Laser beam riding missiles lose lock when the laser is redirected.

Hello,

It's been a while (quite some years) since we are no longer able to shoot 2 or more missiles, each one at different timing and target while using laser designation, without having these missiles lose it's lock on the laser beam if the beam is re-oriented.

When DCS was an early version (1.2.x) you could fire 2 or 3 vikhrs or 2 or more KH-25ML or any other types of laser guided missiles at a target and all the missiles would be listening to the laser pointer no matter how slow/fast would you steer your laser all the way to the edges of the tracking system.

Now, if you slightly move your laser while having a missile in the air, the missile immediately loses laser track with no way of getting it back and the missiles goes sticking into the mud. Whatever happened to the laser guided missiles tracking system doesn't seem normal (maybe an unreported bug) for so much time and nobody seems to talk about it. In reality, you may fire all your laser guided missiles and they should all follow to the laser signal continuously (as long as the laser is still illuminating) when the laser is moved. This is very useful with the correct firing timings allowing you to hit targets one after another by simply moving your laser designator to the next one after each missile hits.

This only happens to themissiles fired from aircraft (Su-25, KA-50). When shooting a laser missile from a ground unit, the missile remains slaved to the laser even if you move the pointer it at the moon or the sky, which makes me wonder how can that missile still follow a laser that doesn't reflect of anything, yet this may be another discussion.

You can't do this in DCS anymore as long as the missile loses laser lock whenever you make an adjustment to the laser's position. Is this normal?

Regards!

The beam guidance pattern for the Vikhr is quite small and constantly shrinking on a timer after firing to produce a constant size at missile. You should be able to do very gradual movement as would normally be associated with the parallax due to platform motion or tracking a moving vehicle but rapid motion will cause the missile to leave its lane and go dumb. It's not able to maneuver to remain within the control zone if the zone shifts too quickly.

It's not like an LGB which has the sensor looking forward with a wide field of view looking for a spot. The sensors are in the tail and are sort of bouncing off the walls of a laser tunnel emitted from the platform. Even laser-seeking (instead of beam-riding) weapons can't follow a spot motion which is too high.

The Vikhr is also a one-axis control system, the spiral allowing its one fin to do lateral and vertical maneuvers every quarter roll. This limits its instantaneous maneuver ability to whatever roll orientation it is currently.

I'm guessing that other beam-riding systems in vehicles are modeled either very simply (over performing) or are sophisticated enough to decouple the aiming axis from the communication to missile axis (Tunguska?).

I don't know about re-acquire prospects. It would be interesting to know if Vikhr can recover from a short loss of signal (e.g. obstacle blocks laser for a few seconds).

The beam guidance pattern ...

It's not like an LGB which has the sensor looking forward with a wide field of view looking for a spot. The sensors are in the tail and are sort of bouncing off the walls of a laser tunnel emitted from the platform. Even laser-seeking (instead of beam-riding) weapons can't follow a spot motion which is too high.

Got it!

The Vikhr is also a one-axis control system, the spiral allowing its one fin to do lateral and vertical maneuvers every quarter roll. This limits its instantaneous maneuver ability to whatever roll orientation it is currently.

Yeah, I knew about how it was designed to maneuver through constant rolls and thus constantly oscillate it's maneuvering fins to correct the trajectory, but still, following the laser beam is the problem (and now I've learned from you), otherwise even if slowly maneuvering, if the lock on the laser wouldn't be lost this missile would've had more performance in combat.

I'm guessing that other beam-riding systems in vehicles are modeled either very simply (over performing) or are sophisticated enough to decouple the aiming axis from the communication to missile axis (Tunguska?).

Yeah, the Tunguska might be a good example of keeping the missile follow (be slaved) to the laser no matter how sharply the laser gets moved, but all other ground vehicles using laser missiles behave the same.

I don't know about re-acquire prospects. It would be interesting to know if Vikhr can recover from a short loss of signal (e.g. obstacle blocks laser for a few seconds).

You've just read my mind!:)) I was also wondering if that might be possible in the end!

Ok, so now I've got it with Vikhr, but what about KH-25ML when fired from the KA-50. From just one or 2 tests that I've done (so I definitely have to test it more to confirm) I have the impression that the KH-25ML fired from KA-50 also loses track on the laser beam once it's quickly moved. It simply doesn't want to follow it anymore and not re-acquire track on it again, while when fired from the Su-25, the missiles seems to listen to the laser no matter how you play with it. Again, I must retest this to confirm, but that's what I apparently witnessed.

Cheers and regards!

I just tried Vikhr and I was able to redirect on a 7-8km shot to a target 550m lateral which is the practical limit of how fast I can really slew the Shkval. I'm using the directional keys. The axes can move the Shkval much faster than the keys.

The Shkval via axes is not satisfactory. The minimum output that moves it is 6/100ths so the minimum traverse rate is still quite high. The rate doesn't change between 7x and 23x view which you think it would in the real system. Reducing the rate by 7/23rds when in narrow FOV would make fine adjust much easier.

Anyway, I found the Vikhr would track at 20/100ths slew speed when axis controlled which was much faster than I thought it could handle. I think 1-2 pipper diameters per second would be a reasonable limit of adjust during fire.

One would expect that the risk of over steering the missile would grow as the missile gets farther away. Each degree of LOS change represents more meters of lateral translation the more distance is between the source and the sensor.

Kh-25ML is laser-seeking like a Hellfire. It is working today in a different way than it was last time I checked. I am able to change target while missile is in flight. I have no found the limits when shifting a large amount though. I am guessing it is similar to very fast rates of Shkval when under axis control (even glass nose weapons have a laser spot angular limit of some kind).

