Radar Cross section modeling

[upyr1]

Obviously the RCS is going to be one of the areas where we'll never have something 100% accurate anyhow, what can ED say about how the F-35's RC will be modeled

Would they model the angles or just have stealth mode/ beast mode?

Also would it be possible for someone working on a Su-57, or J-35, F-22 mod to make use of the new RCS model? 

 

[NineLine]

Sounds like something we wold talk more as development unfolds. Thanks. 

[Coyle]

2 hours ago, NineLine said:

Sounds like something we wold talk more as development unfolds. Thanks. 

Will you be revisiting the RCS of other modules, based on aspect and loaded weapons, etc? As it stands our F/A-18 and F-15 in-game have the same RCS. It should instead be just a peg larger or smaller than the viper depending on where you look, though absolutely nowhere near in the same category of an eagle which is what I'm guessing is out of place.

[The Gryphon]

4 hours ago, NineLine said:

Sounds like something we wold talk more as development unfolds. Thanks. 

I am with Coyle here. In order to give F-35 credibility, all aspects of RCS in DCS should be developed futher.

[MiG21bisFishbedL]

3 hours ago, The Gryphon said:

I am with Coyle here. In order to give F-35 credibility, all aspects of RCS in DCS should be developed futher.

Absolutely. If the F-35 is impetus for that core improvement, so be it.

[Dragon1-1]

I'd very much like that, radars had been getting overhauls lately on the emitter/receiver side, we need an overhaul on the target side, as well. The Viper, for instance, can be surprisingly stealthy simply because its frontal cross section is so dinky. Meanwhile, if the F-35 goes into a steep bank and exposes its whole upper surface, it won't be very stealthy no matter what it's painted with. OTOH, the F-15 is pretty easy to lock from any angle. This is where DCS can gain a lot of realism.

[Hobel]

vor 21 Stunden schrieb Coyle:

RCS of other modules, based on aspect and loaded weapons

I don't know exactly how it works in the background, but aspect and proximity to other aircraft have an influence on the RCS. ED,RB,HB modules already take this into account, only payload has no influence on ED modules.

[falcon_120]

I dont see the big fuss with this. You can follow a physic based approach with current simulation capabilities to make a RCS footprint of a plane and assign some estimation based on public information. So if a F16 frontal RCS is something 3.2m^2 an F35C will have in DCS something like 0.05 m^2, and you extend this to other angles and profiles.
In practical terms you might see a F35 (in DCS) with no external loadout and close base door at something like 8 to 18ish nm depending on the radar (eg.APG70 will see it further out than a APG68v5 and so on). That is good enough for us simmers to have fun and try to shot down that sucker before it runs out of missile and go home to rearm and repeat
I also expect planes with modern IRST (eg. Typhoon) to see the F35 on clear days further away than with the onboard radar (probably >30nm depending on factors like use of AB, speed, etc...). In the end, all AF in the world are field IRST tracker on 4th/4.5th gen fighters to reduce the gap with LO fighters, and there is a good reason for that.
 

[TotenDead]

Will the F-35s FSS radome be transparent to other radars of the same band thus significantly increasing its RCS in its forward hemisphere?

[Dragon1-1]

5 hours ago, falcon_120 said:

You can follow a physic based approach with current simulation capabilities to make a RCS footprint of a plane and assign some estimation based on public information.

There's actually public software that can be used to determine RCS of any given shape. The only thing that's classified here is how well the RAM coating actually works, and that would just multiply the RCS from shape by a certain factor. The physics behind radar wave propagation are not classified, nor even particularly complex (though heavy to calculate in real time).

[F-2]

39 minutes ago, Dragon1-1 said:

There's actually public software that can be used to determine RCS of any given shape. The only thing that's classified here is how well the RAM coating actually works, and that would just multiply the RCS from shape by a certain factor. The physics behind radar wave propagation are not classified, nor even particularly complex (though heavy to calculate in real time).

I have to find the source but as I understand Shape is the primary source of RCS reduction while RAM is comparatively minor (it’s not minor but it’s the shape doing the heavy lifting).

