Raptor / Stealth question

I have just been reading an AFM report on the Typhoon and it has raised some questions in my mind about the Raptor that someone here may be able to answer for me.

It states that the Typhoons CAPTOR radar is virtually its secondary detection system as the PIRATE IRST is so sophisticated it can detect not only the targets engine exhaust heat but also the heat from the target aircrafts skin which is generated by the friction caused by simply moving through the air. Whats more, PIRATE can track up to 200 targets up to 145Km away without giving away the presence of the Typhoon by this completely passive method.

Now this would seem to suggest that Typhoon can passively detect anything, even a Raptor, Maybe, maybe not but the question I have relates to the much acclaimed 'first look, first shot, first kill' attribute of the Raptor and its radar which we are told will allow the F/A-22 to get off a shot before the enemy knows it is there.

Wouldn't the Raptor simply give itself away by using radar in the first place? Aren't the emissions from the nose a dead giveaway, totally negating all stealth attributes of the aircraft?

I'm sure this has been thought of, I'm not here to knock the Raptor, but how does it get round this? Does it have something akin to the PIRATE itself? I have read that some technology on the Typhoon (though nothing specific) is so advanced that it has been incorporated into the F/A-22 in order to enhance its capabilities still futher so maybe this could be the case?

Also, somewhat mysteriously given the 'no gun' thread about the Typhoon this report spells out why the RAF version of the Typhoon is the most sophisticated and capable version of the type to be built with some truly awesome tech which the other partners have simply left out, makes you wonder why, or even if, they have left the gun as useless, as has been reported.

Originally posted by waynos
Wouldn't the Raptor simply give itself away by using radar in the first place? Aren't the emissions from the nose a dead giveaway, totally negating all stealth attributes of the aircraft?

I don't know enuf about either systems to comment on the IR aspect, but the radar I will comment on. The Raptor will have a LPI or low probability of Intercept radar system. Also, if there is Awacs coverage, the Raptors can crossdeck the feed from them and passivly sneak up on targets without using its radar.

Stealth doens't mean only radar stealth, it's also IR reduction. The main reason why the Raptor is not flying above than Mach 2 is the IR reduction. Also F-22 flies at 16km alt., where is much thinner air.

P.S. F-22 and also SuperHornet have both very advanced IR sensors, and other modern planes too. The main reason why there is so much talk about it in Eurofighter's case is that EF other features are not interesting enough (no offense, I meant it's pretty conservative aircraft - no stealth, no thrust vectoring etc.) so EF engeneers are talking about such "inovations" like fly-by-wire, unstable aerodynamics, advanced computers ). I don't say that the EF has bad avionics, it's just booring when it's referred as something revolutionary.

The F-22 radar is hard to detect, because it always changes it's frequencies (computer generated random pattern) and has low EM signature.

Originally posted by longbow
Stealth doens't mean only radar stealth, it's also IR reduction. The main reason why the Raptor is not flying above than Mach 2 is the IR reduction. Also F-22 flies at 16km alt., where is much thinner air.

It doesn't matter how many aspects there are to the stealthiness of the emitting aircraft, its radar acts like a lighthouse, that was what I was asking about.

P.S. F-22 and also SuperHornet have both very advanced IR sensors, and other modern planes too.

The point about PIRATE is that it is the most advanced and capable on the planet, until the next one is invented, as always

The main reason why there is so much talk about it in Eurofighter's case is that EF other features are not interesting enough

(no offense, I meant it's pretty conservative aircraft - no stealth, this is just plain wrong

no thrust vectoring etc.) this is coming with tranche 3 and as a retrofit on previous aircraft
so EF engeneers are talking about such "inovations" like fly-by-wire, unstable aerodynamics, advanced computers

). I don't say that the EF has bad avionics, it's just booring when it's referred as something revolutionary.

I am led to believe that you get your knowledge of the Typhoon from the Daily Express or some such publication. No offence is intended but your assertions are too far wide of the mark to be taken as a serious answer on thuis subject

The F-22 radar is hard to detect, because it always changes it's frequencies (computer generated random pattern) and has low EM signature.

Now that smore like what I was after, actual F/A-22 information, if slightly vague.

Fred T, yes that is one solution, it is also available to Typhoon too, but is there a way for the Raptor to use its own radar and still maintain a stealthy profile is the real question, I suppose.

[edit on 21-8-2004 by waynos]

Lets bear in mind that 'stealth' does not equate to 'invisibility' but more to 'reduced visibility'. There are many ways in which a stealth plane could be detected, ambient heat generated from the airframe is one of them.

