How does the SD-10 missile compare to the AIM-120C?

[LJQCN101]

I think we did address the Cx0 issue to ED directly and if you were right, the missile will be tuned. Let's see how it goes.

[Exorcet]

AMRAAM's PN constants might need a little more tuning but they effectively behave the same way. The difference is that AMRAAM gets slow a lot faster - it's much too draggy in game. SD-10 on the other hand doesn't have enough drag.

The AMRAAM also still kills its speed when it comes out of a loft. At 50000 ft it should probably be close to the SD-10 at 30000 ft, but in the video posted it was much slower, I'm pretty sure the loft it uses it responsible for that at least partially.

[GGTharos]

The loft needs to be addressed separately and I'm actually quite certain that ED is on it.

[DA_FLY]

Blue guys finally get a taste of what we have been going through every day in an MP server. Enjoy the experience

[WingC3]

Appreciation

 

I think we did address the Cx0 issue to ED directly and if you were right, the missile will be tuned. Let's see how it goes.

 

Your openness to feedback is really commendable. I think the majority of the tuning needs to be to the 120 and other FC3-era missiles, but continuing to ensure the accuracy of your models too is appreciated. :)

[Exorcet]

Your openness to feedback is really commendable. I think the majority of the tuning needs to be to the 120 and other FC3-era missiles, but continuing to ensure the accuracy of your models too is appreciated. :)

I'm leaning this way as well, the SD-10 in practice doesn't seem unreasonable. If it is overtuned, I feel like it's closer to an actual missile than the current AIM-120. Some kind of CFD analysis is the only way to really know though.

 

 

Also a question for the devs, are there any plans to make the SD-10 available for the J-11, or is it only the J-11B that can carry it? It would be nice to have those fighters equipped with a longer range missile while waiting for the R-77 overhaul.

[WingC3]

I'm leaning this way as well, the SD-10 in practice doesn't seem unreasonable. If it is overtuned, I feel like it's closer to an actual missile than the current AIM-120. Some kind of CFD analysis is the only way to really know though.

 

 

Also a question for the devs, are there any plans to make the SD-10 available for the J-11, or is it only the J-11B that can carry it? It would be nice to have those fighters equipped with a longer range missile while waiting for the R-77 overhaul.

 

 

That would be interesting indeed. Since the R-77 suffers from the same auto-deploying drag chute the moment its motor is expended.

[AeriaGloria]

Only J-11B

[Mars Exulte]

The butthurt in this thread pleases me.

[CoBlue]

The SD-10 is OP, how can it have such out of this world performance?

[Terrorban]

And yet this is the closest thing we have to a realistic missile behaviour and range when compared with AIM-120. Hard to believe, I know.

[Exorcet]

The SD-10 is OP, how can it have such out of this world performance?

I think the problem in that video is the F-15 reversing direction. It works against other missiles because they slow down faster and have to use more lead to track their targets. Dragging the SD-10 into a higher and higher AoA turn seems to work.

SD-10_combat_F-15_defeated.trk

SD-10_combat_F-15_defeated_2.trk

[Sn8ke_iis]

Somebody help me out here. How are we defining "accurate" and "realistic" in this context?

 

I see how we can get a reasonable approximation of D and Cd from a photograph because we can see A.

 

https://www.grc.nasa.gov/WWW/k-12/airplane/dragco.html

 

https://www.grc.nasa.gov/WWW/k-12/airplane/drageq.html

 

Where are we getting all the other variables and parameters? e.g. thrust, burn time, weight?

 

I keep seeing phrases like "OP", "I feel", "based on the information available", "behaving like I would expect". I don't get it.

[Kula66]

Knowing almost nothing of the technical details: How about volume of propellant? Isn't it an 8" diameter missile compared to AMRAAMs 7" diameter, so assuming the propellant has similar 'thrust/lb', therefore the SD has x times (you can work it out) more? You may also be able to work out the length of the motor section from external photos ... too simplistic I know, but at least a base on something tangible!

[MrDieing]

I keep seeing phrases like "OP", "I feel", "based on the information available", "behaving like I would expect". I don't get it.

 

It's called being an internet engineer. Everybody is a professional on the subject because they have valid sources like Wikipedia. Unfortunately you will see a whole lot of these phrases when it comes to missile dynamics and flight models.

[Sn8ke_iis]

It's called being an internet engineer. Everybody is a professional on the subject because they have valid sources like Wikipedia. Unfortunately you will see a whole lot of these phrases when it comes to missile dynamics and flight models.

 

DING, DING, DING, DING, DING, DING...We have a winner!!!

 

I'm definitely not an engineer but I did have math classes with them at my University. I'm pretty sure they didn't pass those classes with their subjective feelings.

Edited December 8, 2019 by Sn8ke_iis

[Terrorban]

Let’s not forget that developers have a whole team working on these weapons and features so when one person comes here throwing big paragraphs around on how something is wrong, they are claiming that they have more knowledge than the team who developed it.

