Modern Heat-Seeking Air-to-Air Missiles

[shehbazi2001]

While this topic is complex and lengthy, I have just tried to present some basics only. Purpose is just to initiate a healthy discussion on the topic and learn from one another.

Using easy examples, there are two types of heat-seeking missiles. One that "smell" or "feel" the aircraft and others that "see" an aircraft. The former are ordinary IR seeker missiles and latter are Imaging Infra Red seeker missiles.

Imaging IR seekers are those that actually "see" the thermal image of the aircraft. For early heat-seekers, aircraft was a dot in the sky. The Imaging Infra Red seekers are identified by their transparent glass domes at the nose. AIM-9X, ASRAAM, IRIS-T, MICA-IR all have transparent glass seekers.

The ideal seeker would be a dual-band Imaging Infra-Red seeker. It needs to be verified, but MICA seems to be doing it.

The seeker of FIM-92B Stinger MANPADS (Man Portable Air Defence System) used a dual-band seeker using both Infra-Red and Ultra-Violet bands, almost 30 years ago. FIM-92C was a reprogrammable microprocessor equipped (software) Stinger.

As the flares are mostly in Infra-Red spectrum, they are useless against a seeker who also seeks ultra-violet radiation. Block-II Advanced Stinger uses an Imaging Infra-red seeker.

Almost all the Imaging IR seekers use image-processing techniques and thus microprocessors and thus software for it. Getting this software is extremely important. As the imaging seeker sees the whole aircraft, it can be programed to hit the hottest engine part or less hotter fuselage, according to the tactics developed by the air force.

All missiles have impact fuses and now its important to see what other fuses are installed. For air to air, the proximity fuse is most important after the impact fuse because either the missile shall hit the target or it shall miss it by a small margin. Therefore its necessary to initiate the warhead on hitting the target and when its nearly missing the target. Fuse is the thing that explodes the warhead.

AIM-9L Lima has laser-proximity fuse, which is jam resistant. ASRAAM also uses laser proximity fuse, which is plus point. MICA uses RF (radio frequency) proximity fuse, which "seems" a disadvantage to me. However, PAF can demand to install a laser-proximity fuse from the manufacturer as it should not be difficult.

Lock-On After Launch (LOAL) is important for those fighters that carry missiles internally like F-22 or F-35. The seeker of missile is not out in the air to feel the heat or IR radiation. LOAL is useful also for submarines carrying such missiles.

Also LOAL is required for backward firing of missiles ie firing it straight and then the missile turns 180 degree to the rear and achieves a lock upon seeing the target. I dont know if PAF is interested in LOAL capability.

Warhead of MICA seems to be the most advanced one, using "Focused Splinters". When an ordinary warhead explodes, it distributes its explosive energy (destructive power or blast power) equally in all directions. This is not desired. We want the explosive energy to be directed towards the target.

MICA's warhead seems to be doing it. If MICA misses the target by a little margin to the right side, the proximity fuse shall initiate the warhead and warhead shall explode, sending its splinters towards the aircraft (left side of the missile). This is directed-energy warhead technology. I think this was first used in anti-tank missiles, with top-attack anti-armour warheads. The warhead concentrates most of its energy in direct downward direction to damage the tank or other armoured vehicle to the maximum, without diving on it.

Thrust-Vector Control (TVC) is another feature of the new missiles. ASRAAM, Python-4 and Python-5 are not using TVC. Pythons use complex aerodynamic controls for achieving good turn rates but ASRAAM is neither using complex aerodynamic surfaces nor TVC, casting doubts on its maneuverability (turning performance). MICA, IRIS-T, R-73 use TVC.

IRIS-T is said to pull 60g and MICA 50g and Python-4 is siad to pull 70g. But I
think that the measure of turning performance (both aircraft and missiles) is not so simple. Its not just pulling so much gs. Minimum turn radius is also not sufficient.

Important thing is time, tightest turn in shortest time is what we need to look. If an aircraft or missile makes a more tight turn but takes longer than his opponent, who pulls a less tight turn more quickly, then there is no use of this tightest turn. Tighest and fastest turn is what is required. Thats why we talk of corner speed, the speed at which turning performance is maximum.

