Why do radar missiles crash into the ground if you fly very low?

[AgasTheBrave 100]

One of the most common tactics to evade radar-guided missiles is to fly extremely low and, in most cases, the missile will simply crash into the ground; even when flying over a flat surface like a lake.

I was wondering, why is that? Is the radar losing track of you due to the proximity of the ground? If so, why, when it's a pulse-doppler radar. Or, is the missile's proportional navigation system wrongly calculating its approach, "trying" to get underneath the plane for some reason and ending up kissing the ground? And if that's the case, again, how come? I don't see missiles doing that at higher altitudes.

And, lastly, is this realistic, or is it just a game mechanic to make evading said missiles easier?

Thank you!
O7

Edited June 18, 2023 by AgasTheBrave

[tripod2008 594]

11 minutes ago, AgasTheBrave said:

is this realistic, or is it just a game mechanic to make evading said missiles easier?

It is accurate to a degree, though its impact is overstated for gameplay purposes for more modern missiles, though they are still effected, though generally at a lower altitude.

 

The actual mechanic that causes the effect depends on the specifics of the missile's Seeker / Guidance mechanism and the intercept scenario. IRL the Proximity fuse would also need to be taken into account for functioning but that isn't modeled outside a generic radius of action in WT, which themselves are reduced to ensure the effective function of the Warhead in game due to how only the explosive mass of the warhead is taken into account, and the other aspects of the warhead e.g. weight & diameter of the continuous rod's elements / weight of the fragmentation jacket / number of pre-forged fragments is abstracted entirely. and that by itself the power of 1kg of TNT is understated somewhat in game.

 

But honestly its a pretty minor issue in terms of radar modeling in comparison to others like how RCS is a constant value and doesn't change with crossing angle. Though as with other things WT continues to receive new mechanics and update existing ones so it may well be changed in the future when other mechanics are added.

 

With the implementation of IRCCM on the recent Su-25T / Su-39 its looking like ECM pods would be similarly powerful so having other hard counters would be less necessary.

[_Iluminas_ 3,769]

I think its just the missle calculating where the target will be at impact and thus going into the ground when the plane is steering towards the ground

Edited June 18, 2023 by _Iluminas_

[somebody_Else 776]

4 hours ago, AgasTheBrave said:

One of the most common tactics to evade radar-guided missiles is to fly extremely low and, in most cases, the missile will simply crash into the ground; even when flying over a flat surface like a lake.

I was wondering, why is that? Is the radar losing track of you due to the proximity of the ground? If so, why, when it's a pulse-doppler radar. Or, is the missile's proportional navigation system wrongly calculating its approach, "trying" to get underneath the plane for some reason and ending up kissing the ground? And if that's the case, again, how come? I don't see missiles doing that at higher altitudes.

And, lastly, is this realistic, or is it just a game mechanic to make evading said missiles easier?

Thank you!
O7

 

Multi-path echo.

 

The radar signal is bouncing from target plane to the missile, but its also reflecting off the ground before it reaches the missile.

 

Means the missile see's apparent "ghost" targets that appear to be underground from its perspective, the missile gets confused.

[AgasTheBrave 100]

4 hours ago, tripod2008 said:

It is accurate to a degree, though its impact is overstated for gameplay purposes for more modern missiles, though they are still effected, though generally at a lower altitude.

 

The actual mechanic that causes the effect depends on the specifics of the missile's Seeker / Guidance mechanism and the intercept scenario. IRL the Proximity fuse would also need to be taken into account for functioning but that isn't modeled outside a generic radius of action in WT, which themselves are reduced to ensure the effective function of the Warhead in game due to how only the explosive mass of the warhead is taken into account, and the other aspects of the warhead e.g. weight & diameter of the continuous rod's elements / weight of the fragmentation jacket / number of pre-forged fragments is abstracted entirely. and that by itself the power of 1kg of TNT is understated somewhat in game.

 

But honestly its a pretty minor issue in terms of radar modeling in comparison to others like how RCS is a constant value and doesn't change with crossing angle. Though as with other things WT continues to receive new mechanics and update existing ones so it may well be changed in the future when other mechanics are added.

 

With the implementation of IRCCM on the recent Su-25T / Su-39 its looking like ECM pods would be similarly powerful so having other hard counters would be less necessary.

Hmmm, wait; so if I got it right, basically, the missile's proximity fuse triggers because it flies too close to the ground?
 

3 hours ago, _Iluminas_ said:

I think its just the missle calculating where the target will be at impact and thus going into the ground when the plane is steering towards the ground

I thought so too initially, but it happens even if you are in level flight, without pointing the aircraft towards the ground.
 

17 minutes ago, somebody_Else said:

 

Multi-path echo.

 

The radar signal is bouncing from target plane to the missile, but its also reflecting off the ground before it reaches the missile.

 

Means the missile see's apparent "ghost" targets that appear to be underground from its perspective, the missile gets confused.

Hmmm, very interesting, but wouldn't the radar be able to "discern" between the target and the ground thanks to the doppler effect?

[somebody_Else 776]

5 minutes ago, AgasTheBrave said:

Hmmm, very interesting, but wouldn't the radar be able to "discern" between the target and the ground thanks to the doppler effect?

 

The ghost signals have already been doppler shifted by the target plane, so the signal shouldn't be all that different to the real one.

 

And its been shifted enough that it won't be filtered out as ground clutter.

[AgasTheBrave 100]

5 minutes ago, somebody_Else said:

 

The ghost signals have already been doppler shifted by the target plane, so the signal shouldn't be all that different to the real one.

 

And its been shifted enough that it won't be filtered out as ground clutter.

I see, yeah, I don't know enough about radars to understand exactly how that works, gonna do some reading on it. Thanks! O7

[Speggn 2,528]

Also dont forget, we do not have "smart" modern missiles in the game. Those we have are from the 70s and 80s. No fancy computers in there.