Chaff

[Essah]

So I've been wondering how exactly chaff works.

as far as I understand:

Chaff is a whole lot of metal strips released from a canister in the aircrafts countermeasure launchers. When released they reflect a huge amount of radar energy due to the large surface of the many small strips and therefore looks more like an airplane to a radar than the actual airplane does (Missile: the largest radar cross section must be the aircraft right?)

This decoys active radar missiles as their internal radar locks on to the chaff instead of the airplane itself and tracks that until it disperses.

 

what I don't understand is how this works with Semi autonomous radar missiles. They're guided by the radar energy reflected by the target when its painted by the host aircraft's radar. so in my logic when chaff is released

a) your aircraft's radar would either lock on to the chaff until it disperses instead of the actual enemy aircraft and track the missile to that

or

b) your radar would keep tracking the actual airplane and the chaff would have no effect at all with the missile still homing into energy reflected from the airplane being painted, not the chaff.

 

however none of these happens.

your radar stays locked on to the aircraft but the missile (sometimes) tracks the chaff

why is that?

 

let me know if I need to clarify my question.

 

Thanks in advance

[zakobi]

It's a game, so i'm guessing they took some shortcuts so not to make to too complicated.

 

In reality, chaff pieces are in different lengths, as to accommodate different radar wavelengths. Err, Wiki is your friend for it, i can't remember the exact answer :P

[sobek]

As zakobi said, i wouldn't try to guess at RL behaviour of a system from how it is modelled in a game, especially in a survey sim. Modern radars use rather sophisticated signal processing that can distinguish between the returns generated by chaff and those generated by a plane and reject the chaff. Same goes for modern missile seeker heads, i guess.

[Bimbac]

Hello,

 

I'll try to answer your question in a most precise manner I am capable of.

 

1) Chaff stripes act as a half-wave dipole, and due to some physics laws these cause an EM interference preventing the radar to get a precise lock. Chaff is one of the oldest methods of anti-radar countermeasures, first used during WW2.

 

2) Even if the tracking radar is able to maintain the lock and is guiding a semi-active missile to the target, the missile antenna and proximity fuse get overwhelmed with false echoes, therefore not functioning properly (either losing the lock or explode prematurely).

 

3) I am not an expert on Russian missiles, so I can talk just about physics, although it applies to anybody on this planet :). Missile in command mode could theoretically still follow a locked target, but when coming to terminal phase (using its own sensors), the aforementioned problem would apply to it in exactly the same way.

 

In my opinion, it will take years to properly simulate a real-life electromagnetic environment within a computer simulation, but when that day comes, we will definitely see a much more realistic sensor and missile behavior. :thumbup:

 

Regards!

[Essah]

Thanks guys, especially Bimbac. Thats good enough answer for me, didn't think about the proximity fuse. Makes a lot of sense.

[nscode]

b) your radar would keep tracking the actual airplane and the chaff would have no effect at all with the missile still homing into energy reflected from the airplane being painted, not the chaff.

 

Your radar is tracking the target and illuminating it with its beam. The beam however, is not like a laser, but more like a flashlight. Even though the center of the beam is around the target, it is still wide enough to "light up" chaff.

[Essah]

Your radar is tracking the target and illuminating it with its beam. The beam however, is not like a laser, but more like a flashlight. Even though the center of the beam is around the target, it is still wide enough to "light up" chaff.

 

so logically chaff is only working as long as it is reasonably close to the targeted airplane and therefore still within the beam. when it drifts farther away it disappears outside of the beam

(if it hasn't scattered already by then)

 

is the missile more likely to be decoyed when it's closer to the chaff or does it have no effect?

[Bimbac]

It does. Energy dissipates with the distance squared, so closer means more powerful.