Stealth planes cannot 'roam' over enemy territory without a huge amount of planning, and they have to stick to their planned routes like glue. This is because their stealth characterisitics do not make enemy radar useless, but rather reduces their effective range, thus by flying outside this effective range you can fly between the 'danger areas'. The FA-22 is designed with air to air combat in mind, so it only has the enemy aircraft to worry about, but if its ever deployed in ground attack configurations, then it will be subject to the same rules as the B-2 and F-117 - that all missions are essentially point to point flying with very little leeway in what the pilot can do.

The Raptor could be effectively engaged by using a distributed targetting system. 3 or 4 high powered radar systems onboard seperate aircraft could produce enough of a return off a Raptor for intercepting aircraft can gain missile lock. There are several nations in the world which is persuing such an integrated system (which goes far beyond AWACs type solutions).

Another solution ive heard of is a radar based scatter system which measures air pressure. Due to the nature of how an aircraft flies, it would be very hard to hide the disturbance that your aircraft creates when flying, thus giving you away. Natural disturbances could be ruled out because the pressure signature generated by aircraft are unique to each type.

The thing that stealth designers bank on when designing a stealth aircraft is not that the plane is invisible, but that known means of detecting such aircraft would also produce radar returns off of other objects, for example birds. Its well known that you can get a usable radar return off of a F-117 just by increasing the radars power, but doing so means you need to pick out the F-117 from the clutter, like birds or cars on highways etc. With increasing computer power and new algorithms, this is quickly becoming a non problem for radar designers.

Its probable that the PIRATE system was never realised as a threat when the FA-22 was designed, and that in future models you may see a helium skin cooling system being implemented.

So what your saying is that "stealth" is ectually useless because they cant fly through the so called "danger areas", so basicly i can send anything as long as it flies without the effective range of the radar?!

the way AA stuff is set up, radar usually overlaps slightly to make sure that nothing can get through. What stealth does is basically to make the radius much smaller for that particular aircraft then what it would be for a normal one. So say there are 2 radar stations 100 miles apart. they each have a radius of 60 miles so there is a 20 mile overlap. What the stealth would do is make each radars radius only be able to pick up the raptor if it was say 30 miles away or closer. Thus, there is a 40 mile gap between the 2 radar stations that allow a raptor, jsf, F-117 or b-2 to get through undetected.

Note that the JSF and F-17 stealth is inferior to that of the Raptor and B-2.

From what I have read, the Raptor is so stealthy, that F-15's were in VR and the raptor was not detected

Wouldn't the Raptor simply give itself away by using radar in the first place? Aren't the emissions from the nose a dead giveaway, totally negating all stealth attributes of the aircraft?

In a word no. The Radar uses such wide frequencies that it is very difficult to detect.

I'm sure this has been thought of, I'm not here to knock the Raptor, but how does it get round this? Does it have something akin to the PIRATE itself? I have read that some technology on the Typhoon (though nothing specific) is so advanced that it has been incorporated into the F/A-22 in order to enhance its capabilities still futher so maybe this could be the case?

Yes, the Raptor obviously will have something akin (if not more advanced) to this. There is no reason, or way for that matter, that the US would not incorporate such technology. Furthermore, one main doctrine of the US millitary is redudancy of systems, which further indicates it would have more or less the same tpe of system.

If you are really interested in the F/A-22 Radar read this:

AN/APG-77 Radar

The AN/APG-77 radar is the F-22�s primary sensor and is a long-range, rapid-scan, and multi-functional system. A Northrop Grumman-led joint venture with Raytheon is developing the active-element electronically scanned array radar. Northrop Grumman is also responsible for the radar sensor design, software, and systems integration.

The AN/APG-77 radar is an active-element, electronically scanned (that is, it does not move) array that features a separate transmitter and receiver for each of the antenna's several thousand, finger-sized radiating elements. Most of the mechanical parts common to other radars have been eliminated, thus making the radar more reliable. This type of antenna, which is integrated both physically and electromagnetically with the airframe, provides the frequency agility, low radar cross-section, and wide bandwidth necessary to support the F-22's air dominance mission. The radar is key to the F-22's integrated avionics and sensor capabilities. It will provide pilots with detailed information about multiple threats before the adversary's radar ever detects the F-22.

The AN/APG-77 radar a novel type of electronically scanned phased array. In what is likely to be the most advanced airborne radar in the world, individual transmit and receive modules are located behind each element of the radar array. The transmit function of the solid-state microwave modules supplants the traveling wave tubes used in prior radars like the APQ-164. The active, electronically scanned array (ESA) configuration has a wider transmit bandwidth while requiring significantly less volume and prime power. The system represents about half the weight of an equivalent passive ESA design. Each of the hundreds of individual solid-state devices generates only small amounts of power, but the aggregate for the entire array is substantial.

