stealthflanker[USER=”70376″]stealthflanker[/USER]
I know i have missed a good conversation between you and moonlight. But i have some questions to ask. Are decoys only used for deceptive jamming to immitate aircraft targets. Also in regards to self protection jamming, missiles with passive homing will usually go after higher burnthrough jamming targets correct?
Well Decoys are self protection asset. It will not only immitate but also augmenting its signature so it would be bigger and more apparent to hostile than the platform it protects. For case of towed decoy then it may afford jamming function, deceptive one. It will first seduce the missile and then make it miss by jamming or by break lock (shutting down the jammer, forcing the missile to re-acquire the target)
I dont really understand your 2nd question however. But naturally missile with passive homing will go for those having stronger signature.
stealthflankerTalking about engines, is there reason why Sukhoi chose Saturn 117 instead of Salyut AL-31FM3? Apparently FM3 performed better than 117.
Also is it certain Saturn is making izd.30? Wonder why Salyut is being sidelined.
I would say, diversification of production, basically to keep competition when needed as Salyut got big contract already by supplying engine to China. Saturn need to be alive thus why it goes with 117.
Same reason on why in optronics. UOMZ is selected for Su-57 while MiG-35/29M2 etc got NPK-SPP (NIIPP) Optronics instead.
stealthflankerFact though, your misinterpretation of that equation and how it relates to the actual modelling that was performed by the other source really poorly reflects on your understanding of simple maths and common sense.
In your “model” a missile is fired at a stationary target. At 20km from the target the missile (travelling at a unknown speed with unknown deceleration) makes an instant .16 degree turn and travels in a perfectly straight line to the point where it explodes, 57m from the stationary target. You sure you want to go with that? 🙂
Looking forward
If you consider i am misinterpretating the equation, then what would be the correct one ? I’m open to suggestion. Naturally i think you would know and have the better method of calculation which i wish for you to demonstrate. As easy as that. i wonder why you just dont show me the correct way and maybe better equation. That would make our discussion more productive.
The equation that i use is not considering the target is moving or not but rather to demonstrate and estimate the amount of error that could be generated through cross eye jamming. From my understanding Since the missile is basically receiving wrong position of the target and may not be aware of it being jammed it will go just that way and miss regardless of velocity. If it does explode then it will be question on how many fragments may hit the aircraft which a subject for another worksheet.
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@moonlight
Thanks, some note.
I would start by backtracking from the available data before making the calculation of burn through range. If such does not exist however we might use example and “scale it” appropriately. This is an example ARH seeker parameter from Clive Alabaster’s “Pulse Doppler Radar”
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The variables of interest would be the antenna gain (24.3 dB, 269.15 in power ratio), emitted power (50 Watts) and reference range (10 Km) and the reference RCS (10 sqm).
The seeker’s sidelobe. would be about -27 dB (35 cm antenna, in 12 GHz it may contain 544 radiators)
We first need to “scale up” the seeker to the diameter of that the 9B1103M before making any power estimate. To do this we may first estimate the gain of the 35 cm antenna which should be about 30.5 dB (699). Then we can begin scaling up through simple square root rules.
New Range= SQRT(Gainscaled/GainRef) * Reference Range.
New Range= SQRT(699/269.15)*10
New Range= 16.1 Km For 10 sqm target.
Now we have the new range we can work with power. How much we may need for the 5 sqm target. According to the above and 4th root rules. 5 sqm target can be detected in 13.5 km, with 50 Watts of power, but we want 40 Km so.
40=(x/50)^(0.25)*13.5
Where x is our “new power value” can easily put into excel and do what if analysis with result of 3854 Watt or 3.8 KW. You might be surprised but, this is peak power. The average would be much smaller 7% duty cycle which basically put the average power in order of 266 Watt.
Now we have power and estimate of sidelobe. Then we can start calculating the burn through range for the case.
