random people. Unfortunately the link is dead now but as it was copy pasted on various forums, the content has been salvaged. However Capitaine Romain is not an unknown pilot as he has published a book on the rafale :

    Click image for larger version. 

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    Last edited by eagle1; 9th February 2018 at 10:02.

  11. #101
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    Skolnik's 3rd Edition of Introduction to Radar System have this radar equation for Active array.

    Notice the N^3 factor which is the number of TRM
    The problem with equations is that one often forgets the reality behind each term.

    Here we have N^3 which should be read as: N˛ x N where the first term is comes from the higher antenna gain and the second comes from the increased power from the extra modules.

    So in theory you can scale to any range but that requires:
    1) infinite power
    2) infinite time for your scanning because you end up with a radar beam that is extremely narrow

    In the real world, a radar is often limited by power generation and especially by cooling. Adding extra modules isn't going to give you jack if you're limited by your cooling circuit. For example, the F-22 radar used to be limited to max one minute at full power before it would overheat.

    In the real world, a radar in scanning mode isn't going to use a very narrow beam because it would take forever for its beam to go over potential targets. A radar that scans a place once every 5 minutes isn't very useful.

    So in terms of detection, extra modules present diminishing returns. Unless you move to a larger platform with more power and multiple arrays for detection and tracking, extra modules aren't that useful.

    Now that doesn't mean that there is no gain, if another platform sends you a track a very sharp beam is an asset. Same thing to help keep the lock on a target that is moving away from you and/or using jamming. For SAR (ground imaging) mode, it's also very useful (better resolution). But the gains are way less than what some basic equation might suggest.

    Anyway, this is supposed to be a Rafale news thread. Discussing for the Nth time its nose size (which is due to the requirement for visibility during carrier landings) is kinda boring. I guess the next topic will be about M-88 engines power...

  12. #102
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    Agreed, but the question then become how many modules on the array would provide an optimum performance.
    In transmit , is it more efficient to distribute power over more or less modules to achieve better range ?
    What is your optimum performance ? What you want to achieve ?

    You can easily play with the fourth root rules to see what kind of improvements you seek. If you want a full equation then you have to consult K Barton's book "Equations for Modern Radar"

    What do you mean by distributing power over more or less ? If you have 1000 modules you will definitely have to scale the power required for it. Less modules mean less power aperture product for active array and you will need alot more power to compensate it.

    In receive the number of modules in the array (distributed over surface at optimal density for the radar wavelength ) will affect overall radar gain, but by how much ?.

    There are radar equations there, but I was doubtful they applied to array, I had hard time figuring out how come the individual T/R modules which are essentially radio with their own aperture, gain and receiving power thresholds , and their density in the array would not influence the equation for the overall gain of the array. Dr steel explanation above tend to make more sense to me.
    Because they are array, they work together. as one to constitute the whole aperture. If you consult to antenna Reciprocity theory you will learn that the gain of antenna in transmit or receive would be same. Except if we have weighting scheme (say Taylor) applied to the antenna to reduce sidelobe during receive or transmit. Then we could have difference in gain in transmit or receive.

    How do you think people out there design radar without radar range equation ?

    and Dr Steel's explanation is basically in line with equations i posted.
    Last edited by stealthflanker; 9th February 2018 at 10:20.

  13. #103
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    Quote Originally Posted by Blue Apple
    The problem with equations is that one often forgets the reality behind each term.

    Here we have N^3 which should be read as: N˛ x N where the first term is comes from the higher antenna gain and the second comes from the increased power from the extra modules.

    So in theory you can scale to any range but that requires:
    1) infinite power
    2) infinite time for your scanning because you end up with a radar beam that is extremely narrow

    In the real world, a radar is often limited by power generation and especially by cooling. Adding extra modules isn't going to give you jack if you're limited by your cooling circuit. For example, the F-22 radar used to be limited to max one minute at full power before it would overheat.

