This is what the F-22 can do

[Weta43]

Personally - I don't think IRST is a miraculous answer to the F-22, nor do I think it will ever take over from radar. Radar has many advantages over optical systems, not least of which is it’s all weather capability.

I do think that the F-22 & other 'stealthy' aircraft will cause an 'arms race' amongst the designers of radars & other sensors that will decrease the effectiveness of that technology (at least of the generation presently coming into use)

I also think that (despite GG's belief that optics are of no relevance) optical sensor research (which of necessity include optics) will also be fed money & improvements will be made, in the same way that radar has improved in response to the demands made of it.

Modern computers are now powerful enough to allow active adaptive optical systems that use laser beams projected along the view path to determine how to correct for turbulence & thermal variations in real time. This means that the distance at which a relatively small object can be seen is increased exponentially. (The point behind mentioning the satellite imaging was purely to point out that optical systems are already capable of resolving very small objects at well beyond visual ranges - not just stellar objects at astrological distances.)

Couple such an optical system to a properly cooled IR sensor & processing system & you have a device that will search for & find BVR exhaust heat & panels heated by friction. Cuing the system with information about where to look with an EWR system would increase its effectiveness – as it presently does radar’s.

Fitting such a system into a missile would be impractical given the present state of the technology. Fitting it to a plane would be a lot less of a problem (the advanced system would be on the plane, not the missile GG, just as you don’t a fit full BVR search radar to the AIM-120).

If the IRST system can be upgraded to the point where it can scan, detect & track BVR then there the obvious next step would be to build BVR IR missiles receiving mid course correction from the plane carrying the advanced optics & have the terminal homing taken over by a conventional type – or more advanced - IR seeker (maybe like an R-27ET WITH mid course correction :-)

The principle of the IRST doesn’t limit it to WVR ranges, only the present level of development of the systems does. Better optics & a more powerful laser mean better detection ranges and better tracking ranges – well into BVR ranges. You then have a device that will track a ‘stealthy’ plane like the F-22. At least on a sunny day…

[GGTharos]

MICA IR has MCU's. :)

 

But I think you are oversimplifying the issue; sattelites have it relatively easy. They're very stable, they don't need a high-power gimbal, and they don't have to worry -too- much about a lot of self-noise sources that aircraft-mounted IRSTs do.

 

To give you an idea here, missiles can -already- sense heated up panels from friction, but their head on range is still pretty crummy!

 

Contrast -seriously- fades with distance .. imaging IR helps, but lack of zoom will basically nullify this for BVR. Existing IRST's -already- 'do it like the radar' but they can't take advantage of all the processing techniques a radar can use.

[Pilotasso]

Personally - I don't think IRST is a miraculous answer to the F-22, nor do I think it will ever take over from radar. Radar has many advantages over optical systems, not least of which is it’s all weather capability.

I do think that the F-22 & other 'stealthy' aircraft will cause an 'arms race' amongst the designers of radars & other sensors that will decrease the effectiveness of that technology (at least of the generation presently coming into use)

I also think that (despite GG's belief that optics are of no relevance) optical sensor research (which of necessity include optics) will also be fed money & improvements will be made, in the same way that radar has improved in response to the demands made of it.

Modern computers are now powerful enough to allow active adaptive optical systems that use laser beams projected along the view path to determine how to correct for turbulence & thermal variations in real time. This means that the distance at which a relatively small object can be seen is increased exponentially. (The point behind mentioning the satellite imaging was purely to point out that optical systems are already capable of resolving very small objects at well beyond visual ranges - not just stellar objects at astrological distances.)

Couple such an optical system to a properly cooled IR sensor & processing system & you have a device that will search for & find BVR exhaust heat & panels heated by friction. Cuing the system with information about where to look with an EWR system would increase its effectiveness – as it presently does radar’s.

Fitting such a system into a missile would be impractical given the present state of the technology. Fitting it to a plane would be a lot less of a problem (the advanced system would be on the plane, not the missile GG, just as you don’t a fit full BVR search radar to the AIM-120).

If the IRST system can be upgraded to the point where it can scan, detect & track BVR then there the obvious next step would be to build BVR IR missiles receiving mid course correction from the plane carrying the advanced optics & have the terminal homing taken over by a conventional type – or more advanced - IR seeker (maybe like an R-27ET WITH mid course correction :-)

The principle of the IRST doesn’t limit it to WVR ranges, only the present level of development of the systems does. Better optics & a more powerful laser mean better detection ranges and better tracking ranges – well into BVR ranges. You then have a device that will track a ‘stealthy’ plane like the F-22. At least on a sunny day…

 

The laser distortion compensation as you describe here is aplied to the Boeing 747 ABL. Its a complex system and requires stable flight and absolutely stable weather, wich is only true above the stratosphere, and then the system takes several seconds to find an optimal flexible lens config.