Now comes the solid rocket motor. In early missiles, the rocket motor burn times were short and the missile would fly unpowered towards its target at max range and become energy-less, easy to dodge. Now the energy of rocket-motor is better managed to give it more energy at "end game". This is achieved through dual-thrust rocket motors, meaning that thrust of rocket is not the same during the flight, the thrust is increased slowly as the missile nears the target and then drops off.

AIM-9B followed 1 micron radiation, which is the hottest zone of an aircraft. AIM-9L follows 4 micron radiation, which is not the hottest region of aircraft and is more the fuselage. The more hot an object, the smaller would be the radiation wavelength. The smaller the wavelength, the higher the frequency.

wavelengths of typical flares????? if the wavelengths of the current flares are near 4 microns.....they can possibly fool the incoming Lima.... Therefore the flare systems used by PAF aircraft must be tailored according to the seekers of the Indian or other threatening force's heat-seeking missiles. We also need to see what Mr Mike (AIM-9M) is upto, if PAF is getting it.

Still many things remain like arming of the warhead, navigation techniques used, ranges, minimum launch speed restrictions (all heat-seeking missiles cant be fired from helicopters because of minimum launch speed restrictions), further filters for ECCM, maximum speed and its effect, inter-operatability with Sidewinder rails, seeker cooling systems, range of Proximity Fuse and its effect??? etc etc.

Further discussion can be continued in the thread.

 

[Muradk]

Shehbazi:
Thrust-Vector Control (TVC) is another feature of the new missiles. ASRAAM, Python-4 and Python-5 are not using TVC. Pythons use complex aerodynamic controls for achieving good turn rates but ASRAAM is neither using complex aerodynamic surfaces nor TVC, casting doubts on its maneuverability (turning performance). MICA, IRIS-T, R-73 use TVC.

IRIS-T is said to pull 60g and MICA 50g and Python-4 is siad to pull 70g. But I
think that the measure of turning performance (both aircraft and missiles) is not so simple. Its not just pulling so much gs. Minimum turn radius is also not sufficient

Will they work against F-22's and F-35, they have a black out button , I think you know what I mean with such Gs would the missile get these 2 fighters, yes or no?.

 

[JK!]

Could you provide any info on the likes of MBDA meteor missile?

Apparantly its speed is mach 4+

 

[shehbazi2001]

Shehbazi:
Thrust-Vector Control (TVC) is another feature of the new missiles. ASRAAM, Python-4 and Python-5 are not using TVC. Pythons use complex aerodynamic controls for achieving good turn rates but ASRAAM is neither using complex aerodynamic surfaces nor TVC, casting doubts on its maneuverability (turning performance). MICA, IRIS-T, R-73 use TVC.

IRIS-T is said to pull 60g and MICA 50g and Python-4 is siad to pull 70g. But I
think that the measure of turning performance (both aircraft and missiles) is not so simple. Its not just pulling so much gs. Minimum turn radius is also not sufficient

Will they work against F-22's and F-35, they have a black out button , I think you know what I mean with such Gs would the missile get these 2 fighters, yes or no?.

Not easy and evident to answer for me for the moment. With a pilot, Aircrafts normally go upto 9g and occasionally a little bit more. But the new missile pull a lot of gs, upto 50-60. Now the question is genuine that how a man with a 9g limitation is going to compete with 50gs? I think there are chances still to survive. I dont remember exactly, but I read it in a book of the UK Publisher Brassey's Air Power series.

Gs are also related to speed alongwith turn radius. 9gs pulled at 1000 miles per hour will not give the same total turn as 9gs pulled at 500 miles per hour. Missiles are much faster. A missile at Mach-2 pulling 20 or 30g may be equal in terms of turn radius (but much faster) to a fighter at Mach-1 pulling 10g, for example.

With regard to F-22 or F-35, the newer missiles seem quite capable of handling them. But our topic is a delicate one, therefore, room for improvement will be there.

 

[Myth_buster_1]

very informative thread indeed..
dont for get A-Darter which i believe is the best ASRAAM for PAF needs... A-darter in cooperates a lot of features from British ASRAAM and Israeli Phyton 5 as well as it own unique feature of low-drag wingless airframe with TVC, thus ensuring highly maneuverable tight turn capability and with Lock-on after launch capability will give best kill result!