The F-22 s APG-77 electronically scanned array antenna is composed of several thousand transmit/receive modules, circulators, radiators and manifolds assembled into subarrays and then integrated into a complete array. The baseline design used thousands of hand-soldered flex circuit interconnects to make the numerous radio frequency, digital, and direct current connections between the components and manifolds that make up the subarray. Northrop Grumman Corporation, of Baltimore, MD, has developed an improved manufacturing process for F-22 aircraft radar components. The new process could result in a cost avoidance of nearly $87 million on the planned production run for the aircraft. By replacing the hand-soldered flex circuit interconnects with automated ribbon bond interconnects, the first pass yield of the subarray assembly has been vastly improved.

The AN/APG-77 radar antenna is a elliptical, active electronically scanned antenna array of 2000 transmitter/receive modules which provides agility, low radar cross section and wide bandwidth. The radar is able to sweep 120 degrees of airspace instantaneously. In comparison to the F-15 Strike Eagle's APG-70 radar takes 14 seconds to scan that amount of airspace. The APG-77 is capable of performing this feat by electronically forming multiple radar beams to rapidly search the airspace.

The system exhibits a very low radar cross section, supporting the F-22's stealthy design. Reliability of the all-solid-state system is expected to be substantially better than the already highly reliable F-16 radar, with MTBF predicted at more than 450 hours.

The APG-77 radar offers significant advantages over previous combat radars. Among its most attractive benefits is the integration of agile beam steering. This feature allows a single APG-77 radar to carry out multiple functions, such as searching, tracking, and engaging targets simultaneously. Agile beam steering also enables the radar to concurrently search multiple portions of airspace, while allowing continued tracking of priority targets.

The Low Probability of Intercept (LPI) capability of the radar defeats conventional RWR/ESM systems. The AN/APG-77 radar is capable of performing an active radar search on RWR/ESM equipped fighter aircraft without the target knowing he is being illuminated. Unlike conventional radars which emit high energy pulses in a narrow frequency band, the AN/APG-77 emits low energy pulses over a wide frequency band using a technique called spread spectrum transmission. When multiple echoes are returned, the radar's signal processor combines the signals. The amount of energy reflected back to the target is about the same as a conventional radar, but because each LPI pulse has considerably less amount of energy and may not fit normal modulation patterns, the target will have a difficult time detecting the F-22.

The F-22 and its APG-77 radar will also be able to employ better Non-Cooperative Target Recognition (NCTR). This is accomplished by forming fine beams and by generating a high resolution image of the target by using Inverse Synthetic Aperture radar (ISAR) processing. ISAR uses Doppler shifts caused by rotational changes in the targets position to create a 3D map of the target. The target provides the Doppler shift and not the aircraft illuminating the target. SAR is when the aircraft provides the Doppler shift. The pilot can compare the target with an actual picture radar image stored in the F-22's data base.

There is plenty more where that came from...

Originally posted by RichardPrice


Another solution ive heard of is a radar based scatter system which measures air pressure. Due to the nature of how an aircraft flies, it would be very hard to hide the disturbance that your aircraft creates when flying, thus giving you away. Natural disturbances could be ruled out because the pressure signature generated by aircraft are unique to each type.

The airframe F-22 was designed to create minimal turbulences. I don't know how good it works.

Its probable that the PIRATE system was never realised as a threat when the FA-22 was designed, and that in future models you may see a helium skin cooling system being implemented.

Wrong, the IR detectors have been realised as a potencional threat. The F-22 HAS reduced IR signature because of :
1. engines placed deep into the fuselage.
2. leading edges are fuel cooled
3. supercruise (less need for afterburner with high IR)
4. less visible engine exhaust
5. special coatings - this coatings are changing the frequencies of IR emisions so that the IR emisions with new frequencies tends to be faster absorbed by the atmosphere.


This means the F-22 is very hard to detect by IR sensors especially in "head-to-head" view.

so mad man your saying that if i had like a radar that has a radios of lets say a 100miles and i let a stealth plane fly over or something it will detect it?? thats quite unbelieveble.

Originally posted by longbow

The airframe F-22 was designed to create minimal turbulences. I don't know how good it works.

I wasnt talking about turbulences, I was talking about the pressure differences that occur between the upper and lower surfaces of the wing. You cant eliminate these types of disturbances due to the very physics of flight

Wrong, the IR detectors have been realised as a potencional threat. The F-22 HAS reduced IR signature because of :
1. engines placed deep into the fuselage.
2. leading edges are fuel cooled
3. supercruise (less need for afterburner with high IR)
4. less visible engine exhaust
5. special coatings - this coatings are changing the frequencies of IR emisions so that the IR emisions with new frequencies tends to be faster absorbed by the atmosphere.


This means the F-22 is very hard to detect by IR sensors especially in "head-to-head" view.

From what I understand, PIRATE is no ordinary IR detection system. Its an advanced system that goes far beyond normal IR detection systems, and this may be where the F-22 falls down. The F-22 design is pretty much nearing 10 years old at the moment, whereas PIRATE is pretty damn new, so its conceivable that the F-22 design doesnt incorporate anti PIRATE features simply because its not that easy to follow cutting edge technology that quickly.

