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Dhimas Afihandarin

@Flankerchan

Sep 20, 2022 • 11 tweets • 4 min read • Read on X

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So Russians using something like Shahed-136, which confirmed few days ago. There might be some other types of drones from Iran but might look it later or maybe if i can have a proper commission for them.

But right now Shaheed or Geran-2 comes first.

#shahed136
#Geran-2

The model are based on available photos and dimension of the drone. Well would be nice if it can be carbon-copy accurate but perspective view just dont give me the option.

The RCS modeling is as usual frontal section 60 by 60 degrees horizontal and 65-110 degrees (45 deg of arc) vertical. Propellers are omitted as well, propeller is likely made out of some form of fiberglass or wood, and those may have even smaller RCS than the drone.

For this modeling the Shahed model will be compared with conventional commercial Mugin/Skyeye Drone previously modeled.

The modeling is done across 36 Frequencies spanning from VHF down to some 36 GHz. The following depicts interaction between the drones and the radiowave. it shows the "spikes"

The main differences apparently from the wing return/wing spikes. The untapered, straight wing of the Commercial drone, stands out, while for Shahed model the wing sweep "moved" the spikes at angle of about 45 degrees. modeling is at 10 GHz

These spikes however are relatively narrow, despite their strength, making it actually hard to detect. Now onto Numbers.

As can be seen. the Shahed model have considerably low RCS in most frequencies modeled. Numerical table are provided for the Shahed model.

This low RCS may make it bit hard to detect. The top end of Ukrainian SAM's the S-300PT/PS, using 5N63 Radar however may be able to detect it at 56 Km, however this distance shorten along with Horizon.

In addition it can be launched en-masse which could outnumber the 6 target channels available for S-300PT/PS. Or be set to fly slower than 125 km minimum detectable speed limit of the S-300PT/PS family.

Guess that's all for now. Hope it can be of some use, feedback are appreciated. and maybe a little bit of support could help me improve the quality of the modeling. One can use following link for support.

Thank you.

ko-fi.com/stealthflanker…

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More from @Flankerchan

Dhimas Afihandarin

@Flankerchan

Oct 15

There are many forms of Radar Range Equation. Including one that you can use to calculate the amount of targets your radar can track.

The equation below show the relationship between Power aperture product/PAG and "radar resources" like -

The update time (basically your beam dwell time if your radar is a fulltime tracking) and the monopulse slope constant, a design dependent but usually taken as 1.2-1.6.

The equation favors High frequency radar, once frequency is selected tho.

The radar tracking performance will depend on its Power aperture product. Which in turn.. bigger radar do better than smaller one. Want more targets to track ? Get moar power or get bigger antenna or both if you AESA as your PAG scales with a power of 3 of your TRM numbers.

Read 17 tweets

Dhimas Afihandarin

@Flankerchan

Oct 8

https://twitter.com/alpha_defense/status/1843718390642528548

Schematics of Virupaksha radar for Indian "Super Sukhoi" Program. Including the TRM's. 30% less than what i estimated back then assuming Uttam's Frequency are used but still massive 2208 TRM's.

https://twitter.com/alpha_defense/status/1843718390642528548

Assuming Bars sized (1 m diameter or 0.78 sqm area) The 2208 element counts and as seen Triangular lattice topology in element placements, assuming 120 degrees scan angle (+-60) will put the frequency in 9196 MHz. Close to Bars and my estimates on J-16 Radar.

That and assume 35% PAE (Power Added Efficiency) for the TRM (typical for class A-Amplifier type) The 10.5 KW cooling available from new VCM cooling Allows 6.6 KW Average power, an increase over 5 KW for Irbis-E. TRM peak power rating will depend on required-

Read 8 tweets

Dhimas Afihandarin

@Flankerchan

Jan 22

Well, some historical account. I am sure everyone that like stealth aircraft already know about "Hopeless Diamond"

I guess imma making one too for "Historical archive" This shape is perhaps the "Ideal" stealth shape. Not a practical flying machine tho.

The story of the hopeless diamond and well the reference image i use can be read here :

It was the first known use of "faceting" method to greatly reduce RCS.f117sfa.org/f117-developme…

As for the modeling. it's as usual "standard" of mine 120 x 45 degrees. The model is pure PEC and based on the 10 ft scale model tested for RCS by lockheed. The frequency is from VHF down to Ka Band (150 MHz down to 35 GHz)

Read 10 tweets

Dhimas Afihandarin

@Flankerchan

Jul 23, 2023

So what if i take the canard away from a J-20 ? Will the RCS got smaller somehow ?

A simple comparison, between both model is done. They're mostly PEC and having same treatment. The purpose is to see what kind of RCS "reduction" coming from removing the canard.

The following is the 2D contour plot presentation for both subjects. 2D contour plot is basically same as the "porcupine" like 3D presentation i do except flattened into diagram and be given clearer angle.

Read 13 tweets

Dhimas Afihandarin

@Flankerchan

Jun 21, 2023

This equation is your friend and will fight for your sanity.

This version of breguet range equation however assume constant L/D, Velocity and Isp. means it's good for a constant altitude and speed scenario.

Isp or Specific impulse are the measure of efficiency of a propulsion. It is the "inverse" of SFC (Specific Fuel Consumption). To convert one to the other you can divide 3600 with SFC. SFC for typical propulsions can easily be found online.

Read 8 tweets

Dhimas Afihandarin

@Flankerchan

Jun 20, 2023

I have two aircraft models.. One is Rafale in "BVR murder machine" mode with wing full of Meteors. The other is a J-20 which our South China Sea neighbor have. Which obviously tempting for me to start making something out of those two.

Both types also had undergo some estimates. This is the meteor armed Rafale interact with radar wave.

and this one is the J-20 model. Both model have similar inlet treatment with absorbers lining its wall. But J-20 model does not have RAM coatings atm... in short a PEC model outside. Does it matter ? Yes but you got your first -30-40 dB RCS reduction from shape.