correct as is DCS Aim-7 Sparrow Potentially Underperforming

[NineLine]

But you guys see where Маэстро is coming from right? This is how our development works, we try very hard to work with whatever available sources we have, and cut out the opinions as much as possible, that means even if you think it might be a common sense conclusion, it is still only opinion. Lets keep this in mine that our devs love this stuff, and enjoy the work, probably as much if not more than you guys love this stuff. They want as real as possible which as we all know is very tough to do with such limited information.

[dundun92]

11 hours ago, near_blind said:

Unless I'm tripping, the 1976 SMC, the 1977 SMC, and the 1984 Weapons file all agree on a boost of 4.5s at 5750 lbs and a sustainer for 11s at 1018

It also happens that if you use take numbers at face value, you get an absurd specific impulse of > 300s as I mentioned, which is physically impossible for this kind of motor. As GG said, you either have to cut down sustain time and give the boost some of its propellant, or (what I had mentioned) cut down the boost time. Either fits the data, but both require one of the SMC numbers to be modified for burn time and boost/sustain mass fraction. The total prop mass (135lb) is already known from other reliable sources (yellow book etc), so theres no negotiating with that.

Edited June 3, 2022 by dundun92

[Маэстро]

On 6/3/2022 at 6:31 PM, GGTharos said:

Hi Maestro, normally I like to run tests before I present anything but ... I don't have access to anything until August - certainly I failed to do at least my back-of-the-envelope calculations this time, but also I'm not concerned with Mach 4 in practice , it's just a reference point

Thanks for responding.

I have seen the same sources then.  I don't know that Fleeman has the right numbers for the motor, I'm inclined to trust that source but on the other hand there are no guarantees.

Pilots do know, they have resources for this sort of thing ... but they may not be able to talk about it:  Vault documents and also debriefs from real and simulated combat make a lot of data available, data from instrumented shots is likely available.

I have no doubt with respect to your skills and knowledge, just FYI - I am bringing this to your attention as IMHO the missile is running a little slower than I believe it should; not my much, mach 0.2 or so.  It's also possible that this is caused by guidance issues, wasting speed in unnecessary maneuvers in the boost stage.

 

Hi GGTharos, good if pilots have data from instrumented shots, but even if they be able to talk about we would need data for set of shots to understand how the avarage missile looks like.(There is always some uncertainity due to different air and motor charge temperature, some devation on total impulse, hence there may be deviation on that Mach 0.2 or so)

Regarding AIM-7 guidance - it's not related thing(and it works correct). If we talking about top speed/ballisitcs we should assume that missile fly stright ahead without any maneuvers. Manuvering is a separate case.

BTW I'have found that nozzle exit area was not defined for AIM-7 family in OB. It was fixed internally, but not released. We will include it into the next patch. That will give missile additional 0.1 Mach of top speed

Another interesting thing is AIM-7 radome. It's different for an old and newer versions, see attached. Right now we have drag of old radome with a higher Length/Diameter ratio for all aim-7 versions. I plan to run CFD someday to find out the difference in zero-lift drag value. Think it may be 5-10% higher for M/H/P versions of missile.

 

[GGTharos]

Thanks for looking into this deeper.     Yep, I would expect that this dome change would increase drag, but in exchange the radar image is probably less refracted and possibly increases sensor accuracy.

[Exorcet]

For those interested a video with some Sparrow test data. AIM-7D (not in DCS) and E (useable in DCS):

Test at ~17:30+

 

[Cmptohocah]

4 hours ago, Exorcet said:

For those interested a video with some Sparrow test data. AIM-7D (not in DCS) and E (useable in DCS):

Test at ~17:30+

 

Very informative video.

[nighthawk2174]

On 6/6/2022 at 4:39 AM, Маэстро said:

Hi GGTharos, good if pilots have data from instrumented shots, but even if they be able to talk about we would need data for set of shots to understand how the avarage missile looks like.(There is always some uncertainity due to different air and motor charge temperature, some devation on total impulse, hence there may be deviation on that Mach 0.2 or so)

Regarding AIM-7 guidance - it's not related thing(and it works correct). If we talking about top speed/ballisitcs we should assume that missile fly stright ahead without any maneuvers. Manuvering is a separate case.

BTW I'have found that nozzle exit area was not defined for AIM-7 family in OB. It was fixed internally, but not released. We will include it into the next patch. That will give missile additional 0.1 Mach of top speed

Another interesting thing is AIM-7 radome. It's different for an old and newer versions, see attached. Right now we have drag of old radome with a higher Length/Diameter ratio for all aim-7 versions. I plan to run CFD someday to find out the difference in zero-lift drag value. Think it may be 5-10% higher for M/H/P versions of missile.

 

I'd seen some documents reference two different nose cons for the 7F one that is better for the sensor and one better for aero performance i'd just never seen the difference.  Do we know which one was in more common use?

 

edit:

Didn't the 7M get another redesigned nose again from the 7F?  From just one quick image grab it seems that it's closer in shape to the older but more aerodynamic nose cone:

Edited June 13, 2022 by nighthawk2174

[GGTharos]

On 6/6/2022 at 6:39 AM, Маэстро said:

Hi GGTharos, good if pilots have data from instrumented shots, but even if they be able to talk about we would need data for set of shots to understand how the avarage missile looks like.(There is always some uncertainity due to different air and motor charge temperature, some devation on total impulse, hence there may be deviation on that Mach 0.2 or so)

Regarding AIM-7 guidance - it's not related thing(and it works correct). If we talking about top speed/ballisitcs we should assume that missile fly stright ahead without any maneuvers. Manuvering is a separate case.

BTW I'have found that nozzle exit area was not defined for AIM-7 family in OB. It was fixed internally, but not released. We will include it into the next patch. That will give missile additional 0.1 Mach of top speed

Sorry, getting back to this piecemeal - I'm travelling a lot lately.   So, another thing that might help is that in the game, the drop from boost to sustain is instantaneous, but in actuality you'd have a 0.2-0.3sec gradient that would ensure you're getting trust above that of the sustainer, even if for a very short time.

[F-2]

https://apps.dtic.mil/sti/pdfs/ADA486826.pdf
https://apps.dtic.mil/sti/pdfs/ADA107003.pdf

 

useful DTIC reports

[F-2]

On 5/31/2022 at 2:37 PM, dundun92 said:

So for the 7F/M, the problem is that there seems to be multiple sources that give different boost times; the SMC/SAC puts it at 4.5s w/ 5700 lbs of thrust. The 1984 weapons file puts it at 5750 lbs thrust for 4s. Theres also this source, im unsure of the origin, but it puts it at 3.5s boost, which I think is the correct one:

null

The reason the SMC's 4.5 sec burn time seems suspect is that when you do the math on the thrust per the SMC (25.5 kN) and mass flow rate (38 kg of boost fuel, accounting for the flipped boost/sustain prop mass in the SMC), you get an ISP of ~312s for the boost, which is very much out of whack. if you reduce the burn time to 3.5s, the ISP drops to 241s; which is a much more sane value.

For reference, ED's sparrow has a 3.7s boost, 38.48kg fuel mass, 25.1 kN thrust, and 247s of ISP, which lines up with the SMC boost motor mass and a reasonable ISP. So at least IMO, the AIM-7 motor is pretty good RN compared to what we know about it IRL.

Does anyone know if this seeker range and gimbal is simulated for the AIM-7F?

Edited August 25, 2023 by F-2

[GGTharos]

It isn't, and besides it's a range against a specific RCS target with designation from a specific radar.  Both of which are not present in the excerpts you posted.

[MysteriousHonza]

Would be pages from british doc about 7F viable? TOF under specific conditions. There are some on wt forums, iam trying to get info from what exactly it is and if its public doc, just not digital.

[BIGNEWY]

please do not share any docs here, PM if you are not sure and remember our 1.16 rule at the top of the forum

thanks

[Notso]

Disregard.  Moved to its own thread....  

 

Edited January 15 by Notso

[marmor]

On 1/11/2024 at 10:10 AM, MysteriousHonza said:

Would be pages from british doc about 7F viable? TOF under specific conditions. There are some on wt forums, iam trying to get info from what exactly it is and if its public doc, just not digital.

It's from the Tornado F3 tactics Manual. Those are ACMI flyouts.

Dunno if someone can test them

null

 

YES its declasssified

[Hobel]

Have you noticed the new notes?
I think it was partly 30kg less

Zitat

• Weapons. AIM-7E/E2 mass decreased.