Which in standoff case (the jammer/decoy is in missile sidelobe) would be 4 Km. Self protection basically effective (with burn through range of like 1-6 m)
stealthflankerI see, J/s ratio is required for the initial lure,but after the lure success J/S is no longer important. What happen if the radar reset? such as going offline and online at random?
In case of VGPO or RGPO or false target generation. The radar will lose lock and forced to re-acquire the target. This is when being phased array will provide advantage as its beam steering does not limited by inertia. Most A2A missiles however may “go dumb” and miss after losing lock. The cross eye jamming will direct missile to the place where it shouldnt be.
I combined the chart made by you and garry and try some value.
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Thanks. Might need to repost tho as the file seems to be invalid.
stealthflankerTo the best of my understanding, if the missile hit, then jamming failed to do its job. Therefore, in this case, we can say that radar burn-through (insufficient J/S) effectively defeat cross-eye jamming?
What happens to other forms of smart jamming such as RGPO, VGPO if they can’t reach the necessary J/S ratio
As i previously stated the deception jamming works differently compared to noise.
[ATTACH=JSON]{“data-align”:”none”,”data-size”:”full”,”title”:”cross eye not affected.png”,”data-attachmentid”:3859956}[/ATTACH]
Then it will fail. The jammer failed to steal the tracking gate. Or worse it will turn into a beacon that will improve the victim radar’s tracking capability instead. I dont know if this make sense for you but the required ERP For the jammer to cover the target is needed only initially to “seduce” the radar which then techniques can be employed. If this fail then the radar will basically have only the target and can work as usual.
This is the extent of R-37 seeker that i can find
Thanks, but without transmit power estimate you cannot compute the burn through range.
stealthflankerFeel free to share your worksheet though so we can see the magical “just because” coefficient added to the formula that’s been so prevalent in your other pieces of “work”.
You have it. now it’s your turn. If i were wrong, which part and which one is correct ?
stealthflankerTheir model takes into account closing speed …etc and came up with the same result as yours. So obviously you’ve done the math wrong in order to achieve the same result with a single snapshot distance of 20km.
Fraud?
Well which part ? You can always download my spreadsheet and do it yourself.
If i intend to do fraud etc.. i would not bother sharing source and images of the equations.
Now my question again, do you have comparable model ?
stealthflankerYou haven’t modelled that properly. The miss distance is based on the target missile being at 20km only, 20 seconds away. Any fraction of a degree heading error at that point is very quickly recovered by the missile. You need to model it all the way into the point where human factors come into play…. Eg. The point where the pilot is not getting enough feedback that his jamming is working and has to evade and deploy his decoy.
I would think a pilot would need to see at least a km or 2 of miss distance at 20km range to be confident his jamming is effective.
​​​​​​To take a missile head on and maintain your heading as a missile approaches with .16 degrees angular error would takes balls of diamond.
Well others also seems to arrive at that similar result. Do you have comparable model ? This is from Andrea di Martino’s “Introduction to modern EW System” Artech House. page 330.
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stealthflankerMore or less active cancellation if theta=180?
I wonder. DuPleiss’s paper however states somewhat on that indication if the phase is a perfect 180 deg and amplitude differences between the sources are exactly 1. a radar that use same antenna pattern during receive and transmit (The paper gave example of Conical Scan radar) May not receive return at all.
you can review the respective paper in following :
https://id.scribd.com/document/406512550/DuPlessis-Extended-2009-cross-eye-jammer
stealthflankerOn the assumption that radar burn-through can’t defeat deceptive jamming:
What happens to the Cross eye ECM if J/S can’t reach 20 dB but instead stuck at -5 dB?
The missile will hit. because your jammer can’t seduce the missile to track it and receive the technique. Otherwise if it can somewhat seduce the missile. It will still hit as your jammer cannot produce sufficient angular error.
The following is a calculation for the effect of a cross eye jammer,
First the geometry :
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The nomenclature
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Then the error equation.