[Dragon1-1]

That's true, which is why the exact mechanics of the RAM don't matter, you can just assume some percentage of inbound radiation is absorbed instead of reflected no matter what angle, and this translates to a straightforward multiplication by a ballpark estimation or RAM efficiency. The vast majority of stealth comes from shape, specifically from avoiding presenting a flat surface to the radar antenna. Radar waves reflect just like any other waves, angle of incidence equals angle of reflection. The tricky bit here is hiding the engines and making an intake that will not reflect waves straight back from its inner surfaces while still working well as an intake. This is also why the Viper is a surprisingly good stealth aircraft, despite not really being designed as such: it's physically dinky and its intake has a pronounced S-duct, so the turbine fan (a big honkin' radar reflector) is not directly in view from most angles. The F-35 is different from the Viper in that it also pays attention to reducing side and rear RCS, in addition to hiding the fan disk even better.

[TotenDead]

12 часов назад, Dragon1-1 сказал:

The tricky bit here is hiding the engines and making an intake that will not reflect waves straight back from its inner surfaces while still working well as an intake. This is also why the Viper is a surprisingly good stealth aircraft, despite not really being designed as such: it's physically dinky and its intake has a pronounced S-duct, so the turbine fan (a big honkin' radar reflector) is not directly in view from most angles. 

Цитата

The biggest contribution to RCS on the F-16 is the radar array as it is essentially a flat plate perpendicular to the adversary radar. At 8.15 GHz both the median RCS value (0.9 m2) and average RCS value (1.79 m2) of the F-16 seem to be very close to the 1.2 m2 number often cited in the public sector. 

So, not really stealth

https://basicsaboutaerodynamicsandavionics.wordpress.com/2022/08/17/f-16a-radar-scattering-simulation/

[Dragon1-1]

10 minutes ago, TotenDead said:

So, not really stealth

No, just annoyingly hard to detect, according to pilots who flew against it. In absence of the turbine disc, the radar is probably the biggest contributor here. It's not a Nighthawk, but it's still small enough to show up on radar noticeably later than most other jets.

[TotenDead]

1 минуту назад, Dragon1-1 сказал:

No, just annoyingly hard to detect, according to pilots who flew against it. In absence of the turbine disc, the radar is probably the biggest contributor here. It's not a Nighthawk, but it's still small enough to show up on radar noticeably later than most other jets.

Those pilots must have fought it in a clean configiration. 4-6 AIM-120s must increase its RCS quite a bit

[Temetre]

Am 20.1.2025 um 02:47 schrieb Hobel:

I don't know exactly how it works in the background, but aspect and proximity to other aircraft have an influence on the RCS. ED,RB,HB modules already take this into account, only payload has no influence on ED modules.

 

Some 3rd party devs do fudge numbers to simulate some kind of RCS aspect, but its not that realistic. For example a dev told me HB modules radar just 'assumes' a certain percentage of the planes RCS number depending on front/side/rear/top/down aspect. That assumption is treated the same for every aircraft tho.

Afaik RB and the others did the same. For there to be real improvement, ED needs to create some kind of system/database for RCS, and then the 3rd party devs probably also need to integrate that system into each of their planes.

[Dragon1-1]

12 hours ago, TotenDead said:

Those pilots must have fought it in a clean configiration. 4-6 AIM-120s must increase its RCS quite a bit

IIRC, this was said about the A model, so it wouldn't be festooned with AIM-120s, rather it would only carry four AIM-9s, and probably no bags as well, or just on the centerline. We're also talking aircraft mounted radars of the 80s, so they weren't quite as good as what we have now. It'd still show up noticeably later on modern sets, especially if relatively clean, but it wouldn't be as sneaky as the A could be.

That said, if a modern Block 50 Viper drops both the bags and the air to ground hardware, it could still be pretty sneaky, especially if it has just two AMRAAMs and a pair of Sidewinders.

[F-2]

I’d be interested in hearing how the block 60 fairs as it has a slanted radar.

 

 

On the fighter pilot podcast I think a Raptor pilot even mentioned how illusive the Viper can be on radar.

[TotenDead]

11 часов назад, Dragon1-1 сказал:

 

That said, if a modern Block 50 Viper drops both the bags and the air to ground hardware, it could still be pretty sneaky, especially if it has just two AMRAAMs and a pair of Sidewinders.

