Stealth vs ECM

[artik]

We all are talking about 5th generation fighters how they are stealthy...

Stealth:


- They are costly (F-22, F-35, B-2)
- Not really available - currently only few F-22, B-2 operational around + several stealthy drone models.
- Not 100% fault proof - long wave radars, IR emission, visual detection and so on that most likely being developed and less known

Now as cheaper alternative we can use ECM... Missile heads usually have simpler and less powerful radars and easier to fool - so if you know how, you generally can. So:

ECM:

- Much cheaper - just a smart computerized pod
- Can be easily upgraded for new threats (new pod or even software upgrade)
- Do not require significant changes in the aircraft, if at all
- Almost no impact on the flight characteristics (besides some drag)
- Can be installed almost on any aircraft
- Most likely get you to the merge - eliminating all stealth advantages of the opponent

Even Russia, that has traditionally less efficient avionics and electronic system produces and exports ECM pods that (at least according to the specs) handles AMRAAM missiles.


So what is more effective*:

- Have few stealthy drones/aircraft for special missions and sophisticated ECM on 4th++ generation aircraft
- Invest into stealthy air force

* By effective I mean - having the most effective air force for a given budget constraint


Some samples:

MiG-29K with IAI ECM Pod: https://www.youtube.com/watch?v=NhN7_L3R6uU#t=450

MiG-21 Bison Carrying an IAI ECM Pod.

[GScholz]

ECM also broadcasts your position to everyone with even the most rudimentary EW units. ECM is something you use after you have been detected. Stealth prevents detection. The Russian R-27 and newer missiles as well as the Sparrow and AMRAAM has home-on-jam capabilities.

[Vraciu]

ECM also broadcasts your position to everyone with even the most rudimentary EW units. ECM is something you use after you have been detected. Stealth prevents detection. The Russian R-27 and newer missiles as well as the Sparrow and AMRAAM has home-on-jam capabilities.

Stealth DELAYS detection or reduces signature.  It is not a panacea.

[bozon]

artik,
ECM is only as good as the knowledge of the threat it is designed to defeat. If you know the enemy radar very well, you can tailor sophisticated methods to fool it completely. In reality, one side is building the radar and its opponent build the ECM. The latter does not posses perfect knowledge of the radar system, though that is not always true.

ECM and ECCM (i.e. methods to defeat ECM) evolve very fast, so effectiveness is a big unknown and may change all the time. ECM capabilities are closely held secrets. Actually one of the most secret pieces of equipment on the plane. In addition, there is ECM support from the ground and other planes on special EW missions. The latter two can often defeat radars by brute force - that is by very high power transmission that blinds enemy radars. It's the equivalent of shining a spotlight into your eyes. This will work on any radar given sufficient power concentrated in the right frequencies and the right direction. More elegant and sophisticated methods are preferred though. However, such support is not always available, especially not in deep strategic strikes. For such missions self-ECM and stealth will have to do.

In 1973 the IAF took a beating from the soviet SAMs employed by the Syrians and Egyptians. American ECM pods that the US used in Vietnam were handed over to the IAF but proved to be worthless. Israel decided to develop its own EW capabilities and 10 years later the IAF destroyed over 20 Syrian SAM batteries without losing a single plane, clearing the whole Lebanon airspace from SAM threat for the rest of the war. IAF conducted several operations in Syrian airspace in the time since, and the Syrian SAMs and radars were ineffective during all of them. IAF still installs its own ECM and EW systems in the American planes it gets, much to the dismay of some US companies. With the F35 IAF was promised that it will get planes ready to receive its custom Israeli avionics and systems right off the production line, but I heard talks that the US will again force the IAF to get them with the US systems installed, probably in the hope that the IAF will deem it too expensive to rip out the originals and install the custom ones.

