S-75M (Sa-2E) V-755 missile performance and caracteristics

[Rex854Warrior]

Hello,

 

 

I have recently noticed that the V-755 missile fired by the Sa-2 we have in DCS has a habit of missing fast movers at high altitudes flying straight at the SAM site (40k feet, mach 1) because it is unable to pull enough Gs (2G max) to make the intercept at least until it's too late to pull more (it did ping to around 8G just before missing by around 100m, track is attached) .

 

Now that seemed a bit odd so I dug a bit and found some very interesting, well written, thorough and complete (most of the time, depending on the available data on a particular SAM) documents about multiple Soviet SAM systems which I will link in this post. All of the sources are cited in the said documents.

 

From an initial analysis this looks like an issue with the PN coefficients because neither the document or the game shows that the missile would not be capable of reaching the target if it maneuvered as hard as it could (which I see no reason why it wouldn't in the final stages of the intercept).

Anyways I will let the devs take a look at the data and the documents and figure how to fix this odd behavior properly but I did try and modify the PN coefficient (increased from 0.5 to 1 in the DCS\CoreMods\tech\TechWeaponPack\Database\vehicules\SAM\S75_Launcher file) used when the missile is within 1000m of the target and it fixed the issue in this particular scenario. HOWEVER, don't stop reading here ^^, the missile would greatly benefit from more PN coefficients and more adjustements.

 

I think that is about it. Thanks for reading.

 

Sincerely,

Rex

Documents 1.zip

Documents 2.zip

Documents 3.zip

TestSa-2.trk

[Krippz]

Great post!

[nighthawk2174]

Not a new issue but I'll dredge up my post and others

https://forums.eagle.ru/newreply.php?do=newreply&p=4052530

Now I know that the previous thread on the SA2 guidance has been marked as [no bug] but i'm still worried about the SA2's performance. I don't expect anything to be done immediately, hec, I don't expect anything will be done for years but I do hope that ED will at least consider adding the proxy fuze code to the S75launcher.lua (a simple task) and move improving the SA2 up the priority list.

 

For reference this was inspired by this thread:

https://forums.eagle.ru/showthread.php?t=250138

and my response to this was:

 

 

 

 

The Sa2 has several different guidance modes, all of which are fundamentally under the umbrella of command guidance.

 

 

 

 

 

 

 

In short command guidance is where a tracking radar locks onto and tracks a target. It then calculates an intercept point. Once the missile is launched it is connected to the central computer via a missile uplink. In the SA2 this uplink is in the but of the main body. Additionally this antenna is blinded for the duration of the boost stage and as such it should not do any maneuvering at all during this time. Once the boost motor falls away and the uplink is established the computer will track where the missile is and where the target is and compute sterring corrections which will then be sent up to the missile. The missile itself has no ability to detect the target. This is why missile uplink jammers were so effective in vietnam, once the uplink is servered the missile goes balistic. Additionally there was the unintended sidefect of this often caused the missile to explode!

 

 

Half Lead:

 

 

 

 

 

 

Three Point:

 

 

This is basically what we have now, it a pure pursuit fly out and is really only used against jamming targets or if ranging data is unreliable.

 

 

 

 

Other Special Modes:

 

 

yes... this is a ground attack mode :P

 

 

 

 

The Necessity of Proximity Fuzes:

 

A BIG problem here is the lack of the proxy fuze code. Missiles like the SA2 often lacked the precision and hence ability to get direct hits unless it was a very large bomber like target. This is why missiles like the sa2 and sa3 had very large warheads and proxy fuze ranges. 20-35m on the sa2. So even with the above guidance fixes we would relly need to add the proxy fuze code:

 

Code:

 

fuze_proximity = {
ignore_inp_armed	= 1,
arm_delay			= 3,
radius			= 35,
			},

do note though below 100m ground clutter effectively rendered the proxy fuze unusable for the in game missile type.

 

 

 

 

 

 

https://www.dropbox.com/s/gqnwc2qhbsxujtx/SA2-headon.trk?dl=0

https://www.dropbox.com/s/p4kyccpuvsawjia/Tacview-20190930-230831-DCS-SA2Test%20.zip.acmi?dl=0

 

 

It is no secret the SA2 has just about no ability to hit anything. As a test I had two F14's fly at 35k ft M1.0, no ecm, no countermeasures, no maneuvering, and where flying right at the SA2's. Against 21 SA2 sites which fired a total of 124 missiles for 0 hits. Running this test several times the 14 would occasionally get destroyed but not due to a direct hit or proxy fuze. Rather what happened most often was two Sa2's would run into each other exploding and killing the F14. Less common a missile would pass near the F14 then warp into the jet exploding.

 

This however only occurred when I placed more than 6-8 SA2 sites if below this number this is what generally happened:

 

Now with the above in mind. The Sa2 near impact can be seen pulling as much as 16g's, which is far above the maximum value of 6g's. Documentation indicates that at 35k feet the SA2 should have no more than 4-5g's. Meaning those few times it did happen to kill the F14 would most certainly not happen should this fix ever be added. My hope is that ED will take a look at adding the proxy fuze code and latter down the line improving the kinematic accuracy and guidance of the missile.

 

 

fuze_proximity = {
ignore_inp_armed	= 1,
arm_delay		= 3,
radius			= 35,
			},

 

 

https://forums.eagle.ru/showthread.php?t=259209

https://forums.eagle.ru/showthread.php?t=250138

[Tyrannik]

Bump.

 

Please ED, this really should be an easy fix. This SAM is absolutely useless in its current state, and I absolutely refuse to believe that it's working as intended.

[Tyrannik]

Bumping for visibility.

[GumidekCZ]

Similar topic already marked as [ALREADY REPORTED], your words been heard, hopefully will be fixed and improved soon.

https://forums.eagle.ru/topic/253259-already-reportedsa-2-misses-100-of-the-time-due-to-lag-pursuit/?tab=comments#comment-4485567

 

Edited December 21, 2020 by GumidekCZ

[nighthawk2174]

I would temper your expectations though it's been marked as reported basically since it came out and still not much.  Was even marked as no bug for a while too.

[GumidekCZ]

14 hours ago, nighthawk2174 said:

I would temper your expectations though it's been marked as reported basically since it came out and still not much.  Was even marked as no bug for a while too.

You are just kidding me, not true, no-one can be such a "..." to mark this [CORRECT AS IT IS]

If mention only single script value of fuse distance of only 20m, its more than clear, than there is something terribly wrong. Which have been already prooved by track files.

Will not talk here again, about possibility to change fuse setting inflight / three flypath guidance method (pure, half lead, K method) / leathality of warhead fragments at certain distances / ability to track and guide a missile on target after beeing lost for a moment. - Many of these things is not problem of only SA-2, but also most of other SAM systems in game.

Edited December 22, 2020 by GumidekCZ

[nighthawk2174]

I'll also just post my post again

 

 

[TotenDead]