R-27ER Experiment & Findings

[IASGATG]

The real question is does the ISP/thrust look realistic. That's your homework assignment. X

[JunMcKill]

The first part is clear - the R-27R has a single-stage boost engine with 6 sec burn time, while the AIM-7M has a two-stage boost-sustain engine with 3.26 and 10.86 sec burn time respectively.

 

But what does those thrust and flow rate figures mean? - the boost thrust is much higher than in sustain stage, so why is there only one figure for the AIM-7...is it some sort of "accumulated engine power"?

 

Ah sorry, as IASGATG noted, the next line is the thrust in each stage, should be measured in newtons (N)

 

this is the AIM-7M with the two stages

-- t_statr t_b t_accel t_march t_inertial t_break t_end

 

0.0, 0.0 , 30645.0, 5194.0, 0.0, 0.0, 0.0, -- thrust

 

and this is the R-27R with only one stage

 

0.0, 0.0 , 25620.0, 0.0 , 0.0, 0.0, 0.0, -- thrust 6000 by doc

 

If you want to convert the newtons to Kg-force use this:

 

http://www.convertunits.com/from/newtons/to/kilogram-force

Edited April 5, 2017 by JunMcKill

[OnlyforDCS]

All of these missiles make me sad. The R-27R is so slow compared to what it should be, the 7M and 27ER hide it a little with the long burn times but it's still really depressing.

 

Makes me wonder how the different missiles would perform in these tests with your mod enabled. Especially the R, ER, and AIM7M which seem to deploy a brake chute as soon as they end their burn. :lol:

[GGTharos]

They don't perform that different unless in a straight-shot scenario. You do get more range out of them (a lot more in a straight shot), but they still do a lot of stuff to burn their energy off vs a maneuvering target.

 

We can even get those missiles to turn harder ... still at a cost to energy :)

[Seaeagle]

The real question is does the ISP/thrust look realistic. That's your homework assignment. X

 

Heh I couldn't tell, but I think it looks strange. If I understand the numbers correctly, the AIM-7 has a higher output in boost stage(but for a shorter period) than the R-27R although it has a smaller body diameter.

 

With the R-27R having a larger motor section and only a 6 sec burn time, I would have expected it to be the other way around - certainly not less.

[Seaeagle]

Ah sorry, as IASGATG noted, the next line is the thrust in each stage, should be measured in newtons (N)

 

this is the AIM-7M with the two stages

-- t_statr t_b t_accel t_march t_inertial t_break t_end

 

0.0, 0.0 , 30645.0, 5194.0, 0.0, 0.0, 0.0, -- thrust

 

and this is the R-27R with only one stage

 

0.0, 0.0 , 25620.0, 0.0 , 0.0, 0.0, 0.0, -- thrust 6000 by doc

 

If you want to convert the newtons to Kg-force use this:

 

http://www.convertunits.com/from/newtons/to/kilogram-force

 

Thanks - yes I understand now. It was the single thrust figure for the AIM-7 and that it was higher than for the R-27R that baffled me - and as mentioned above the latter still does :) .

[esb77]

Nozzle design has a pretty big effect on ISP and thrust for rockets, that might be it.

 

 

If I were going to guess I'd wonder if maybe the AIM - 7 and AIM 120 have more optimized convergent-divergent nozzles while the R-27 family has easier to manufacture convergent- divergent nozzles.

 

I have no actual information on this, just speculation based on Soviet and US design philosophies.

[GGTharos]

The more you look at the numbers the more you will be baffled.

 

There's no guarantee that numbers aren't adjusted (Actually, you're almost guaranteed that they are :) ) to achieve a realistic speed-time graph for the missile, which is what matters for the missile's performance.

 

The by-the-book thrust value of the AIM-7 rocket motor should be 22500-25500N/m. I don't recall the exact number. Likewise for the sustain stage it should be closer to 4500.

[Seaeagle]

I don't know either, but would nozzle design also affect the "flow rate"? - I am reading this as the rate at which the fuel is burned, so wouldn't it more likely be down to the type of propellant used for boost?

 

Then again if the R-27R has a bigger engine and burns off all its propellant in just 6 seconds(all boost), then how can the flow rate be lower?

[Seaeagle]

The more you look at the numbers the more you will be baffled.

 

There's no guarantee that numbers aren't adjusted (Actually, you're almost guaranteed that they are :) ) to achieve a realistic speed-time graph for the missile, which is what matters for the missile's performance.

 

The by-the-book thrust value of the AIM-7 rocket motor should be 22500-25500N/m. I don't recall the exact number. Likewise for the sustain stage it should be closer to 4500.

 

Ok thanks :) .

[Drona]

With R-27 series missiles being so ineffective at any range, its just not fun/satisfying anymore to fly the Su-27/Su-33 & MiG-29s in any BVR fight because the missiles just don't work. The only weapon that is useful on the Flankers and Fulcrums right now is the Gsh-301 cannon!

[ked]

With R-27 series missiles being so ineffective at any range, its just not fun/satisfying anymore to fly the Su-27/Su-33 & MiG-29s in any BVR fight because the missiles just don't work. The only weapon that is useful on the Flankers and Fulcrums right now is the Gsh-301 cannon!

 

I agree, everytime i try doing BVR the fight ends in close range combat and i've got to finish the ennemi with R73s ... Something's wrong tbh

[*Rage*]

4 years now we've been talking about how broken the ER/R guidance is...

[Ironhand]

With R-27 series missiles being so ineffective at any range, its just not fun/satisfying anymore to fly the Su-27/Su-33 & MiG-29s in any BVR fight because the missiles just don't work. The only weapon that is useful on the Flankers and Fulcrums right now is the Gsh-301 cannon!