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Kh-25ML is laser-seeking like a Hellfire. It is working today in a different way than it was last time I checked. I am able to change target while missile is in flight. I have no found the limits when shifting a large amount though. I am guessing it is similar to very fast rates of Shkval when under axis control (even glass nose weapons have a laser spot angular limit of some kind).

Hmm, that's interesting cause just now I've tested the KH-25ML, the KH-29ML and the S-25L and except the S-25L which still remains locked to the laser beam no matter how fast you play with the laser slew, the other two lose lock and go ballistic instantly after I start slewing the laser, even if I move the pointer 1 meter away from a target to any direction on the ground these ones lose lock on the laser and fall.

For example, it was very hilarious to see the KH-29L listening to the laser which was pointed at a tank without a lock because I fired the missile from a higher distance than the shkval was able to lock onto (further than 10km) and immediately after the shkval acquired the target the KH-29L instantly started to fall although the laser didn't have to move too much to correct it's position when the shkval acquired that target. So, just for the tiny adjustment to the laser made by the shkval, made the missile lose lock.

Can you provide a track of your KH-25ML and KH-29ML fired from Su-25T's and how they follow your laser flawlessly?

Thanks!

Kind regards!

Here, in this track we can clearly see that both the KH-25 and KH-29 laser missiles lose laser track once the slew rate goes above a certain value. Indeed, I have also found that these missiles don't lose lock until the slew is above some rate, yet that rate seems quite low to me and I guess it's quite close to that of where the Vikhrs also lose their track on the laser.

KH-25L and KH-29L lose laser track above some slew rate.trk

The missile that still follows the laser like a king no matter the slew rate (seems to have no limit to this) and still manages to "crawl with one hand" is the winning S-25L. This missile follows the laser no matter what until it self-detonates if it's unable to steer fast enough to align itself with the laser's designation. I doubt that the S-25L has anything special. Normally the KH-25L and KH-29L should be higher tech than the S-25L, so I suppose something is still wrong and I doubt it's regarding the S-25L.

Cheers and regards!

Watching the track I see Kh-25L hitting where Shkval is pointed when you guide with a modest tracking rate. Perhaps we are seeing different results from the same track?

Watching the track I see Kh-25L hitting where Shkval is pointed when you guide with a modest tracking rate. Perhaps we are seeing different results from the same track?

Seeing different results in a track is not unusual. More than once, I've played a track to watch a takeoff or landing, and the track shows my aircraft crashing after a good takeoff or landing. This has been a known issue with tracks for quite a while. I haven't been able to find any explanation for why it happens at random.

Watching the track I see Kh-25L hitting where Shkval is pointed when you guide with a modest tracking rate. Perhaps we are seeing different results from the same track?

OK, but how fast is moderate? I mean, from my opinion there shouldn't be any reason to lose track of the laser at all. We understand about the Vikhr, but now all laser air to ground missiles (except the S-25L) have the VIkhr's limitation of losing track if the laser slews more than "X" degrees per second?

What about the S-25L? That poor tech missile has no trouble following the laser even if it were slewing at almost infinite degrees per second. So, are you with me? There's definitely something not suppose to be happening. For me, this is only a problem of how the missile's laser tracking is modeled in DCS and I doubt that the real KH-25L or KH-29L would lose track if the laser or the skhval (which the laser is slaved to) is slewed at it's maximum rate on the real plane. If in reality it would've been the case we see in DCS, I'm pretty confident that the engineers would've found a solution to this by either not letting the slew rate go past "X" degrees/s where the lock may become vulnerable or re-work the missile's systems until the missile stops losing laser track due to slew rate. It would be embarrassing for the real pilot to see his missile go dumb just because he slewed too quickly. This can't happen in reality, although DCS might want to let us think that way. I mean I wish I could agree, but I won't until this limitation would be confirmed by real military personnel (pilots, engineers) who had experiences with the KH-25L, KH-29L and S-25L.

Kind regards;)!

All of your slews that went at about 1 degree per second, almost all of them in the track. I think one was super fast and didn't allow Kh-25 to follow. I could think of a good reason to filter out some returns based on speed. If a helicopter or ground team was designating and there were scattered reflected or ground returns you wouldn't want the missile too eager to pick them up. Then there is the physical limit to torque the seeker gyro over. Naturally it must be capable of following the target as the missile lofts quite quickly.

"The 24N1 seeker has an IFOV of 2º and a Field of Regard of 30º. A proportional navigation control law is used for terminal homing. Post launch the autopilot is programmed to fly a climbing trajectory to preclude the missile exhaust obscuring the target view from the launch aircraft."

I expect the missile wants to begin track before launch and nutates a pattern to maintain track. If it lacks a reacquire program that scans the whole space I could see spot motion faster than its IFOV per nutation cycle time breaking track. Maybe the real Shkvals are much easier to be careful with to prevent overly rapid slewing?

S-25L seems too good to be true, mostly its insane glide performance. Kh-25 does this very pronounced G-bias loft which seems delicate to spot motion. It's a fat missile with tiny fins and the spot is on the lower edge of its view for the loft portion.

I can't say how both should really perform. My gut reaction is that S-25L is much more robust than I'd expect and Kh-25L is slightly more delicate than I would expect the engineers would tolerate.

Interesting https://www.youtube.com/watch?v=cX1Z5vX2Kws it looks like it can be set direct and top attack and may be used in mixed pairs to have a dual effect. Right now we're getting the top attack one. It sadly doesn't showcase any midfight redirection.