And BTW its too big to be mounted on fighters.

 

The technology that may defeat stealth is theorized on paper but current electronics give it a ludricoulsy low range, at wich conventional radars could burn through anyway.

[Weta43]

It’s 02:50 here & I’m getting a bit dopey, but -

Satellites do have it easy - I only mention them to show to doubters that seeing something the size of a plane – or a cigarette packet if you like - from 160 km is easy if you've got the gear & know where to look (which by definition means being able to use it's contrast against its surroundings to find the object).

Missiles can- as you said – already detect panels heated by friction – not particularly well, but that is with sensors tightly constrained by the need to fit in the guidance portion of a missile. The light gathering devices on missiles are relatively small & the area of the lens available to gather light has a direct bearing on the ability of a device to pick up faint sources of light – you don’t shoot sports photography, look at the stars or find planes 100km away with a lens that’s 3 inches in diameter, & remember – double the size of the ‘lens’ , (quadruple the amount of light you gather & because radiation dissipates at the inverse square of the distance) double the range at which a radiating object of the same brightness can be detected. You can increase the size of the optics on a plane – you can’t do it on a missile.

Optical devices can’t take advantage of all the processing that modern radars can – but processing of signals from optical devices is improving quickly. Computers now allow the use of data from a number of smaller devices to be combined to give the effects of a virtual device with a collector equivalent to the combined size of all the individual collectors.

You might argue that turbulence & thermal variations in the atmosphere mean that you can’t say ‘double the size of the optics, double the distance you can detect an emitter’ - which is all we’re after initially – find the plane from its radiated energy, (then you have a bearing and you know where to point the lidar) but active adaptive optics have pretty much already overcome that as an issue & also allow your lidar to do the range finding over BVR distances.

I’m not sure why you suggest there would be no zoom for BVR on a system mounted in a plane…

Technology already exists to isolate a system from the vibrations of a plane & the gimbals only need to move a mirror, not the whole system.

Blah Blah Blah,

Better do some work :-)

[Weta43]

I know this wasn't what you were getting at Pilotasso, but what you're actually saying is that there is an actual working, flying prototype of the system in operation now that only needs development. ('And BTW its too big to be mounted on fighters.' - like early computers were)

Optics are unlikely to supplant RADAR in the near future & probably never on a rainy day, but the technology - as you said - exists to bring optical detection, range & tracking to BVR distances. It just needs developing.

Historically there hasn't been huge pressure to develop IRST systems BVR because radar has been so effective in this realm, but increasing stealth technology is reducing the effectiveness of radar & improving optical detection is an obvious supplement to radar – one perhaps with better detection ranges under ideal conditions.

 

edit - you say:'which is only true above the stratosphere' but the systems were actually developed to allow astronomical telescopes to look up through & compensate for, the entire atmosphere - from the ground on up...

[GGTharos]

No, you've got me all wrong. You can double optics -all- you want ... but your sensor needs resolution. No zoom, no target at long ranges, as it will subtend an arc lesser than a pixel.

 

And wether you like it or not, all this isolation from vibrations only helps so much.

 

For this reason, IR systems will remain a non-BVR sensors well into the forseeable future against any but the hottest of targets, or tail-on targets.

 

In addition the wavelength is important, and contributes to detection range.

[Weta43]

Ok - clarification –

I was taking a high level of magnification as a given. Why I mention optic size is this:

Say a heated object radiates energy at a certain level.

At a particular distance (far enough to consider it radiating like a point source) this energy falls at some number of watts per square meter.

At double the distance the energy falls at quarter that intensity.

If you use a sensor that has a particular sensitivity – needs more than a specific amount of energy to fall on it to fire - & at some distance a lens of 10cm radius with a particular magnification just gathers enough light to form an image of the emitter with that threshold level of energy intensity, at 2 times the distance the image will only have ¼ the energy intensity needed to fire the sensor.

Similarly, if the lens is capable of actually resolving an image larger than the individual pixels, not just a point smaller than the pixels, and the diameter was unchanged, but the focal length was changed to give twice the magnification, the image will only have ¼ the energy intensity needed to fire the sensor.

But –if you double the radius of the lens, in both cases the image remains bright enough for the sensor to register it. That’s why lens size is as important as zoom - & I know you already know this – that’s why astronomical telescopes are made with huge lenses or mirrors, not just powerful magnification. To increase the amount of light they gather & increase the image brightness above a detectable threshold.

You can increase the magnification all you like on a IRST system (or seeker), but if you don’t increase the size of the optics the image gets so weak that the target can’t be detected (presumably what you meant about reduced contrast). Increasing the size of the optics brightens the image (increases contrast) & overcomes this problem.