 

[blain2]

Shehbazi:
Thrust-Vector Control (TVC) is another feature of the new missiles. ASRAAM, Python-4 and Python-5 are not using TVC. Pythons use complex aerodynamic controls for achieving good turn rates but ASRAAM is neither using complex aerodynamic surfaces nor TVC, casting doubts on its maneuverability (turning performance). MICA, IRIS-T, R-73 use TVC.

IRIS-T is said to pull 60g and MICA 50g and Python-4 is siad to pull 70g. But I
think that the measure of turning performance (both aircraft and missiles) is not so simple. Its not just pulling so much gs. Minimum turn radius is also not sufficient

Will they work against F-22's and F-35, they have a black out button , I think you know what I mean with such Gs would the missile get these 2 fighters, yes or no?.

I think yes. The idea behind F-22's air dominance is as such where it would typically not get involved in a close knife fight having taken out the adversary at BVR. I think the 5th Gen WVRAAMs in close in combat are dangerous for 4th and 5th gen platforms alike.

At least one F-16 shot down a F-22 in WVR combat with the simulated AIM-9x shot.

 

[shehbazi2001]

Could you provide any info on the likes of MBDA meteor missile?

Apparantly its speed is mach 4+

Infact the Meteor is not a heat-seeking missile and is rather long-range BVR, therefore it was not included in this discussion. May be some other time.

 

[JK!]

Infact the Meteor is not a heat-seeking missile and is rather long-range BVR, therefore it was not included in this discussion. May be some other time.

I look forward to it.

Regarding ASRAAM it only has a set of guidance fins on the rear and non at the front like say a sidewinder.

How does that affect overall control I mean for better or worse?

 

[shehbazi2001]

I look forward to it.

Regarding ASRAAM it only has a set of guidance fins on the rear and non at the front like say a sidewinder.

How does that affect overall control I mean for better or worse?

Apparently, USA and Germany separated from ASRAAM due to its lack of Thrust Vector Control and thus maneuverability. US went for AIM-9X and Germany went for IRIS-T. But interestingly, I read that AIM-9X and ASRAAM share the same Imaging Infra Red seeker.

But it does not necessarily mean that ASRAAM is inferior. The design philosophy of ASRAAM is different than others. It may not need to turn very hard like others. Usually the missiles follow intercept courses and dont strictly chase the aircraft.

At the same time, I think that ASRAAM shall not be able to take a backward or even 80-90 degree aspect shots like Pythons or TVC equipped missiles. So even if its not inferior in most traditional shots, there are some areas where it cant compete with others.

 

[shehbazi2001]

A factor that affects the performance of heat-seeking or IR missiles is atmospheric elements like Clouds, fog, mist, sandstorms etc.....and this effect must be seen before acquiring a new short range Air to Air missile....

Mist, clouds and rain mask heat signatures and so prevent effective use of infra red guidance. Earlier models of Sidewinder could easily be fooled by the Sun, clouds, flares, or even rain.

The atmosphere basically affects IR energy in three different ways - absorption, scattering and scintillation. Missile is said to lose "sight" of the target....clouds absorb and scatter the IR radiation and some a bit less important like sandstorms too scatter the IR radiation. Sandstorms may become important over Rajihstan area of Sindh and clouds/Mist is a special consideration over all of Pakistan especially in Winter.

If the water vapour concentration increases, scattering becomes noticeable. Scattering occurs when the wavelength of the IR is comparable in size with the scattering particles. Clouds and fog contain droplets around 1 micrometre in size - this results in extremely low transmission throughout most of the IR band.

On the other hand, rain droplets are much larger, with the seemingly surprising result that IR transmission through rain is substantially better. Rain is liable to degrade the systems performance, but still allow it to function.(From Aust Air Power)

It is claimed that ASRAAM counters the target obscurity in clouds....given the weather over UK and Europe, this seems to be an advantage...

Heat seeking missiles cant be true all-weather weapons.….and although the later Sidewinder models are good as compared to earlier……it seems true that if an intruder gets into cloud cover, the range of Sidewinder shall decrease…..

