Ракеты в DCS

[TotenDead]

2 часа назад, GGTharos сказал:

 

I don't know the antipode effect, at least not by that name.  I'm aware of multi-path problems and scintillation/clutter issues increasing miss distance (in different ways, but still) and of course problems with fuzing at low altitudes (I imagine premature fuzing). 

Well, what i mean by "antipode" is that when the target flies low the radar (either aircraft or missile) gets a stronger return from the "target" that flies directly at the same altitude, but with the minus sign, i.e under the ground. That makes the missile guide itself into the ground instead of flying towards the target

 

2 часа назад, GGTharos сказал:

 

I don't know, I think the FCS handled that and wouldn't give you a DLZ if it believed the RCS was too small, but I'm going off of memory so don't quote me on this.   Because of this there is a practical limit for launching the AIM-54 vs say a fighter, like 50nm TWS and probably around 60 in STT, same with bombers but obviously at longer ranges.  None of this stuff is modeled in DCS, so I don't think HB can make this happen until ED upgrades the radar simulation in general.

 

Ok, i see, thanks

[GGTharos]

1 hour ago, TotenDead said:

Well, what i mean by "antipode" is that when the target flies low the radar (either aircraft or missile) gets a stronger return from the "target" that flies directly at the same altitude, but with the minus sign, i.e under the ground. That makes the missile guide itself into the ground instead of flying towards the target

 

Ok, so a specific case of multipath.  I know it's been a 'issue to be solved' since the 50's for the USN's SAMs.  That is, they were definitely aware of it and they were working on ways to deal with it ... in some cases there are hints on how the accomplished it.  I'm sure there are papers written on it, maybe I'll google them later.  Interesting topics as always but I don't know if we'll see specifics for missiles.

[Max1mus]

On 8/7/2021 at 8:54 PM, Chizh said:

Дело в том что корректно просчитать предельные режимы пусков не просто.

Try 6000m against a target at 50m and mach 1.3 running away (like F-16). The ER launch permission shows at 15km+, the real range is somewhere between 8-9km. Nonmaneuvering target, perfect shot conditions.

[Max1mus]

@Chizh



R-27ER_useless.trk

Why is the DLZ showing 16km here, when the actual NEZ is one third of that? Is that what the ER should be capable of? The problem is the extreme drag when the missile gets under 3000m or so, as you can see in the track.

[Chizh]

No. The issue is the incorrect DLZ calculation.

[BlackPixxel]

@Chizh What is the reason for the R-27 doing pure pursuit in HOJ? That does not make much sense to me.

[tavarish palkovnik]

 

From this literature on page No.200 it is stated: ''main guiding method of R-27R1 is modified method of proportional navigation, also called method of proportional navigation with offset''

 

 

 

So what means ''modified'' in all this ... method with included compensation of linear acceleration of the missile and acceleration of gravity is called modified method of proportional navigation

 

 

 

 

And to understand what it means theoretically and practically and how it influence on trajectory the best is this book of Golubev

 

 

 

Pages 338 and 339 

 

 

 

 

It is same or almost same method as applied is systems S-300V and BUK and we know how missiles 9M82/83 and 9M38 fly, what kind of trajectory these missiles have. It is same with R-27R (ER) for sure. When target and fighter are at same height, there are no chance that trajectory is kinematiclly overloaded horizontal flight, it is with I call it gorka, or loft as some prefer, навесная/верхняя траектория 

 

 

[BlackPixxel]

@tavarish palkovnik

The formulas for the guidance are described quite well in the MiG-29b book.

 

The "modified" part of the proportional guidance is just the addition of a term that depends on the difference of angular rate of the line of sight to the target and the angular rate of the missile itself.

 

I marked in red the term of the normal proportional navigation and in blue the additional term (modification). In formula 4.2 it is for the active homing phase, and in 4.3 it is for the inertial phase.

Look at formula 4.3, because the stabilized antenna and "equisignal direction" makes things easier to understand:

How would they result in the lofted trajectories you described? The missile tries to minimize l_z and l_y, which are the projections of the targets position onto the stabilized seeker plane, and it tries to minimize the derivatives of those values, which are the projection of the velocity of the target onto those planes. For a head on target at same altitude, when those values are 0, the missile will fly a straight path directly into the target, without lofted trajectory.

 

I think the modified guidance from your other documents is something different.

 

 

 

[BlackPixxel]

Also look at this section:

 

The missile adds 0.7 g to the required overload for the two control surface planes to counter the gravity in level flight.

 

0.7 g because the control planes are tilted by 45° (X-shape of the butterfly surfaces when looking at the missile from the front during flight) and the resulting projection of the gravity.

 

So for a target that flies directly to the missile at the same altitude, the missile will have a constant overload of 1 g.

 

Edited August 12, 2021 by BlackPixxel

[tavarish palkovnik]

Yes, you are right. It isn’t same for SAM’s and R-27R.

To be even more complicated, seams R-27ER could be with its own method slightly different to this described for R-27R1

 

 

[BlackPixxel]

34 minutes ago, tavarish palkovnik said:

Yes, you are right. It isn’t same for SAM’s and R-27R.

To be even more complicated, seams R-27ER could be with its own method slightly different to this described for R-27R1

 

 

 

What is the difference? I only saw a different PN coefficient in the homing phase here (3 instead of 4 as in the MiG-29b book).

Edited August 12, 2021 by BlackPixxel

[tavarish palkovnik]

Don’t know @BlackPixxel what more I read about it less and less I understand.

 

What I can’t draw, that I don’t understand  and this I can’t.  
 

Could maybe but can’t accept that rocket of 80’s doesn’t moved a millimeter from others decades before. All right, INS and RK is involved but in same that time in others as well and with much more efficient trajectories.

[BlackPixxel]

I think the use of the antenna as gyro is what prevents it from having better trajectories. It has to fly in such a way that the stabilized antenna points at the target when it is within SARH distance. For a loft it would have to point the antenna below the target during launch, and to then keep an efficient trajectory would require more complicated circuitry.

[tavarish palkovnik]

Если когда нибудь понадобится

 

 

[Чарик80]

А что,кр Х59м перестала перехватываться Патриотом и Хавком?

[Chizh]

12 часов назад, Чарик80 сказал:

А что,кр Х59м перестала перехватываться Патриотом и Хавком?

Не перестала

[Admon]

а можете пояснить, как ракеты с пассивной гсн уходять в последний момент резко на диполи? как это работает с активной понятно, с тепловой тоже(на ловушки)... получается радар самолета переключается с цели на отражатели, но тогда должен терять цель в итоге

[Chizh]

Про какую ракету речь?

Есть трек?

[Admon]

Ракета Р-27ЕР. трека нет только запись с Tacview

https://yadi.sk/i/zNZMvFdWgMNW1w

[Chizh]

Ракеты Р-27Р/ЭР не имеет чистого пассивного наведения. Она всегда требуется подсветки цели БРЛС носителя. При этом также чувствительна к ловушкам попадающим в ДН антенны носителя. При сокращении дистанции она переходит из пассивного наведения на штатное полуактивное.

 

PS

На вашем видео показана тепловая ракета Р-73 ближнего боя.

[Admon]

Ракета там р-27

 

Edited August 23, 2021 by Admon

[Chizh]

А дальность до цели какая в момент пуска?

 

[Admon]

24.5 км

[Chizh]

Тут уже помеха цели должна быть прожжена и ракета наводится в штатном режиме.

[TaxDollarsAtWork]

On 8/5/2021 at 3:39 AM, Chizh said:

Please give a link to this FAQ.