Does it have any RAM or radar blocker of some kind inside its air inlet? 

[Dragon1-1]

No (at least the C model and earlier, they might have added something in newer blocks), but it has an S-duct, which, thanks to its angled interior wall, means it doesn't quite count as a flat surface. To figure out how the radar waves actually come out after bouncing around inside, you'd need to use the modeling software, but my intuition is that a lot of them will be scattered, rather than reflected back.

Also note that we're comparing it to other jets of the era, in the vast majority of which the fans are directly in view from the front, with fan blades perpendicular to the airflow to within a few degrees, providing a nice, bright strobe. I'd imagine that Viper is not the only jet that would give interceptors trouble in that area, but merely the most famous. I wonder how the F-104 will look with proper RCS modeling, for instance. It's also diminutive, very pointy, has a small radome, S-ducts (albeit shallower ones than on the Viper) and a limited missile load. I haven't heard too many stories about fighting this one, but I imagine that once properly modeled, it'll appear on the radar quite late, as well. The Viggen might, as well, at least when not loaded for bear. 

[TotenDead]

3 часа назад, Dragon1-1 сказал:

No (at least the C model and earlier, they might have added something in newer blocks), but it has an S-duct, which, thanks to its angled interior wall, means it doesn't quite count as a flat surface. To figure out how the radar waves actually come out after bouncing around inside, you'd need to use the modeling software, but my intuition is that a lot of them will be scattered, rather than reflected back.

 

Not really an S duct

Спойлер

Modern planes have their ducts covered with RAM because it reduces the amount of reflected energy with each bounce And the more there are bounces, the more will be absorbed. If There's no RAM the difference compared to the straight duct would be minimal

Now, why the F-16 was harder to detect then, say, F-15? Well, it's a tiny jet, similar to the MiG-21 when looked from its front. 

 

[NytHawk]

13 hours ago, F-2 said:

I’d be interested in hearing how the block 60 fairs as it has a slanted radar.

 

 

On the fighter pilot podcast I think a Raptor pilot even mentioned how illusive the Viper can be on radar.

Not sure if any Bl.60s got Have Glass, however some entire USAF squadrons have got Have Glass on their Bl. 50s. I have heard of frontal RCS reductions of like 15-30%, which is pretty notable.

[Dragon1-1]

3 hours ago, TotenDead said:

Not really an S duct

It is an S duct, just a shallow one. Either way, you need to be quite a bit under the nose to see the turbine blades. Notice how low is the angle of that picture, and look at the model in DCS if you don't believe me. Also, even without RAM, radio waves are not 100% reflected, and also notice that the interior of the intake doesn't have flat surfaces. This would cause most of the waves to also bounce to the sides, and this would result in them exiting the intake at an angle, not to mention such a complex path would obscure the strobing effect of turbine blades (which is distinctive enough that a mid-2000s Viper can tell which plane it's looking at based on this). You can't really treat an intake like this as a flat surface. MiG-21 doesn't have this advantage because the fan disk on all MiGs prior to -23 is in plain view, or obscured only by the inlet cone, which is transparent to radar anyway because that's where its own radar is.

That would have the effect of making the Viper more visible to SAM radars than to other fighters, because the former would have a good view of the turbine blades. In fact, if you're sneaking up on a fighter, you'd probably want to be below it, to force it to look for you against ground clutter. Aggressor Vipers are well known for their bushwacking abilities, and even against blue sky, you'd often see them late (definitely later than you'd want, given the A model was a vicious WVR combatant).

[upyr1]

On 1/24/2025 at 2:57 PM, Dragon1-1 said:

There's actually public software that can be used to determine RCS of any given shape. The only thing that's classified here is how well the RAM coating actually works, and that would just multiply the RCS from shape by a certain factor. The physics behind radar wave propagation are not classified, nor even particularly complex (though heavy to calculate in real time).

I figured there would be software available to calculate RCS the real issue though is how much computer power it would take to add the algorithms to DCS. 

[TotenDead]

14 минут назад, upyr1 сказал:

I figured there would be software available to calculate RCS the real issue though is how much computer power it would take to add the algorithms to DCS. 

Not much. All parameters would be scripted