[save]

To avoid being targeted in a Tank you have both IR defeating systems.and also chaff-like dispensers making radar lock almost impossible.
The anti IR systems are quite new.

http://defensetech.org/2011/09/06/bae-developing-ir-cloaking-device/
http://www.bbc.co.uk/news/technology-14788009

To be able to knock them out in the future, you need better optical recognition systems, or better radar.

[fbEagle]

3 words. HOME ON JAM. ECM not all that its cracked up to be really

[bozon]

3 words. HOME ON JAM.

4 words. What does that mean?

[artik]

4 words. What does that mean?

Missile that is homing on ECM Radiation... but I assume it works mostly on stupid ECM.

ECM is only as good as the knowledge of the threat it is designed to defeat.

Probably the hardest point about it is that most of the data about ECM and radars is highly classified. On the other hand the physics is well known...

So I'm not 100% sure about that statement - finally radar has very well known properties and physics - there maybe some algorithms that try to filter ECM signals. We would probably never know what kind of threats can and cannot be defeated until the real life applications.

[artik]

3 words. HOME ON JAM. ECM not all that its cracked up to be really

One important point: Jamming (i.e. creating lots of noise on the relevant frequencies so the signal is get lost) is one of the types of ECM - usually most primitive one. Modern ECM jeopardises the radars by creating false signals or interfering with the original returned signal such that the missile or radar become fooled rather than disabled 

[GScholz]

Advanced ECM can fool the radar range, but not the bearing or elevation. Advanced fighter ECM only break STT track on radars that are targeting them, and even then they can deal with a limited number of radars at the same time (which is why they wouldn't be jamming radars in search mode). Bearing/elevation is all a missile needs to track.

From the AIM-120 AMRAAM Operations Guide:

"If at any point during the missile's time-of-flight the target starts to use electronic counter-measures (ECM) the AIM-120B can switch its tracking mode to home-on-jam. When this occurs the AIM-120B homes in on the location of the jamming signal, guiding it to the point where the onboard radar 'burns through' the jamming and re-acquires the radar. When in the home-on-jam mode the AIM-120B interlaces the active pulses of the radar with passive guidance from the home-on-jam equipment."

All the modern Russian BVR missiles also have this capability (and French, British, Chinese etc...)

[artik]

Advanced ECM can fool the radar range, but not the bearing or elevation. Advanced fighter ECM only break STT track on radars that are targeting them, and even then they can deal with a limited number of radars at the same time (which is why they wouldn't be jamming radars in search mode). Bearing/elevation is all a missile needs to track.

Not exactly and I'll explain why.

1. The angular resolution of a radar is quite low - especially of small radars that can only have very few elements in the planar array.
2. The signal that is sent and received by the radar comes from many directions (however with different strength)



3. The signal that radar receives is proportional to 1/r^4 while the signal recorded by the ECM is 1/r^2

Now consider the radar shoots a pulse while scanning to a slightly different direction, ECM can intercept that signal and send (stronger signal) with an appropriate timing - such that even an antenna that looks onto an entire different location would receive a signal that can spoof it, giving it false direction and false speed.

That what modern DRFM systems do.

If at any point during the missile's time-of-flight the target starts to use electronic counter-measures (ECM) the AIM-120B can switch its tracking mode to home-on-jam

There is a difference between Jamming and Spoofing.

Jam - is brute force lets send a strong signal that makes SNR so low that you can't determinate what is the signal - now I can go to the direction of the noise.

Spoofing is creating smart false signals - much harder - but when works much more efficient.

[GScholz]

That is true for small phased array radars, however you'd need very detailed information on the radar to fool it.

[artik]

That is true for small phased array radars, however you'd need very detailed information on the radar to fool it.

For example like a radar of AMRAAM, R-77 or (name other radar missile there) and so on. 

But it is also known to work well on much bigger and stronger radars...

It isn't only about it size. The DRFM is much more complex than just "jamming"

[GScholz]

Nope, they have more conventionally gimballed pulse-doppler radars.

[artik]

Nope, they have more conventionally gimballed pulse-doppler radars.

It looks like a simple small planar array radar  - which is even simpler