|Last Updated: Fri Mar 29 10:48:39 UTC 2013|
Breaking the Kill Chain
Air Power Australia - Australia's Independent Defence Think Tank
Air Power Australia NOTAM
27th January, 2009
Su-35 demonstrator #709 displays a mix of R-27 Alamo and R-77 Adder BVR missiles (KnAAPO).
Air combat relies almost completely on the effectiveness of missiles. Yet for a missile to down an aircraft there must be an unbroken ‘kill-chain’ of events terminating in the explosion of a warhead in close proximity to a vital part of the target aircraft.
Some people believe that missiles have near perfect chance of killing a target. While modern missiles are technological marvels of modern warfare, they have faults and weaknesses, not the least being critical phases of the kill-chain.
The mathematics is quite simple. Sort the kill-chain into a sequence of events, starting with the missile on its launch rail and ending with its warhead exploding. Assign a ‘Likelihood of failure’ at each step. Then take the previous link in the kill-chain’s Hit Probability, subtract the Likelihood of Failure from one, and multiply.
analysis is perhaps best illustrated by the
potentially lethal game of ‘Russian Roulette’ where one round is loaded
six-shot revolver, the cylinder is spun to stop at a random chamber,
is placed against the forehead and the trigger pulled.
The following is the player’s chance of
survival after a series of plays:
is may seem to be intuitively obvious to some –
a player will be certain to die after 6 turns of Russian Roulette - is
untrue. Even after twelve plays
where each chamber has a chance of being selected twice, and taking
account a 5% unreliability of the weapon, the player still has a 12%
Developmental AIM-120A round destroys a QF-102 drone (U.S. Air Force photo)
Air Combat Kill Chains
air combat is a high-tech, high-competency,
deadly business. Each side tries
to maximise the performance, reliability and survivability of each step
kill-chain, while maximising their own ability to disrupt one or more
the enemy’s kill-chain. These
actions take place simultaneously, at high speed and at times under
stress, so it is often a case of ‘the survival of the fastest and the
Breaking a Beyond-Visual-Range Kill Chain
The following describes a typical kill-chain, and how an enemy might seek to disrupt it. After reading the steps in the chain, assign representative values to the Kill-Chain Analyst model at the end of the NOTAM to make an overall assessment of the reliability of a BVR missile.
Active Missile Confirmed on Launch Rail. The pre-flight check shows an active missile on the launch rail. Or is it? Has an inert round been loaded by mistake, or has the round sabotaged on the way to the flight-line?
Search and Track Radar Jammed. Electronic Counter Measures (ECM) are designed to prevent the enemy’s radar finding, ‘locking’ and tracking an aircraft. Modern air-intercept radars are ‘jam resistant’ but not ‘jam-proof’.
Launch or Missile Failure. Missiles are often carried for several sorties before being fired or returned to a maintenance depot for test and refurbishment. Air combat places a high stress on missiles, especially in harsh climates. As an example, in Vietnam the Pk (kill probability) of the AIM-7E was less than 10%, with low reliability being one of the largest sources of poor performance.
Guidance Uplink Jammed. Jamming the missile guidance uplink is not considered very effective, as such links are directional and the missile antenna is usually pointed away from the target. In future warfare where aircraft are spread out and Network Enhancements are in place, it may be possible to a ‘buddy’ looking across a launch to disrupt the missile guidance by jamming it with AESA radar or a high-power microwave device.
Seeker Head Jammed or Diverted. This way of disrupting a kill-chain has a higher chance of success, as the missile’s radar small radar seeker requires high sensitivity to produce acceptable autonomous operational ranges. Digital Radio Frequency Memory jammers record and replay the missiles emission – but in a way designed to deceive the missile into computing a false location of its target. Flankers often carry the KNIRTI L005-S Sorbtsya wingtip jammer pods. In more advanced jammers, this configuration is capable of generating ‘cross-eye’ jamming which introduces an angular error into the missile seeker.
Chaff or Decoys Seduce Seeker. Generally, chaff is considered ineffective against modern missiles, is the internal signal Doppler processing discriminates chaff returns once they stop moving. What if the chaff moves at about the same rate as the aircraft? Forward firing, slow burn rockets or perhaps a modified round fired from the targets gun (e.g. the GSH-310 30 mm,) could draw a missile away.
Seeker Chooses Towed Decoy. Towed decoys work. If they did not, why fit them to vulnerable aircraft like the F/A-18E/F Super Hornet? Flankers may use a KEDR towed decoy. Used in conjunction with a Missile Approach Warning System (MAWS) the pilot can present the towed decoys to the missile before it reaches the aircraft – e.g. about 140 degrees off the nose. With DRFM replays of the missile seeker head emitted pulses, decoys can be very effective at making the missile track away from the aircraft, disrupting the kill-chain.
Aircraft Out-Manoeuvres Missile. Why fit a MAWS to a fighter aircraft? Is it to give the pilot a chance to mutter a quick prayer or curse before dying, or to provide a chance to ‘duck’ the incoming missile? The physics are that G-Forces in a ‘tracking’ turn of a given radius are a square of the speed. A typical engagement has the fighter doing Mach 0.9 and the Missile is arriving at Mach 3.6 - four times as fast as the fighter. If the fighter can generate a 5 G turn, the missile must track at 16 times the G to follow the aircraft, an 80 G turn. BVR missiles generally max-out at about 40G, so depending on the aspect, cannot track, so fly past the aircraft and miss.
Warhead Failure. Even at
the end of a long kill-chain, the warhead must fuze
and explode close enough its target to kill or inflict serious damage. Here is another opportunity for failure
or hostile jamming.
Su-35 demonstrator displaying the R-172/AAM-L, the R-27ET1 Alamo and the R-77 Adder at MAKS 2007 (KnAAPO).
So, putting all the steps together in the ‘Kill-Chain Analyst’ model, and providing reasonable estimates for the likelihood of disrupting each step in a modern engagement, this is the result – less than a 20% kill probability, or put another way, four out of five missiles fired will miss.
Is this a reasonable result?
done elsewhere have shown that the history
of the AIM-120 in BVR engagements has been 6 kills from 13 shots, a
probability of 46%. However, the
targets were ‘straight and level,’ un-alerted aircraft, not fitted with
electronic counter measures. One
was a helicopter. So, for
modern warfare when the enemy is network enabled, fully cognisant of
tactical situation, and takes every opportunity to break the
sub-20% kill probability for BVR missiles is likely to be the new
The latest generation of Western WVR missiles employ Focal Plane Array seekers with target recognition capability and high resistance to infrared countermeasures. Depicted imagery from the seeker of a Raytheon AIM-9X missile, which uses an Indium Antimonide bandgap detector array. Russian industry is working on such an FPA seeker, what is unclear is whether it will employ bandgap detector or superior two colour QWIP technology. When it enters production it is likely to become a block upgrade and new production item for BVR missiles such as the R-27ET and R-77T.
Breaking a Within-Visual-Range Kill Chain
In recent times, some people have had such (over)confidence in their BVR weapons, they have not paid much attention to within-visual-range contests. The exception is those unfortunate to be trapped in ‘Low Density / High Demand’ craft that don’t have the ability to escape from a fighter – transports, tankers and airborne early warning aircraft or other Intelligence Surveillance Reconnaissance aircraft. Some of these make a half-hearted attempt at self-defence by fitting flares and chaff dispensers, and Directed Infra-Red Counter Measures (DIRCM) systems.
As with the WVR case, read the steps in the chain, assign representative values to the Kill-Chain Analyst model at the end of the NOTAM to make an overall assessment of the reliability of a WVR missile.
Active Missile Confirmed on Launch Rail. As before, is this a real round or a dud?
Launch or Missile Failure. Failures are possible as with BVR missiles, but WVR missiles tend to be designed for higher G loadings and have fewer parts to fail, so expect the launch reliability to be higher.
Directional Infrared Countermeasures Effective. DIRCM is rarely fitted to fighters, so if none is present, the effectiveness is set to zero.
Seeker Head Jammed or Diverted. Older Infra-Red missiles like the early Sidewinders used a simple tracking device that could be diverted by a frequency-modulated signal – the head would slew away and break track. No such luck with modern, imaging seekers, where internal digital signal processing detects and disregards such measures.
Flares or Decoys Seduce Seeker. Generally, simple flares are considered ineffective against modern missiles. What of the future? Moving flares and decoys might have a chance, except an imaging seeker head will be looking for a large object, and will reject point sources. Two colour seekers will look at the blackbody characteristics of the infrared targets and since flares are hotter than tailpipes, reject them.
Chooses Towed Decoy. While
there have been plans to include infra-red emitters in a towed decoy,
could be defeated by an imaging seeker.
Aircraft Out-Manoeuvres Missile. ‘Dogfight’ WVR missiles have been designed to fly close, high-G ‘knife fights’. They have turning capabilities of about 80G and have attack profiles that reduce closing speeds making it possible to track a high-G target. Generally, it will be rare for a fighter to ‘duck’ an incoming WVR missile.
Warhead Failure. Reliability is still an issue, but the smaller
size of the
also means the warhead is smaller. Large
aircraft like the Flankers have armour-like
structures around the
engines, which are widely spaced, so a hit might damage, but fail to
type of aircraft.
This is a result that looks a lot more like the Manufacturer’s brochure and promises. Apart from the reduction of kill probability arising from the size of the warhead, the WVR kill-chain has fewer links and less areas of vulnerability to attack, so a WVR missile launched within its engagement envelope may well kill at this rate.
result matches the record of AIM-9L firings in
the Falklands conflict where 26 missiles
were fired for 19 kills – a Pk of 73%.
Those LD/HD aircraft that fit a DIRCM effective about 50% of the time will still have to endure a kill-probability of about 40% per missile. And if the missiles miss, there are still guns to shred large, slow and soft aluminium structures.
Su-30MK launching an R-77 (KnAAPO)
The Bottom Line
Most fighter pilots rightfully fear a merge followed by a knife fight where WVR missiles are loose. These missiles may be unable to discriminate between friend and foe, and like a rabid dog, will attack the nearest target they find. ‘Mutually Assured Destruction’ (MAD) is possible, as the engagement ranges of WVR missiles are often about the same, so each side might fire a missile and down the opposition.
An inconvenient though inevitable and accurate assessment of this analysis would be that as BVR missiles lose kill probability because of disruption of the kill chain, merges and WVR engagements are more likely, with higher losses all-round.
If future air combat, those with the most BVR rounds, the ability to egress a fight before a merge, and flying tough, multi-engine aircraft that can take a WVR missile hit and still get home, will be the winners.
F/A-18E/F Super Hornet vs. Sukhoi Flanker Analysis [Click for more ...]
Sukhoi Flanker Analysis [Click for more ...]
F-22A Raptor Analysis [Click for more ...]
Joint Strike Fighter Analysis [Click for more ...]
Power Australia Website - http://www.ausairpower.net/
Air Power Australia Research and Analysis - http://www.ausairpower.net/research.html
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