Ракеты в DCS

[Hoarfrost]

3 часа назад, Chizh сказал:

Скажем в районе 10%. В любом случае если мы применим коэффициенты рассчитанные через CFD ракета будет летать немного медленнее и ближе.

Я ожидал что после продувок будет наоборот +10, а здесь -10)))

Но что то не то, не дотягивала она до номограммы, как раз 10. 

[BlackPixxel]

4 hours ago, Chizh said:

Скажем в районе 10%. В любом случае если мы применим коэффициенты рассчитанные через CFD ракета будет летать немного медленнее и ближе.

 

Does this already consider the reduced drag in the rear of the missile as long as the motor is burning?

With a burntime of 10 seconds, this reduction in drag could have a significant impact

 

Regarding the boost/sustain ratio:

Is the current 3s/7s based on sources, or an educated guess?

Edited April 3, 2021 by BlackPixxel

[Max1mus]

Why is the R-27R getting a 10-20% of additional range then? Shouldnt both the ER and 27R be nerfed then? For the current R-27R this would mean less range than R-73, but if your research shows this @Chizh ...

Edited April 3, 2021 by Max1mus

[Chizh]

32 minutes ago, Hoarfrost said:

Но что то не то, не дотягивала она до номограммы, как раз 10. 

Р-27ЭР давно дотягивает до номограммы.

[dundun92]

54 minutes ago, Max1mus said:

This seems like some 10 year old trick ED used to control maximum speed of missiles.

This is simply just boost sustain motors doing their thing. The whole point is to hit a top/optimal speed quickly, and then hold it/slowly accelerate, or in the say AIM-7s case slowly loose speed when at lower altitudes. Test it at higher altitudes and in the sustain phase it will gain speed.

  

54 minutes ago, Max1mus said:

Compare this to the AMRAAM or AIM-7

AIM-120C uses all boost, AIM-120B is boost sustain, but with a bigger boost rather than bigger sustain edit, not bigger boost, but the sustain is much more powerful in terms of thrust to drag/weight compared to the sustain on say the ER. AIM-7, a boost sustain with more sustain, but a higher percentage of boost than sustain compared to the ER (4.5/11s for AIM-7 as a reference).

 

Heres a TAS vs time for a 40kft M1.5 shot profile to illustrate:

Edited April 3, 2021 by dundun92

[Chizh]

59 minutes ago, BlackPixxel said:

 

Does this already consider the reduced drag in the rear of the missile as long as the motor is burning?

With a burntime of 10 seconds, this reduction in drag could have a significant impact

We does not consider the body base drag regardless motor burning.

 

Quote

Regarding the boost/sustain ratio:

Is the current 3s/7s based on sources, or an educated guess?

The engine burning time is known from documents and ranges from 6 to 11 seconds depending of the temperature.

Also known that buster mode works about 3 sec.

[BlackPixxel]

1 minute ago, Chizh said:

We does not consider the body base drag regardless motor burning.

 

The engine running time is known from documents and ranges from 6 to 11 seconds depending on the temperature.

 

What do you mean with the body base drag? The effect of the rear of the missile on the deceleration is always ignored, not just when the motor is burning?

 

I did not mean the total burntime, but how it is split up into boost and sustain. Right now it is 3 s boost and 7 s sustain. Are those values from documentation or guesses?

[GGTharos]

 

1 hour ago, Max1mus said:

It would still be better than now. The ER does not benefit from this 7-8 second sustain motor at all, it gains practically no new speed...

 

There's a reason why it's called a sustain motor, it's job is to sustain the speed.  Look at the AIM-7, the sustain motor is so weak that until above a certain altitude, it's losing speed.

 

Quote

Compare this to the AMRAAM or AIM-7 - it keeps happily accelerating to mach 4-5.

 

Where have you seen an AIM-7 accelerate to M5?  The 7 can attain M4 but you have to shoot from M2.

 

Quote

This seems like some 10 year old trick ED used to control maximum speed of missiles. If i remember right, the old AIM-120 would behave like this too, hitting a top speed and keeping it until the motor burned out.

 

In the (really old) FM that was a thing, but it's not a thing in the (old) FM as in the one just before the current advanced one.   There's a drag force that depends on the drag coefficients and speed SQUARED.   The draggier the missile, the bigger the coefficients and thus the force.  The R-27 is quite draggy compared to a 120.

7 minutes ago, BlackPixxel said:

 

What do you mean with the body base drag? The effect of the rear of the missile on the deceleration is always ignored, not just when the motor is burning?