[falcon_120]

Let’s not forget that developers have a whole team working on these weapons and features so when one person comes here throwing big paragraphs around on how something is wrong, they are claiming that they have more knowledge than the team who developed it.

Well to be honest we've also had already 3rd party developers who have introduced stupidly broken and not well researched weapons, and a certain helicopter flight model that is not at the same standards of every other chopper in DCS (mistral/gazelle to be more specific). Not saying at all this is the case with Deka, to be clear, but we cannot deny that this is a problem/risk that needs to be considered in DCS. They dont have to do it on purpose, it could be just a case of different interpretations of the same values or a different engineering approach to a problem which works or behave different within the dcs engine. Thats why design principles and standards exist in our daily lives for all types of knowledge areas.

 

Enviado desde mi SM-G950F mediante Tapatalk

Edited December 8, 2019 by falcon_120

[Terrorban]

Well to be honest we've also had already 3rd party developers who have introduced stupidly broken and not well researched weapons, and a certain helicopter flight model that is not at the same standards of every other chopper in DCS (mistral/gazelle to be more specific). Not saying at all this is the case with Deka, to be clear, but we cannot deny that this is a problem/risk that needs to be considered in DCS. They dont have to do it on purpose, it could be just a case of different interpretations of the same values or a different engineering approach to a problem which works or behave different within the dcs engine. Thats why design principles and standards exist in our daily lives for all types of knowledge areas.

 

Enviado desde mi SM-G950F mediante Tapatalk

 

I completely agree with you there. However you do have to look at the capabilities of the developer in this regard. The features provided in this jet are on par with F/A-18. There is another certain developer who attempted to do a modern jet (which can hover) and we all know how that development is going. Their fans (including me) will just be happy to get the features implemented rather than complain about their realistic accuracy. The main thing which is bringing people to this thread is because they want multiplayer balance so when they get taken down by a JF-17, they quickly come here to vent their anger. Deep down they fear that ED will not fix the AIM-120 anytime soon so they are attempting to get this missile’s performance reduced.

 

That said, I also appreciate the attempts of people who can provide reasonable data to back their claim than just calling the missile out of this world tech.

[QuiGon]

What I'm going to say now is only half-science, because I haven't run enough tests at this point:

 

 

You have a very (un-physically) low Cx0 at high mach (I have the DCS dragbuilder and I've just ran the numbers to produce the DCS Cx0 graph).

Nothing has such low drag at this size - it's about 1/3 of the drag of any other low-drag missile that I've seen a CFD or empirical study for.

The fact is that this drag is probably too low in the subsonic region also.

 

This results in the missile keeping a lot of speed for much longer than it should.

A lot of speed means little maneuvering vs. a target, since the intercept point at all times remains near the target (of course, this only really matters when PN constant is relatively high, so within 5km in this case).

 

I have not analyzed Cy0 as that is much more difficult and my understanding of it is a lot more superficial, but at the same time - Cy0 and Cx0 combine to produce loaded drag - ie. drag under AoA. With such low Cx0, the missile isn't paying the price for making turns, not that it ever seems to make high-g turns.

 

 

The CFD curve for AMRAAM in DCS looks like this:

 

 

0.023

0.048

0.40

0.027

2.3

1.5

 

 

Your numbers look like this:

 

 

0.012

0.042

0.012

0.003

1.20

1.50

 

They shouldn't be THAT different, since these are drag coefficients.

 

Finally, your rocket motor has a 6sec boost and 4sec sustain. This is not impossible of course, but it is unusual - for a boost-sustain motor I'd expect the opposite configuration. Boost-sustain AAMs most tend to be slower than all-boost variants, but at the same time there are exceptions for missiles with exceptionally powerful sustainers (eg. R-27E, and you might say AIM-54 is all-sustain).

In this, the SD-10 squarely falls between AMRAAM and AIM-7 in total weight. I don't know what the fuel fraction is supposed to be - maybe it is unusually high but if not then I expect it to have behavior between AIM-7 and AMRAAM and right now it exceeds them by a lot and here I refer to IRL + CFD data.

 

 

 

We can talk about more accurate tuning because nothing is perfect, but the numbers you have a very uncharacteristically low which is why you get so much 'hang time' from this missile, and so much speed at ranges where it shouldn't be having them.

 

 

I would be expecting in the 70km Rmax scenario that this missile would hit with M1.2-1.3 maybe. Right now it carries a lot more speed.

Interesting stuff, thanks!

[GGTharos]

Somebody help me out here. How are we defining "accurate" and "realistic" in this context?

 

I see how we can get a reasonable approximation of D and Cd from a photograph because we can see A.

 

https://www.grc.nasa.gov/WWW/k-12/airplane/dragco.html

 

https://www.grc.nasa.gov/WWW/k-12/airplane/drageq.html

 

Where are we getting all the other variables and parameters? e.g. thrust, burn time, weight?