    In the real world, a radar in scanning mode isn't going to use a very narrow beam because it would take forever for its beam to go over potential targets. A radar that scans a place once every 5 minutes isn't very useful.

    So in terms of detection, extra modules present diminishing returns. Unless you move to a larger platform with more power and multiple arrays for detection and tracking, extra modules aren't that useful.

    Now that doesn't mean that there is no gain, if another platform sends you a track a very sharp beam is an asset. Same thing to help keep the lock on a target that is moving away from you and/or using jamming. For SAR (ground imaging) mode, it's also very useful (better resolution). But the gains are way less than what some basic equation might suggest.
    Well naturally i would assume people using the equation to have idea on how it used and what performance they want. Please follow upwards the discussion and you will notice the confusion. and the person specify nothing on what they want to achieve just asking the equation which i provided. There are always real world concern etc... But is there anyone in the world using mathematical equation blindly without being aware of what's behind it.

    I would expect anyone wants to add more modules and with fixed aperture will know that it's either their cooling have limit as PAE for higher frequency module still suck or that unfortunate scanning time as the beam getting narrower and force use of defocusing using weighting scheme.

    If people keep asking without stating actual merit on what they wish to achieve.. what is their definition of optimum ... then isn't it bit insulting to whoever tried to help them understand.

    that's my 2 cents.

  14. #104
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    The draft defense budget shows 28 more Rafale to be procured between 2019-2025, 55 Mirage 2000D to be upgraded.

  15. #105
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    Will those new Rafale be F4.2?

  16. #106
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    Quote Originally Posted by eagle1 View Post
    It has not prevented the rafale to perform well in technical evaluations and exercises, even against design with biger nose, there is so much more. Gripen/F16/SH size like is ok anyway. In some competing designs, bigger can also hide a lack of sofistication where raw power is to compensate for lack of sensor fusion, integrated avionics etc. Or their massive RCS. The more you radiate the more you become visible also, it can play against you. At that game modern RWR with 3D geo-location must be part of the consideration. It has been almost ten years that rafales display long range BVR passive shots with EW only.
    Those are all mediocre competitions done by nation's lacking technical ability or facing sanctions. J-20 has biggest nose and Chinese also built light ucav with boat load of missile capacity.

  17. #107
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    Quote Originally Posted by Loke View Post
    Will those new Rafale be F4.2?
    My understanding is that F4.2 won't be flight tested before 2023 and be ready for production aircraft in 2025 (next six year defense plan).

    If the planned force structure is still 225 combat aircraft, eventually new build Rafale F4 will replace the Mirage 2000D. Anyone know the extent of the upgrades for the Mirage 2000D included in this 6 year plan or how long those aircraft are supposed to serve? Edit, nevermind found it:
    http://www.combataircraft.net/2016/0...o-be-upgraded/

  18. #108
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    Projection of rafale production changes all the time, each time a new French president is elected there is a new white book. I am pretty sure that if France need to buy more rafales to support the whole industry network it will do so. And mirage 2000D will need to be replaced at one point. Bit early to tell but we could even realisticaly see newer rafales replacing older ones in the late 2020's early 2030 waiting for a new program to reach operational stage. With the F4 standard on rail it would still make it a relevant option to bridge the gap with a newer generation system.

  19. #109
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    The draft defense budget shows 28 more Rafale to be procured between 2019-2025, 55 Mirage 2000D to be upgraded.
    Yes, but final number is still 225 between Air Force and Navy. I don't see how it is an increase in the final figure. Yes, FAF will have more aircraft as upgraded Mirage 2000 will be available but not due to these Rafales.
    History and Military Technology blog

    alejandro-8en.blogspot.com

  20. #110
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    I don't think so. They should be the remaining of tranche 4. Probably F4.1
    F4.2 should be tranche 5 (replacement of last M2K)

    Wild guess

  21. #111
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    Quote : What do you mean by distributing power over more or less ? If you have 1000 modules you will definitely have to scale the power required for it. Less modules mean less power aperture product for active array and you will need alot more power to compensate it.