 

Edit - the image created by the lens can be smaller than a single pixel & still register, as long as more energy falls on that pixel than is needed to make it fire. If you double the zoom & the new image is still smaller than the pixel then the same amount of energy is falling on the pixel & it still fires, but is still only a 1 pixel image.

[GGTharos]

I'm well aware of how optics, work yes.

 

THe other problem you face is that increase in lens size typically corresponds to an increase in focal length ... so you've got yet another dimention to deal with.

 

At some point, the device becomes too draggy and impractical.

 

And, again, you're right about increased light gathering, but these things are not telescopes - telescopes are delicate things that have significant -in-tolerance- to being mounted on anything resembling an aircraft, but then, their application is very different.

 

Basically your ability to spot something at 160km is going to be better with an actual telescope than an IR sensor or any kind (for now). I'm not going to buy this fantastic capability exists quite yet, or that it will exist any time soon.

 

There are a -lot- of issues to overcome when it comes to long range detection and tracking, such a weather, mechanical vibration, target contrast (which is in fact quite low typically - I know, I've looked through RL IIR optics) and significant clutter (it really doesn't matter which way you're looking at these distances. The clutter's there, be it a cloud or a star). There are -a lot- of sources of pollution to prevent this from working, at least until computers can 'see' and recognize things at least as well as we do, and much faster than we do ... while somehow negating mechanical vibration. (Note: We can go deeper into this one since there's some if-then's so what I said isn't really absolute)

 

It is -much- more likely that LIDAR will be utilized instead.

[nscode]

And wether you like it or not, all this isolation from vibrations only helps so much.

 

Vibration damping isn't so hard to solve actually... just look at how your CD drive does it and scale it up a bit :)

[Weta43]

Focal length & lens diameter are entirely unrelated GG. (hmm..That smells like a red herring :-) The focal length of my 28 - 200mm lens on my camera changes as you move the elements - not as you change the size of the lens.

Yes - At some point the device may become too large & aerodynamically draggy to be practical on a plane - though most fighters find room to carry a radar antenna almost the same diameter as the fuselage of the plane & some of those underbody pods would allow a pretty big lens system - but this is also why I mentioned that it is now possible to combine the signals from a number of smaller devices to sift the signal from the noise.

Any digital camera working at any part of the light spectrum IS a telescope of some description focusing light on a sensor array. Telescopes are as fragile as the most rugged camera. (any camera in space - spy satelite or Hubble telescope - went through 8G & a lot of vibration to get there)

The active adaptive optical systems you would need to find a fighter at 160km already exist - & are in use in planes - though as Pilotasso said they're airliners & the gear's still much too big & temperamental for fighters, & though they can deal with the vibrations they can't deal with major course corrections - yet :-), but like the GPS units made for trampers, the hard drive in the PalmOne Treo sitting on the desk here or the laser pointers in the $2 shop - they'll get smaller & more rugged.

Yep - LIDAR will be used. I suggested using emitted radiation - to get a bearing only - because it's passive & wouldn't alert the target, but the requirements of the optics are the same whether you rely on emitted radiation or a laserbeam for illumination. The processing to find the target in the image are easier if you scan with the laser though (look for a return at a specific frequency - not a whole lot of doppler shift on a laser beam).

[Crusty]

M.A.D. ?

[pho3nix]

All you guys have valid points, but to clear up some issues, IRST does not primaraly depend on image quality (adaptive optics) simply because you are just trying to detect the source, no image it (yet), also the discussion about irradience is correct, but as you all stated, larger diameter = higher angular resolution, this can be improved via 2 or more detectors placed at a distence and measured coherentley (phase) which can be easaly done via optical fibres. with this respect you could have x amount of gimbled detectors on you aircraft all linked together to provide the same irrediance with much higher angular detection.

 

Just think about it.

 

PS the detectors may only be the size of a AIM-9 head or so behind a indium-tin oxide window to preserve X-band conductivity

[Guest IguanaKing]

So...what does X-band have to do with IR? They are separated by thousands of millimeters of wavelength. Think you can train the average aircraft maintainer to deal with fiber optics in only a few months? Think again. This kind of stuff isn't used in combat aircraft because it is extremely sensitive to termination and splicing. This skill is more of an art than a science...well, actually its completely scientific, but not to the point where any average guy off the street can maintain it effectively. It takes YEARS of training and practice to get any good at it. One stray AAA round or piece of shrapnel from a SAM would render such a fiber-optics system useless for...well, probably the duration of most future wars. That is even ASSUMING you have qualified personnel to deal with it.

[Weta43]

The reason I mentioned adaptive optics is that if the source subtends a very small angle & is distorted by the atmosphere it's image will be blurred across several pixels & may not fire any of them. If the image can be sharpened up then all the reflected or emitted energy from the target collected by the lens will land on a smaller number of pixels ( maybe 1 ) & the chances of the image being detected go up.

