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Top speed of the R-27ER

LetMePickThat

By LetMePickThat
in Weapon Bugs

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BlackPixxel

BlackPixxel

Posted
Posted

Regarding R-27ER top speed, it is a bit higher because ED switched to an incorrect rocket motor configuration of just 8 s burntime with a very strong sustain.

 

ED went with a third party source instead of the real manual, so we have just 8 s of burntime instead of 8.6 - 11 s.

  • 3 weeks later...
okopanja

okopanja

Posted
Posted
16 hours ago, tavarish palkovnik said:

Zone of silence…

Another variant to which I gave good rate to be near to that one

 

On one side I would expect the reference where these diagrams came from. 🙂

 

On the other: having accurately modeled rocket would require at least more information on:

1. sensors (majority resolves around: analog/digital)

2. aerodynamics (it appears multiple people did this)

3. dynamics of motor burning (if I read your diagrams correctly this rocket burns in 2 different regimes, which means that current one-burn model is totally wrong).

4. how interception trajectory is calculated.

 

By far I find No. 4 as the most annoying with any of the modeled Russian rockets (E.g. R-27ER/ET, R-77). They fly the simple straight lines, which present us with 2 major issues:

1. running into the ground with intercept point several km bellow the surface. I believe with SA-2/SA-3, they solved in 50s, why the same issue with rocket 70s-80s range? I am sure the professor who solved the issue in 50s would give this as an example to his students 15-20 years later.

2. hit the hill slope. In contrast AIM-120C is in many cases taking slight detour around/over the hill. I believe at least lofting helps here a bit. Not sure if some sort of ground clutter distance measuring also takes place.

 

Now it could be that the originals were equally dumb, but I find it hardly to believe. They have built medium/long range air-to-air missiles before, and surely they would have known about this issues.

okopanja

okopanja

Posted
Posted
1 hour ago, Cmptohocah said:

Where did you guys find the CAD drawings fro the R-27?

Well, its similar approach to what ED did with AMRAAM: reverse engineering. There is a paper you can search for where they considered the kind of rocket fuel, weight aerodynamics etc. You did it partially yourself, why not writting a paper pn R-27 an submitting to ED for peer review?

GGTharos

GGTharos

Posted
Posted (edited)
3 minutes ago, okopanja said:

Likely REDFOR turns into drones.

Do you believe that REDFOR was 'drones' a decade ago in this game?   The missiles were a lot more accurate and didn't lose speed in turns back then.  Let's not get into the habit of doom predictions, because that isn't what's happening here.  We will see what the 120 will do after this change is released.   It will likely require further tweaking, as I personally except it won't handle certain scenarios correctly yet.  But I could be wrong.

Either way, the change emphasizes supporting the missile to TTA at least.

Edited by GGTharos

[sIGPIC][/sIGPIC]

Reminder: SAM = Speed Bump :D

I used to play flight sims like you, but then I took a slammer to the knee - Yoda

okopanja

okopanja

Posted
Posted
14 minutes ago, GGTharos said:

Do you believe that REDFOR was 'drones' a decade ago in this game?   The missiles were a lot more accurate and didn't lose speed in turns back then.  Let's not get into the habit of doom predictions, because that isn't what's happening here.  We will see what the 120 will do after this change is released.   It will likely require further tweaking, as I personally except it won't handle certain scenarios correctly yet.  But I could be wrong.

Please don't get me wrong, I have nothing against realism, but one side is constantly getting upgraded. This is undeniable fact. It is kind of strange to see F-16 fighting on both sides(btw it is on my shopping list).

Still there a lots of improvements potential for REDFOR. Namely rocket guidance and datalinks. Do you honestly think its normal that missile fired at someone at 20k+ ft slams into ground just 1 km ahead the moment he dives to defend (happened to me several times with both R-27ER and R-77, rather comical moments)?

As for oncomming AIM-120c upgrades, they deserve the dedicated topic, and I am looking forward to read how both sides react.

GGTharos

GGTharos

Posted
Posted
17 minutes ago, okopanja said:

Please don't get me wrong,

You're kinda making it easy.

17 minutes ago, okopanja said:

Still there a lots of improvements potential for REDFOR.

Yep, but as you know they're not priority.  And you also know that the missiles in use by player aircraft are old and should not be considered competitive.  Dangerous for sure, but Pk should only be going down.

17 minutes ago, okopanja said:

Do you honestly think its normal that missile fired at someone at 20k+ ft slams into ground just 1 km ahead the moment he dives to defend (happened to me several times with both R-27ER and R-77, rather comical moments)?

Yes.  This is the problem with PN.  Now, is an R-27 smarter than that?  I don't know, I personally assume that there would be something to help there but I couldn't tell you with any certainty.   I can make assumptions based on knowing what a Sparrow would do in some cases.

The 'WCS emulator' can probably be adapted to the Su-27 and MiG-29 in the game to work appropriately for those specific missiles.   And the F-14 really needs this as well (as well as somewhat deeper simulation of the missile's logics, meaning alternative guidance methods for the phoenix).

17 minutes ago, okopanja said:

As for oncomming AIM-120c upgrades, they deserve the dedicated topic, and I am looking forward to read how both sides react.

There will be new ways to exploit the missile - it's capability is going up, but it will still be 'down' from what it used to be a decade ago.

[sIGPIC][/sIGPIC]

Reminder: SAM = Speed Bump :D

I used to play flight sims like you, but then I took a slammer to the knee - Yoda

okopanja

okopanja

Posted
Posted
17 minutes ago, GGTharos said:

Yes.  This is the problem with PN.  Now, is an R-27 smarter than that?

It must be smarter than that, since this issue was first observed and fixed for either SA-2 or SA-3(I found it as a scanned print from the russian book in this forum that likely dates in 60s or 70s). Also this was not a first gen of medium/long range missile developed in Sowiet Union. Typical arguments that I read in this forum on relation analog vs digital. This is purely low level technological base. What matters is what you build on top of your technological base. Beatiful example is the AIM-54A itself which was analog.

 

dundun92

dundun92

Posted
Posted
2 hours ago, okopanja said:

It must be smarter than that, since this issue was first observed and fixed for either SA-2 or SA-3(I found it as a scanned print from the russian book in this forum that likely dates in 60s or 70s). Also this was not a first gen of medium/long range missile developed in Sowiet Union. Typical arguments that I read in this forum on relation analog vs digital. This is purely low level technological base. What matters is what you build on top of your technological base. Beatiful example is the AIM-54A itself which was analog.

 

R-27 uses full PN (no VPN/APN) inside 25km IRL, this is described by relevant MiG-29A manuals. Outside 25km it does use a kind of variable PN constant, but its not for energy retention, its to align the seeker so it can acquire the target; sometimes in this phase the PN is more aggressive than inside 25km. Though overall, id expect the variable PN outside 25km to overall increase energy retention

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nighthawk2174

nighthawk2174

Posted
Posted
4 hours ago, okopanja said:

It must be smarter than that, since this issue was first observed and fixed for either SA-2 or SA-3(I found it as a scanned print from the russian book in this forum that likely dates in 60s or 70s). Also this was not a first gen of medium/long range missile developed in Sowiet Union. Typical arguments that I read in this forum on relation analog vs digital. This is purely low level technological base. What matters is what you build on top of your technological base. Beatiful example is the AIM-54A itself which was analog.

 

As far as i'm aware ED has relevant documentation about the R27's guidance, I have seen some of it however it's in Russian and I haven't had the time to go through the arduous process of translating it.  But from what I could understand what has been said about the missile only using raw PN inside of 25km is correct.  We are also rather confident about the AIM-7 series using APN and the amraam/54C using optimal control as well.

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Cmptohocah

Cmptohocah

Posted
Posted (edited)
On 8/10/2022 at 5:47 PM, tavarish palkovnik said:

New output based on this assumed geometry and other inputs also assumed, unfortunately still everything is in assumptions, however taking consideration about common practice and theory, some basic rules and following “fingerprints” 

31764438-B28D-4930-B7CD-DB9EEABC583F.jpeg

mg=141kg

ro=1,78kg/dm^3

Iud=250s (pk:pa=40:1)

u=3,5*p^0,25 (p-bar)

Dkr=65mm

Nozzle throat erosion 0,5mm/s

Motor efficiency 95%

pa=0,1 MPa (full expansion to atmospheric pressure)

 

Must ask, is anyone of you guys good in 3D modeling? Solid Works and similar programs, and interested in this topic. This what I do in two dimensions adding third mathematically is painful, horrible and takes a while. Plus to all integration step is quite rough what makes output to be rough as well.

I would really like if someone knows modeling, has interest in this and has some free time so that we go thru this together. It will not be very demanding neither will take lot of time. Burning surface with offset for calculated burning rate, offset of new surface for new integrated rate etc etc

 

I could do the modeling, provided you can offer me detailed drawings on which I can model it.

Edited by Cmptohocah
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Cmptohocah=CMPTOHOCAH 😉

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