    Seem we are not on the same wave lenght at all , but let me try again .
    If I can generate a max peak power of 10 KW overall to my radar and subsequently elected a design frame to be around 1000 module array ( totally fantaisist figures here, just meant for illustration ) that meet the mimum requirements in detection range ( the only measure I care at this stage ). Now lets imagine I have some latitude as I am not constrained by the size of my array . Would I be better of having 1100 modules instead of the 1000 initially planned to meet the requirements . Would that bring significantly better detection range for my 10 fantaisist Kw overall power . Or in other word , if I have space available , is there a sensible benefit in detection range of having as many modules as possible whatever the power supply is ?.

    and apology , if you felt insulted .As mentionned it was a "naive question".

  22. #112
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    At which point will we see the weapons pods and CFT with RCS enhancement Tranche?

    Is that 5?

  23. #113
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    At which point will we see the weapons pods and CFT with RCS enhancement Tranche?

    Is that 5?
    These are just options, it has not been decided yet. DERIDA demonstrator focuses on stealth & survivability without altering rafale proven aerodynamics. It is quite secretive but other paths could be chosen to reach that goal.

  24. #114
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    Yes fair enough. It could be argued that replacing EFTs with weapons pods and sticking some well designed CFTs on the fuselage, will have very little impact on the performance of the aircraft. If that isn't happening much before 2030, there is no point in a major redesign beyond that is there?

  25. #115
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    Seems the tranche 5 is already in the plans, and it will be "enhanced F4" (F4.2?) however it will be introduced quite late, in the 2030s!

    I must admit, this does not look good for Rafale in Finland. I doubt the F3R will be good enough for the Finns...

    In addition, however, it will in 2023 order a fifth tranche of Rafales, for delivery in the 2030 timeframe. These will be built in an enhanced F4 standard, development work on which will commence in 2018.
    This was also interesting:

    In addition, a new targeting pod will be purchased for the Rafale, with deliveries due by 2023.
    https://www.flightglobal.com/news/ar...-new-s-445762/

    I thought they got a new targeting pod as part of F3R? Or am I mixing up things again!??

  26. #116
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    Quote Originally Posted by Loke View Post
    Seems the tranche 5 is already in the plans, and it will be "enhanced F4" (F4.2?) however it will be introduced quite late, in the 2030s!

    I must admit, this does not look good for Rafale in Finland. I doubt the F3R will be good enough for the Finns...
    No you misunderstand. Those T5 F4.2 deliveries will start in ~2026 and stretch through “the 2030 horizon”, which could mean anything from 2028 to 2030 depending on export orders. Follow-on orders are also likely after 2025 as part of the next 5-year program.

    This is excellent news for Rafale as it nicely sets up continued production beyond 2030, likely in Rafale MLU form.

  27. #117
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    I have a question. On some planes equipped with DDM-NG, there is a little cap at the front of the bar where the DDM-NG is mounted (on fin), with DDM there was not and on some others there is not. Saw it in a Combat Aircraft feature. What is it?

  28. #118
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    It is an antenna, part of spectra. The colour cap is simply different. Or maybe you are talking about Rafale M? (a positioning system for carrier landing is located close)
    Last edited by halloweene; 14th February 2018 at 17:06.

  29. #119
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    This site claims the Rafale costs $115 Million each without initial spares, weapons, ect...

    http://www.business-standard.com/art...1401246_1.html

    The F-35’s affordability is also attractive for New Delhi. In contrast to the bare-bones price of $115 million for each Rafale fighter (with India-specific enhancements, spares, logistics and weapons all extra), the F-35A cost customers $94.6 million last February. Lockheed Martin says it will reduce the cost to $80 million by 2020.

  30. #120
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    @halloweene - The antenna for Spectra is at the back if I'm not mistaken, this is something more akin to a bottle top at the front of the DDM-NG bar and isn't on all Ms or all Rafales. I'll show a picture or you'll probably think I'm mad.

    Click image for larger version. 

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