For a stronger response to an intruder and to make sure he is shot down, we need both the newer generation heat seeking missiles and radar-equipped BVR missiles onboard our fighter aircraft…..

For AIM-9L and R-73 specifically, it would be interesting to know that exactly how much the acquisition range is affected by a specific type of clouds......

 

[fatman17]

^^^pls check out the following post in WMD and Missiles section called "back on course - air launched weapons" - this was posted a few weeks back but surprisingly there were no responses.!

 

[shehbazi2001]

Normally we consider the horizontal range of a missile alongwith its off-boresight angle engagement capability but one other crucial parameter is the difference in altitude of two aircrafts.................Aspect is no more discussed because all-aspect capability is now common............

This is an important aspect of these heat-seeking short-range missiles that is mostly overlooked...

In other words, we should consider that upto how much altitude difference can it get a lock? It all about the launch envelope..................

Normally we do mention it for radar-guided BVR AAMs but mostly it is not mentioned for IR- or IIR-guided WVR missiles like AIM-9L/M Sidewinder, R-73, Magic-2, ASRAAM, Python-4/5 etc......

From a comparison we can see that which one of them can get a lock on more high or more low-altitude target.............

For the early heat-seekers, we know that the launching aircraft had to be in at the tail of target (aspect) and almost at the same altitude as target with almost no off-boresight angle..............

So can we shed some further light on the details of missile's ability to engage targets with difference of altitude and how much difference for various systems? An important parameter for comparing different systems..............

 

[shehbazi2001]

Continuing on the last post of the thread about IR missile capability with respect to altitude gap.......

Importance of Line-of-Sight Range for Air-to-Air Missiles

As discussed earlier in the thread, whenever short-range IR missiles are discussed, mostly horizontal ranges with head-on and tail-on configurations are mentioned. Sometimes the effects of launch altitude and launch speed on missile range and maneuvering capacity are also mentioned. But what normally lacks is the ability of missiles to engage targets with a large difference in altitude.

Lets say that the tail-on range of a Sidewinder is 10 miles. Its evident that this 10 miles is not a vertical range because a Sidewinder can't be expected to kill or lock onto a target which is 10 miles high either due to the missile seeker's inability to acquire target at such altitude or because the rocket motor burns out quickly in such a climb.

While it is true that with large altitude difference, mostly radar-guided BVR missiles are used, still for a surprise kill, IR missiles can be employed. It can also happen that radar-guided BVR missiles are used up.

One possibility of surprise interception is that IR missile be launched without radar lock with range estimated from air-to-air laser range finder / IRST/ AWACS input etc. For such a surprise shot, it is important to know the engagement envelope of one's missile especially the vertical range from low altitude upwards and inversely. As a Stinger MANPADS can engage targets upto a maximum theoretical altitude of 11,000 feet, it can be guessed that IR-missiles without Lock-On-After-Launch feature can't engage target if altitude difference is around 15-20,000 feet. If you have precise figures, please post it.

Lets consider a scenario. An aircraft is flying at 30,000 feet altitude and is one mile behind a target which is flying at 100 feet. Can this aircraft fire AIM-9L/R-60/R-73/Magic-2/R-27T on target from that altitude without diving for it? Perhaps Not. The other question is whether low-flying aircraft at 100 feet can engage the high-flying aircraft at 30,000 feet with above IR missiles? seems negative.

For a downwards shot, the rocket motor range may not be a problem but the seeker still may not acquire the target due to large altitude difference. For an upwards shot, the rocket motor range will also be important in addition to the acquistion range of seeker itself.

IAF is planning to arm Jaguars with ASRAAM because Jaguars do low-level flying and need a missile that can engage high flying fighters. Lock-On-After-Launch (LOAL) feature enables ASRAAM to climb towards target without lock-on until target is within the seeker range.

In 1980s, IAF acquired Mirage-2000s for deep penetration strikes at low-level because they were armed with Super 530D which could engage targets with a large altitude difference. But as Jaguar-IS and Mig-27 do not carry nose radars, they needed an IR missile with good vertical range.

Modern air to air IR missiles featuring LOAL are ASRAAM, AIM-9X, IRIS-T, Python 5 and MICA-IR. The baseline R-73 used by IAF is a good dogfight missile but reportedly lacks LOAL feature.