 

I did not mean the total burntime, but how it is split up into boost and sustain. Right now it is 3 s boost and 7 s sustain. Are those values from documentation or guesses?

 

Ignored or not ignored, same thing, same result.  If they include it in the calculations it you get shorter range, if not you get longer range.

Edited April 3, 2021 by GGTharos

[Chizh]

10 minutes ago, BlackPixxel said:

 

What do you mean with the body base drag? The effect of the rear of the missile on the deceleration is always ignored, not just when the motor is burning?

Yes. Ignored in the current implementation.

 

10 minutes ago, BlackPixxel said:

 

I did not mean the total burntime, but how it is split up into boost and sustain. Right now it is 3 s boost and 7 s sustain. Are those values from documentation or guesses?

Current times are 2.5 + 6.5 seconds. The ratio is taken from the docs.

[BlackPixxel]

30 minutes ago, Chizh said:

Yes. Ignored in the current implementation.

 

Current times are 2.5 + 6.5 seconds. The ratio is taken from the docs.

 

In DCS it is 3 + 7 seconds. Will it be changed to 2.5 + 6.5? Also, 9 seconds total instead of 10?

Edited April 3, 2021 by BlackPixxel

[Max1mus]

2 hours ago, dundun92 said:

AIM-120C uses all boost, AIM-120B is boost sustain, but with a bigger boost rather than bigger sustain edit, not bigger boost, but the sustain is much more powerful in terms of thrust to drag/weight compared to the sustain on say the ER. AIM-7, a boost sustain with more sustain, but a higher percentage of boost than sustain compared to the ER (4.5/11s for AIM-7 as a reference).

 

AIM120B_sustain.trk AIM-120B happily accelerates at very high rate (i dont even think lower than the initial boost rate) despite "sustain" boost. Why not R-27ER?

If the R-27ER rocket motor was modelled even remotely like AIM-120B one here, where it does not just hit a stopgap after 3 seconds, we would see way different results.

2 hours ago, Max1mus said:

Why is the R-27R getting a 10-20% of additional range then? Shouldnt both the ER and 27R be nerfed then? For the current R-27R this would mean less range than R-73, but if your research shows this @Chizh ...

 

I assume R-27R/T is not getting the 10-20% range increase this update, or is even getting a 10% decrease. Anything else would be a double standard, since the missile bodies of 27R/27ER are very similar.

Edited April 3, 2021 by Max1mus

[nighthawk2174]

8 hours ago, FoxAlfa said:

Yeah, true, ISP are off but the stage weights also seam arbitrary slaped on.

 

I did come across 2-8 sec split instead of 3-7 on other misslie forums and sources too.

 

Some of them were talking about new 2014 version with 9000kg stage instead of 7500kg... I didn't find the claim credible enough to share...

 

All in all 2-8 gives higher end speed at longer range but it takes longer to get there so I am not sure what is better.

 

If you were supposed to use R-27R at closer range I would go for that configuration, if the R-27ER was supposed to replace the R-27R I would go for 3-7... 

 

 

 

Really the only solid data we have on what it looks like for a boost-sustain motor comes from the AIM-7F SMC doc where we get ~23470N for boost and ~4530N for sustain or a 5.2/1 ratio.  Burn time is 4.5/11 or .41/1 ratio.  And fuel wise its 37.65/23.6kg or 1.6/1 ratio.  Currently the ER is 5/1 thrust ratio, .43/1 for burn time, and 2.16/1 for each of these ratios respectively which imo seems quite reasonable. Based on a known boost/sustain motor.  The current AMRAAM is quite off from this which is why I have doubts about its motor stats but well imho the current ER is reasonable here and is unlikely to be the cause of performance discrepancies.

 

Действительно, единственные достоверные данные о том, как он выглядит для двигателя boost-sustain, получены из документа AIM-7F SMC doc, где мы получаем ~23470N для boost и ~4530N для sustain или соотношение 5,2/1. Время горения составляет 4,5/11 или 0,41/1. И топливо мудрое его соотношение 37,65/23,6 кг или 1,6/1. В настоящее время ER составляет 5/1 отношение тяги, .43/1 для времени горения и 2.16/1 для каждого из этих соотношений соответственно, что имо кажется вполне разумным. На основе известного двигателя наддува/сустейна. Текущий AMRAAM довольно далек от этого, поэтому у меня есть сомнения относительно его моторных характеристик, но хорошо имхо, что текущий ER здесь разумен и вряд ли будет причиной расхождений в производительности.

Edited April 3, 2021 by nighthawk2174

[dundun92]

32 minutes ago, Max1mus said:

AIM-120B happily accelerates at very high rate (i dont even think lower than the initial boost rate) despite "sustain" boost. Why not R-27ER?

If the R-27ER rocket motor was modelled even remotely like AIM-120B one here, where it does not just hit a stopgap after 3 seconds, we would say way different results.

Because the AIM-120B sustain is set up differently than the ER sustain. The AIM-120B sustain is a much higher thrust/weight than the ER sustain. Thats just how the motors are designed, you can take up your complaint with Vympel and Raytheon if you want .

To give the numbers, the ER has a 73kN boost for 3 sec, and 14.5kN sustain for 7 sec. The 120B has 20kN boost for 2.1 sec, and 12kN sustain for 5 sec. You can immediately see the difference here. The 120B, a lighter missile has a sustain with almost the same thrust as the much heavier ER. In addition, the 120B sustain has about 60% of the thrust of the boost; the ER sustain thrust is 20% of the boost thrust, which is why the ER has a much more distinct sustain transition. So yes, the AIM-120B sustain is more like a boost-smaller boost, where the ER is more of a true boost-sustain.

Edited April 3, 2021 by dundun92

[Max1mus]

1 minute ago, dundun92 said:

Because the AIM-120B sustain is set up differently than the ER sustain. The AIM-120B sustain is a much higher thrust/weight than the ER sustain. Thats just how the motors are designed, you can take up your complaint with Vympel and Raytheon if you want .

To give the numbers, the ER has a 73kN boost for 3 sec, and 14.5kN sustain. The 120B has 20kN boost for 2.1 sec, and 12kN sustain for 5 sec. You can immediately see the difference here. The 120B, a lighter missile has a sustain with almost the same thrust as the much heavier ER. In addition, the 120B sustain has about 60% of the thrust of the boost; the ER sustain thrust is 20% of the boost thrust. So yes, the AIM-120B sustain is more like a boost-smaller boost, where the ER is more of a true boost-sustain.

First of all, i think the 120B in DCS does not have these 2 stages modelled. I see no difference in acceleration between the first 2.1s and the last 5s.

Secondly, the ERs 73kN boost may then just be too weak in DCS. How many kN does the AIM-120C motor have in total? Because just these initial 73kN are much more than that, and that difference just is not showing. On the AIM-54 on the other hand, it is, and that one is really just an extreme version of the R-27ER.

120C_ER_Difference.trk Just look at this. The AIM-120 almost outspeeds the ER (only ~M 0.1-0.15 slower).

And this is under the best conditions.
- on the deck (where missiles with the biggest motors benefit most compared to gliders like AIM-120)
- with no maneuvering (where lower AIM-120 lift drag and better AIM-120 guidance help it)
- Fast target assumed (i stop the track when missiles are under mach 1.36), AIM-120 glides forever at slower speeds.

120C_bigER_difference.trk Look at the difference between the phoenix and 120C under the same conditions. Here, the differences between the 2 rocket motors are clearly visible in both top speed and flyout range. Of course, as mentioned, this difference gets smaller at high altitude (though even with the MK47 variant, it never disappears completely) due to the AIM-120s better aerodynamics AFTER the booster runs out.

[HWasp]

Current R-27R top speed at 1000m is around 820 m/s launched at 1150 km/h

Current R-27ER top speed at 1000m is aroud 1020 m/s launched at 1150 km/h (at 3 second after launch) and 950 m/s when fuel is depleted.

 

R-27R deceleration between 770 and 720 m/s is 74,9 m/s2 average

R-27ER decel.          between same speeds is 53,1 m/s2 average

 

Empty 27R is 185 kg and empty 27ER is 210 kg

 

So 27R has 40% more deceleration while only about 12% lighter and aerodynamically better ---- > R-27R drag can be improved a lot, it has a lot more drag than the 27ER

[BlackPixxel]

7 minutes ago, Max1mus said:

Secondly, the ERs 73kN boost may then just be too weak in DCS. How many kN does the AIM-120C motor have in total? Because just these initial 73kN are much more than that, and that difference just is not showing. On the AIM-54 on the other hand, it is, and that one is really just an extreme version of the R-27ER.

 

The boost of the ER is based on real documents (7500 Kg according to a MiG-29 manual)

[dundun92]

49 minutes ago, Max1mus said:

does not have these 2 stages modelled.

It does. Its in the files and you can verify this in game, this isnt gonna be some huge difference here because the missile is also loosing mass fast. But its noticeable.

 

49 minutes ago, Max1mus said:

How many kN does the AIM-120C motor have in total?

18kN

49 minutes ago, Max1mus said:

Because just these initial 73kN are much more than that, and that difference just is not showing.

Because the ER is heavier. What you need to do is calculate Delta V to see the max change of velocity possible. I have not done this for the ER (i will dot it and update the post), but for the 120C its 876 m/s.

Edited April 3, 2021 by dundun92

[Max1mus]

45 minutes ago, BlackPixxel said:

 

The boost of the ER is based on real documents (7500 Kg according to a MiG-29 manual)

Depends how its implemented in DCS. The tiny difference in top speed (and low altitude flyout) between AIM-120 and R-27ER is weird, given the insanely higher amount of fuel in the R-27.

11 minutes ago, dundun92 said:

 

Because the ER is heavier. What you need to do is calculate Delta V to see the max change of velocity possible. I have not done this for the ER, but for the 120C its 876 m/s.

 

How many total kN does the AIM-54 have? Both MK47 and MK60. They are even more heavy, yet achieve 3-4x as much flyout on the deck as AIM-120. R-27ER barely even exceeds it, despite being lighter.

Edited April 3, 2021 by Max1mus

[dundun92]

12 minutes ago, Max1mus said:

How many total kN does the AIM-54 have? Both MK47 and MK60.

Mk47 is 16kN, Mk60 is 18kN

FYI, im pulling these straight from the .lua (missiles_data for ER, missiles_table for the 120 (note that math had to be done as the 120s thrust isnt directly stated, just the mass flow and ISP), and AIM-54 was from C:\Program Files\Eagle Dynamics\DCS World OpenBeta\CoreMods\aircraft\F14\Entry\Weapons.lua)

Edited April 3, 2021 by dundun92

[dundun92]

12 minutes ago, Max1mus said:

They are even more heavy, yet achieve 3-4x as much flyout on the deck as AIM-120. R-27ER barely even exceeds it, despite being lighter.

because max speed has to do with do with the delta V or max change in velocity. The delta V equation is Ve*ln(mf/me), Ve is effective exhaust velocity in m/s, which is either specific impulse (ISP) times sea level gravity (9.80665 m/s^2), or thrust/mass flow rate. Mf is mass at start of of burn, me is empty mass. I did calculate it for the AIM-54s; i dont remember the exact value but it was >1000 m/s/

[Max1mus]

39 minutes ago, dundun92 said:

Mk47 is 16kN, Mk60 is 18kN

FYI, im pulling these straight from the .lua (missiles_data for ER, missiles_table for the 120 (note that math had to be done as the 120s thrust isnt directly stated, just the mass flow and ISP), and AIM-54 was from C:\Program Files\Eagle Dynamics\DCS World OpenBeta\CoreMods\aircraft\F14\Entry\Weapons.lua)

 

Make sure you get the info for the heatblur AIM-54.

 

These values are just for code then and not 1:1 translations from IRL. The AIM-54 surely has more acceleration than an ER.

[dundun92]

1 hour ago, Max1mus said:

Make sure you get the info for the heatblur AIM-54.

 

These values are just for code then and not 1:1 translations from IRL. The AIM-54 surely has more acceleration than an ER

Yes, I did get the HB F-14 values. And no, the AIM-54 really has that little thrust IRL.

[GGTharos]

1 hour ago, Max1mus said:

Make sure you get the info for the heatblur AIM-54.

 

These values are just for code then and not 1:1 translations from IRL. The AIM-54 surely has more acceleration than an ER.

 

It does not.  It has about 4g of thrust at launch and stays at that thrust.  In exchange it burns for nearly half a minute instead of 10 seconds.

3 hours ago, nighthawk2174 said:

Really the only solid data we have on what it looks like for a boost-sustain motor comes from the AIM-7F SMC doc where we get ~23470N for boost and ~4530N for sustain or a 5.2/1 ratio.  Burn time is 4.5/11 or .41/1 ratio.  And fuel wise its 37.65/23.6kg or 1.6/1 ratio. 

 

3.5/11, the 4 is a typo in the SMC as are the weights for the different thrust stages:  They are reversed.  So in case anyone wonders how 'official documents can be wrong', there you go.

[Max1mus]

On 4/2/2021 at 1:49 PM, BlackPixxel said:

 

 

 

According to this drawing, R-27ER should have 13km+ of flyoff at 1000m of altitude. So if drag is the same, then clearly something is horribly wrong with the rocket motor in DCS. In DCS, you get 9-10km.

Edited April 4, 2021 by Max1mus

[GGTharos]

According to what exactly?   The red line at 1km reads maybe 10km, not even.