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If J/S didnt reach that 20 dB (without gate stealing) or 3-6 with Gate stealing. The error generated (if any) will be very small. The error is measured from the center of the target.
The jammer has following specifications, based on DuPleiss’s Cross Eye jamming analysis :
Amplitue differences between source and target : 0.9 (Ideal is close to 1)
Separation between jammer : Wingspan constrained thus for Su-35 sized aircraft it will be 14m
Radar look angle to target : 1 Degree basically at frontal aspect.
The result with -5 J/S
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About 1.1 meter to the left of fuselage of your aircraft. The missile will blow the left nacelle and maybe the internal weapon bay. Ideally you would want higher J/S to improve error to maybe 4 times of your wingspan so the missile will safely explode or pass your plane without subjecting it to too much debris from warhead explosion.
This is when you have 6 dB of J/S
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The missile will miss by 11.8 m from your centerpoint. better but if it can fuze it might still subject your aircraft to some debris
20 dB
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57 meters of miss distance. This might need very large warhead missile to take you down. typical A2A missile wont have sufficient warhead for this radius.
Simple J/S calculation is unfortunately would not tell you the whole story for deception jamming.
Second question: if ALE-70, MALD-J or GEN-X are used in screen noise mode to shield F-35 from air to air missiles, wouldn’t you agreed with me: “the range which DAS can detect R-37, K-77M will exceed the range which R-37/ K-77M seeker can burn through the noise screen by several orders of magnitude?”
I wonder. I would say it will have longer detection range to those missiles as they move at some M 2-4. The burn through can’t say anything as no real parameters of those decoys nor the R-37 seekers ever released.
stealthflankerWith all due respect, to the best of my knowledge, all jamming techniques need a minimum level of J/S therefor they can all be defeat with burn-through
https://books.google.com.vn/books?id=j7hdXhgwws4C&pg=PA60&lpg=PA60&dq=jamming+and+RCS&source=bl&ots=NKhoq5yHkh&sig=jFNIbx28PCJjFQ5Ovz5lZCczaNM&hl=en&sa=X&ved=0ahUKEwjpwIf1j9LbAhWEppQKHZIfDmoQ6AEIZTAG#v=onepage&q&f=false
No. Self protection jamming such as cross eye, cross pol and stuff like false targets, RGPO, VGPO. Needs specific technique to defeat as they does not brute force but rather replicate your radar signal. If you read my table above, you should be able to realize it. Notice that “High power” in Transmitter related ECCM (means burn through) Only defeat noise jamming.
In Noise jamming situation then you desire burn through range.
stealthflankerFirst and foremost. are you two above there talks about Self protection jamming or Noise jamming ?
The concept of “burn through range” is unfortunately only applicable to noise jamming. Self protection jamming however works in a very different manner and defeated in different way too.
That unfortunately precludes any simplification regarding to potential of self protection jamming. Self protection works by actually replicates the incoming pulse and do some magic trick like RGPO or VGPO., or maybe cross eye in case of Tarantul. Which works well but put constraint in what range the jammer can actually be used as if you activate it too far it will then become a beacon that actually improve enemy radar tracking range.
The following is a simple table regarding ECCM and respective jamming techniques they counter.
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No specific technique however to counter towed decoy, this however might entail higher frequency, thus narrower beamwidth to allow seeker to actually resolve between targets and select one. Or larger warhead of missile.
stealthflankerIn the early 2000s, I remember rumors of China procuring the ‘Kolchuga’ system from Ukraine. I wonder whether the system in pic below (on the right) is related to that?
Those looks more like Troposcatter communication system to me.
stealthflanker[USER=”28771″]TR1[/USER]
Anything new on N036. That part seems to be the most obscure
stealthflankerWell I’m relying on Flateric again atm for that canoe shaped bay.
Might took a while tho before it finally reveal itself, just like when Su-57 first released Kh-59MK2.
Size speculation however is difficult as perspective is a cruel master.
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