 

I keep seeing phrases like "OP", "I feel", "based on the information available", "behaving like I would expect". I don't get it.

 

 

You keep seeing 'I feel that its overtuned' and 'I feel it's more like a missile and it's the other missiles that are wrong' because people don't have a clue.

 

 

You can get a ball-park Cd or a more accurate Cd according to the technique you use, and there exist plenty of empirical drag measurements of missiles or missile-like bodies so that you can compare the overall shape of the Cd graph as well.

 

 

Ball-park Cd can be be built up by looking up a table of shapes in say, something like Fleeman's books. It's not super accurate but it can tell you if you're in the right place.

 

 

More accurate Cd can be either measured (we don't have one for SD-10) or computed via CFD (we have that the 120, IASGATG and friends took weeks to make it happen - IASGATG now works for an employer that is actually involved in this stuff for real so as of then he doesn't participate in such efforts).

 

 

And this is the ONLY comparison point that's in any way valid, is that CFD which just happens to be for the 120 and again this is ball-park comparable to an SD-10, but much closer ball-park than building up from a list of shapes - there's no need for comparison between in-game entities since this is inappropriate.

 

 

 

As for the shape of the graph itself - the SD-10 in-game has the same drag coefficients for subsonic and high supersonic mach numbers. But pretty much every missile out there has a higher supersonic drag than subsonic, at least up to the mach numbers we're concerned about.

 

 

We don't have enough information about the rocket motor configuration of the SD-10. We know it's boost-sustain, but the only equivalent rocket motor we have to compare it to is the AIM-7, for which we do have information.

The SD-10 is a much newer missile, and it may actually have a higher fuel fraction and other good things that will give it better performance than the AIM-7.

However, the boost-sustain stages are set up with a long boost and short sustain, which isn't how things are usually done and doesn't even make a lot of sense since all boost would get you to a higher peak speed and those extra 4 sustain seconds become irrelevant. Also makes the rocket easier to build with a single grain instead of dual grain.

[Terrorban]

You keep seeing 'I feel that its overtuned' and 'I feel it's more like a missile and it's the other missiles that are wrong' because people don't have a clue.

 

 

You can get a ball-park Cd or a more accurate Cd according to the technique you use, and there exist plenty of empirical drag measurements of missiles or missile-like bodies so that you can compare the overall shape of the Cd graph as well.

 

 

Ball-park Cd can be be built up by looking up a table of shapes in say, something like Fleeman's books. It's not super accurate but it can tell you if you're in the right place.

 

 

More accurate Cd can be either measured (we don't have one for SD-10) or computed via CFD (we have that the 120, IASGATG and friends took weeks to make it happen - IASGATG now works for an employer that is actually involved in this stuff for real so as of then he doesn't participate in such efforts).

 

 

And this is the ONLY comparison point that's in any way valid, is that CFD which just happens to be for the 120 and again this is ball-park comparable to an SD-10, but much closer ball-park than building up from a list of shapes - there's no need for comparison between in-game entities since this is inappropriate.

 

 

 

As for the shape of the graph itself - the SD-10 in-game has the same drag coefficients for subsonic and high supersonic mach numbers. But pretty much every missile out there has a higher supersonic drag than subsonic, at least up to the mach numbers we're concerned about.

 

 

We don't have enough information about the rocket motor configuration of the SD-10. We know it's boost-sustain, but the only equivalent rocket motor we have to compare it to is the AIM-7, for which we do have information.

The SD-10 is a much newer missile, and it may actually have a higher fuel fraction and other good things that will give it better performance than the AIM-7.

However, the boost-sustain stages are set up with a long boost and short sustain, which isn't how things are usually done and doesn't even make a lot of sense since all boost would get you to a higher peak speed and those extra 4 sustain seconds become irrelevant. Also makes the rocket easier to build with a single grain instead of dual grain.

 

So ultimately you are guessing it’s current behaviour is incorrect due to how the most comparable nato missile is designed since so much of its internal working is unknown to you and general public? Not dismissing your research but just trying to understand how much of the data provided is exactly from SD-10 and how much is filled gaps using similar but different missiles.

[LF_Luftmanu]

I can make dinner twice this week with the amount of salt in this thread.

[GGTharos]

So ultimately you are guessing it’s current behaviour is incorrect due to how the most comparable nato missile is designed since so much of its internal working is unknown to you and general public? Not dismissing your research but just trying to understand how much of the data provided is exactly from SD-10 and how much is filled gaps using similar but different missiles.

 

 

No, ultimately I'm comparing drag coefficients, so don't need to know anything about internal workings.

You could argue that comparing these things so directly isn't super-accurate, and I agree - but we don't need super-accurate here because the SD-10 behaves outside of the realm of physics wrt drag coefficients. In other words, it's so far out there that it cannot be correct.

 

 

Anyway Deka has responded, ED has responded, all of this will get sorted out.

[GGTharos]

I can make dinner twice this week with the amount of salt in this thread.

 

 

You could salt a lake.