[Weta43]

Iguanaking - I'm not talking about things that they're going to implement by Xmass here, just what I think could be the capabilities of a system if it integrated some existing technologies. If they develop the technology they'll have to make it serviceable & they'll have to train the technicians.

When they put the first gas turbine in a tank I bet most of the guys doing diesel maint went - 'no way' & said 'how will they maintain it' - but they do.

I don't know how to maintain or repair the radar absorbing material on the outside of an F-22, I'm guessing you don't either - but it's probably pretty specialised & needs the right gear - & presumably somebody on the bases they operate out of will know how to do it ...

[Guest IguanaKing]

Weta, even to an 18-year technician like me, L-band receivers are still black magic...even the relative angle of a component in the receiver or IF boards can make several dB difference with a change of mere seconds in angle. A fraction of an ohm in an L-band diplexer can mean the difference between a good transponder and one that fries its own receiver with its own transmitter emissions. Receiver circuitry and interconnections get even more complicated as the frequency goes up. Comparing this stuff to turbine engines is a bit of a fallacy, since a gas turbine is actually one of the simplest engines in existence...and it can run on just about any combustible liquid you supply it with. And yes...even American turbines can do this. BTW...gas turbines are not all that different from a diesel engine.

[Weta43]

But it's all black magic till you can do it. My guess is almost everything you do in your job was black magic till they trained you.

If the military (or industry for that matter) finds a need for a technology, they'll find a way to make it servicable & they'll train people to repair it - even if that means just swappin out pre-configured modules.

The point wasn't that gas turbines are complicated (I explained how they work to my 10 year old the other day), but that people without training on them (Joe deisel mechanic) probably find the idea of working on them mind boggling.

[Crusty]

Iguana....I understand your point abouthigh power rf circuits, but

I believe the internet has created a quite a few people skilled in fibre optics

if a bloomin bt engineer can produce a splice in the field it cant be that "magical" now can it?

[nscode]

A fraction of an ohm in an L-band diplexer can mean the difference between a good transponder and one that fries its own receiver with its own transmitter emissions.

 

That is a common thing for any tranciver device, only with freq the tolerance gets smaller.

 

And if you can train this bunch:

 

 

to maintain an F-16.... you can train just about anyone to do just about anything :lol:

[nscode]

There's nothing anty-american about my comment. These guys are a walking comedy show regardles of race and nationality :D

 

YOU are the one going offtopic here.

 

As for your insulting comments on PM, that's what the ignore list is for. So long..

[504 Wolverine]

What the hell is wrong with the Serbs on this board? Always trying to get a dig in on the Americans. This board is supposed to be for people who love flight sims and Lock On in particular. Frankly, I don't give a crap about your anger or distaste for the American military. Maybe you should post bullshit comments like that elsewhere. Neg rep inbound.

 

Why am I not suprised that you will send neg rep, afterall you and your fellow squadmate Bsr LOC use this very system to bully and harrass other people like little playground bullies when the teacher is not around cause you got the ok from wags statement that the rep system or PMs are not moderated. Well lovley job, you can insult and bully people but don't let us see it. The mods need to get the forum rules into perspective cause at the moment this stinks.

 

Personally I say remove the rep system or moderate it.

 

Also what do you expect the serbs on this board to do when people like you sit and prod them with a stick. You say the trouble is with people hating the yanks, I say its yanks like you and LOC posting troublesome posts, then when someone gets angered and replies to these post you start the old "your anti-american" bull.

[Crusty]

edit..wrote a boring post here disagreeing with ruggbut (so whats new)

decided it was pointless

[bSr.LCsta]

Why am I not suprised that you will send neg rep, afterall you and your fellow squadmate Bsr LOC use this very system to bully and harrass other people like little playground bullies when the teacher is not around cause you got the ok from wags statement that the rep system or PMs are not moderated. Well lovley job, you can insult and bully people but don't let us see it. The mods need to get the forum rules into perspective cause at the moment this stinks.

 

Personally I say remove the rep system or moderate it.

 

Also what do you expect the serbs on this board to do when people like you sit and prod them with a stick. You say the trouble is with people hating the yanks, I say its yanks like you and LOC posting troublesome posts, then when someone gets angered and replies to these post you start the old "your anti-american" bull.

Why don't you piss off, and mind your own bussiness. Your buddy Kenan (who at one point was kicked from your squad for saying stupid crap on these boards) gets neg rep because he says things that deserve it. The point of the rep system is to show your approval or disapproval of someones post. It's not my problem if he can't think before he types. You on the other hand just neg repped me because Kenan is crying to you so if anyone is abusing the system it is you. Stick to moderating your squad and not my forum activities.

[Guest Cali]

Can't we all just get along :cheer3nc:

[Crusty]

Can't we all just get along :cheer3nc:

 

Is that a question?...I think we need a poll:unsure: