High-fidelity missile simulation

[Redeye 43]

The old AIM-9B had a very simple spin scan seeker that caused its characteristic 'sidewinding' motion. Later variants had different seekers that conferred different behaviors which are not currently accurately simulated; countermeasure resistance, multi-aspect behavior, etc. Radar-guided missiles that used conical scanning also exhibited these not perfectly straight paths. Accurate missile seeker simulation would greatly improve the behavior of weapons in DCS.

[Mike_Romeo]

All air to air missiles are going to be reworked.

 

[okopanja]

@Mike_Romeo please notice that this highly flammable topic is closed. It would be cool if the aggregated topic per each missile could be opened.

[Mordant]

I think its worth noting that these types of things can be somewhat difficult to get pinpoint info on. Obviously, people can find plenty of Sidewinders being launched in live fire exercise and I definitely would appreciate it if they don't always go in a perfectly straight line and actually acted like a Sidewinder irl but theres some info we just can't get. Like others have said, it's being worked on, and DCS(as I'm sure everyone knows) is almost constantly being worked on. I wouldn't discount it for the future as the -120 and -27's have been updated and improved already.

Smooth skies,

Mordant

[Redeye 43]

On 12/2/2021 at 7:05 AM, Mordant said:

I think its worth noting that these types of things can be somewhat difficult to get pinpoint info on. Obviously, people can find plenty of Sidewinders being launched in live fire exercise and I definitely would appreciate it if they don't always go in a perfectly straight line and actually acted like a Sidewinder irl but theres some info we just can't get. Like others have said, it's being worked on, and DCS(as I'm sure everyone knows) is almost constantly being worked on. I wouldn't discount it for the future as the -120 and -27's have been updated and improved already.

Smooth skies,

Mordant

The old seekers probably have their whole blueprints out there - for newer or badly-documented systems, approximations can at least be made. The early AIM-7s also had weird behavior, iirc, because they used two spinning horns instead of a slewing antenna? My memory isn't the best on it, anyway. I'd at least appreciate an advanced missile simulation engine so that missiles for which data is available can be simulated accurately. It'd be especially fun to see the eccentric twisting of an AIM-9B.

Edited December 5, 2021 by Redeye 43

[Northstar98]

On 12/5/2021 at 5:44 AM, Redeye 43 said:

The old seekers probably have their whole blueprints out there - for newer or badly-documented systems, approximations can at least be made.

Yes, for the AIM-9B we know it has a simple spin-scan, AM logic seeker, which employs a spinning reticle, that spins at 70 Hz. It uses an uncooled Lead-Sulfide detector. With a total FOV of 25 °, IFOV of 4 ° and a tracking rate of 11 °/s.

Sidewinders up the L used this spin-scan AM logic, though with differing tracking rates and cooling.

For the AIM-9L and M, they switch to a conical scanning, FM logic seeker, which spins at 125 Hz, using a cooled Indium-Antimonide detector.

The P-4/P-5, uses a similar seeker, but with a reticle that spins at 100 Hz.

For more about spin-scan, AM logic trackers and conical-scanning, FM logic trackers, I'd recommend this and this as a source for how they work (which also includes things like countermeasures).

On 12/5/2021 at 5:44 AM, Redeye 43 said:

The early AIM-7s also had weird behavior, iirc, because they used two spinning horns instead of a slewing antenna?

Yes, AFAIK up to the AIM-7M, the Sparrows uses a system kinda like conical scanning, using a spinning antenna (though I think you are correct in that it's 2 spinning antennae instead of something more typical, just trying to find a source), AIM-7M (and Skyflash and Aspide) uses an inverse monopulse seeker.

EDIT: found images for the AIM-7F and AIM-7M seekers:

• AIM-7F seems to have a rectangular slotted, planar array, mounted on a gimbal, but is described as using conical scanning.
• AIM-7M is a circular slotted planar array (once again, mounted on a gimbal), much like the AN/APG-65/73. As mentioned above though, this uses an inverse monopulse seeker instead of a conical scanning system.

There is also a picture of a supposed AIM-7E seeker, but the image is identical to the AIM-7M, which shouldn't be the case (AIM-7E should have vacuum tube technology instead of solid-state electronics).

Source (scroll to the bottom).

On 12/5/2021 at 5:44 AM, Redeye 43 said:

My memory isn't the best on it, anyway. I'd at least appreciate an advanced missile simulation engine so that missiles for which data is available can be simulated accurately. It'd be especially fun to see the eccentric twisting of an AIM-9B.

+1 and a certain other 'lite' simulator had missiles that did these motions, at least for applicable missiles.

And wouldn't the frequency of this 'twirling' motion just be determined by the frequency of rotation of the seeker? At least for the all the sidewinders this applies to, this number is known.

Edited December 27, 2021 by Northstar98
spelling

[Redeye 43]

15 hours ago, Northstar98 said:

-bits snipped-

Yes, for the AIM-9B we know it has a simple spin-scan, AM logic seeker, which employs a spinning reticule, that spins at 70 Hz. It uses an uncooled Lead-Sulfide detector. With a total FOV of 25 °, IFOV of 4 ° and a tracking rate of 11 °/s.

For the AIM-9L and M, they switch to a conical scanning, FM logic seeker, which spins at 125 Hz, using a cooled Indium-Antimonide detector.

The P-4/P-5, uses a similar seeker, but with a reticule that spins at 100 Hz.

Yes, AFAIK up to the AIM-7M, the Sparrows used conical scanning using a spinning antenna, AIM-7M (and Skyflash and Aspide) uses an inverse monopulse seeker.

Seems to me like this is all we need to know for accurate missile simulation. Basically make a 70 Hz spinner, give it sensitivity fitting for a lead sulfide detector, set its FOV, IFOV and tracking rate, and you're done. For any other missile, adjust fittingly. Monopulse seekers like the AMRAAM, Phoenix and 7M on can be simulated a lot more simply, but at least some work should be done to mimic the action of older missiles, imo.