Against the AI the R-series are reasonably effective, once you are about half way between Rmax and Rtr. It's in the online arena that the issues occur. Human's fly much more "erratically" and use far more countermeasures.

[IASGATG]

I take back what I said about the thrust/ISP's, they all like up okay. I'm not sure if something got changed at some point but I have a memory of the 27 or the 7M having a thrust value which would have given an ISP of around 700 (2.5times greater than what the fuel can give at 100% efficiency).

 

Rage, buddy, doesn't the videos continue to show how this isn't just guidance issue? Even for zero chaff encounters..

 

Against the AI the R-series are reasonably effective, once you are about half way between Rmax and Rtr. It's in the online arena that the issues occur. Human's fly much more "erratically" and use far more countermeasures.

 

Doesn't this mean that they aren't effective then? That even against dumb AI the missile in a high pK parameter it performs "reasonably".

[GGTharos]

Actually, if you consider that the Rmax parameter in RL for the R-27 is at 0.7pk (it's the only figure we have) and combat Pk for sparrow in reality was 0.34 when it was last used, it seems pretty close for the AI if I recall the numbers that Ironhand mentioned correctly.

Edited April 6, 2017 by GGTharos

[esb77]

I agree, everytime i try doing BVR the fight ends in close range combat and i've got to finish the ennemi with R73s ... Something's wrong tbh

 

I could have sworn that I read somewhere that Soviet design philosophy for the Su-27 was based on the notion that the majority of air combat scenarios would be resolved in the WVR arena.

 

That being the reason that they had IRST and high off bore helmet cueing systems as standard features long before the US did.

[Ironhand]

...

 

Doesn't this mean that they aren't effective then? That even against dumb AI the missile in a high pK parameter it performs "reasonably".

Sigh... there must be an easier way... I'm trying to post using an ipod and it's not cooperating. Wrote my reply, pushed send and only the quote appeared. So trying again.

 

I used the modifier "reasonably" because it's not 100% true and I don't feel like taking time to track this stuff and quantify it. But...most of my BVR duels with the AI stay BVR. Either the 2nd or 3rd missile makes the kill. The first is an Rmax throw away. (It's a bad habit I've developed.)

 

My point is actually that the same missile coding may not work in both the SP and MP environments. One, the other, or both will suffer.

Edited April 6, 2017 by Ironhand

[GGTharos]

Then why did they try to compete with BVR equipment?

 

The real answer IMHO is that they knew their BVR equipment was inferior, and they simply had no other choice but to resolve air combat in the BVR arena. They would thus tailor their tactics and engagements to attempt and deny the other guy's advantage and press their own.

 

The reason they had IRST is because they wanted something that would work when their radars get jammed.

 

I could have sworn that I read somewhere that Soviet design philosophy for the Su-27 was based on the notion that the majority of air combat scenarios would be resolved in the WVR arena.

 

That being the reason that they had IRST and high off bore helmet cueing systems as standard features long before the US did.

[GGTharos]

Exactly correct. The only way to make all of this work correctly is a huge under-taking because it involves, IMHO:

 

1) Adding more logic/algorithms for countermeasure characterization than probability of decoy by CM (modified by look down/up, sun in the way, number of CMs in view) and implementing the notion of centroids generated by these CMs for sensors that have low enough resolution to affected in this way (Every heater up to FPA based heaters, vast majority of radar seekers).

 

This will significantly differentiate flares and chaff at minimum, and add infrastructure to differenciate generations of missiles and how they handle CMs. By adding basic, more realistic ECCMs algorithms as well, you will now have to combine CM + maneuver to evade, but at the same time you'll find that some types of missiles (heaters especially) are much easier to decoy, even in AB. If you consider radar guided stuff, it's more resilient (more available data to deal with decoys) but you get into trouble once you add ECM, assuming that would happen.

 

2) The AI will have to learn how to evade using decoy+maneuver. Just basics, but it's not easy when you go beyond simple statistics for decoying the missiles.

 

The bottom line is that IMHO don't expect anything to change without a code re-write, and even then there will absolutely be differences between MP/SP, due to the fact that MP is flat out laggy compared to SP. It can be mitigated but now there's even more work to do with respect to fuzes and fragmentation effects for example.

 

 

 

My point is actually that the same missile coding may not work in both the SP and MP environments. One, the other, or both will suffer.

[karambiatos]

For now a great stop gap measure would be to reduce the dice roll chances of missiles getting decoyed. So that us players can have something until the realistic stuff is implemented. Or rather if it is implemented.

[GGTharos]

I consider it 'a' stop gap, not 'a great' stop gap for two reasons:

 

1) It (maybe slowly but surely) reduces differentiation between missiles to nothing more than their rocket motors.

2) The real deal knew their BVR equipment was not as good as the other guy's, so they devised tactics and hoped they could use them to push the fight into WVR.

 

Oh noes, now I'm hinting at guidance!

[karambiatos]

They knew their stuff want as good. But what we have in dcs currently would have gotten you fired. And im talking here about both sides not these guys and those guys or those ones over yonder

 

As for point 1. Today the difference is the same only instead of sarhs hitting anything they dont. Which brings as to point 2. Id call the aim7 only marginally better than then the r27.

Edited April 6, 2017 by karambiatos

[GGTharos]

I don't know, I got pretty salty after taking a SARH in the side the other day. I mean it doesn't get more comical, it was like 'But they keep saying these don't hit anything!'

[karambiatos]

Yeah im not saying they dont hit but them hitting is an exception rather then a rule. What was it? Less than 30 percent of the time against a non maneuvaring target thats chaffing? From ironhands tests

Edited April 6, 2017 by karambiatos