Again, Im only guessing, but it seems logical. At some point in the Raptors design, it needs to be finalised as a block number, so it can go into production. At this point there will always be new technology that has the potential to defeat what has gone before. It will catch up with developments in later block numbers and upgrades.

[edit on 26-8-2004 by RichardPrice]

Originally posted by 187onu
so mad man your saying that if i had like a radar that has a radios of lets say a 100miles and i let a stealth plane fly over or something it will detect it?? thats quite unbelieveble.

OK, let me see if I can explain this better....

Lets say a radar has a range of say 100 miles. What stealth tech does is cut the range that a radar can pick up the return signal.

So in this case, a radar with a range of 100 miles on regular planes would only be able to pick up the Raptor (or any other stealth plane) if it was 50 miles or closer. It does not mean that a plane can just fly over any radar and not be detected, it means that a stealth plane can get much closer to a radar before it is detected.

let me draw something for ya.

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
| |
| P |
| |
| S |
| T |
| |
| |
| |
| |
|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ |




scale 2/1000
P=plane
S=sam or any surface-2-air missile
T=target

so mad man ur telling me that if a stealth plane comes into the range (50miles) it will be detected and probably shot down, in other words there is no way u can shoot the target (unless u fire it from like really far which is impossible)


[edit on 26-8-2004 by 187onu]

[edit on 26-8-2004 by 187onu]

[edit on 26-8-2004 by 187onu]

[edit on 26-8-2004 by 187onu]

[edit on 26-8-2004 by 187onu]

[edit on 26-8-2004 by 187onu]

[edit on 26-8-2004 by 187onu]

[edit on 26-8-2004 by 187onu]

[edit on 26-8-2004 by 187onu]

OK, I will do my own little diagram

picture this line as the range of a radar. The "R" is the radar site, the "N" is a normal aircraft, which is predictably picked up at the max range of the radar. The "S" is a stealth plane, which as you can see is picked up on the radar at a much shorter distance. Basically, when a plane is stealthy, it reduces the effective range of a radar, and thus allows the plane to get much closer to the target without being detected.

Also, stealth involves the heat signature of an aircraft, because there are heat seeking missles, so this is involved as well.




N___________________________S___________R

[edit on 26-8-2004 by American Mad Man]

[edit on 26-8-2004 by American Mad Man]

how da # do u know this?

i liked me diagram better

[edit on 26-8-2004 by 187onu]

Well, the basics of it are not classified, but the numbers are

BTW, I liked yur diagram better too

I was too inept to do a 2D one, so I had to just use a line

Stealth does not mean invisible, it mean harder to detect. The fourth root law of RCS means you have to reduce the radar cross section by a factor of 1000 to get a 90% reduction in detection and/or tracking ranges. It is possible to detect a stealth aircraft from time to time at a useful range, but chances are you'll simply ignore it as hash. It is when you can track an aircraft that you've got a real ithreat issue.




The diagram reads as follows:

A hypothetical radar can detect or track 10m sq RCS aircraft at 180 km, reducing the RCS in half (which is quite difficult) only reduces the detection range by 30 km. It is possible to reengineer an airframe so it has some low observable characteristics, like what happened between B-1A and B-1B and the F-18C and F-18E. They are not stealth aircraft, they only have been tweaked to the limit of conventional design to reduce their detectability. Of course once you hang stores off your Super Hornet it won't be stealth at all, the RCS of pylons and missiles would be more than the whole of the rest of the carrier aircraft put together, all those nasty right angles.

To get meaningful reductions in detection and tracking you need to go for full stealth design, reduce RCS by a factor of 1000 or what's called in the LO offices as a 30dB reduction. That way you can get through definsive SAM sites, or get MUCH closer to a defended position and take it out. That's why the F/A-22 is earmarked to be the next Wild Weasel type aircraft. When its not shooting fighters or dropping JDAM's it has everything needed to be a SAM buster. Integrated avionics, sensor fusion, it has a God's Eye View of the radar installations, automatically putting each into a shoot list just like it does in the air dominance role. The F-4's needed to be crammed with all kinds of gear with a GIB to operate the stuff. It's all automated now in the Raptor. Just a software upgrade, a version of HARM with smaller fins for internal carriage or some newer antiradiation missile and it can kill just about any air defence system around.

Very low frequency radars are a different matter, because of how the low frequencies react to radar absorment materials is far less attenuated than higher frequency tactical defence systems they'll need to use a different tactic, probably cruise missiles which home in on those types hugging the ground.

Originally posted by 187onu

so mad man ur telling me that if a stealth plane comes into the range (50miles) it will be detected and probably shot down, in other words there is no way u can shoot the target (unless u fire it from like really far which is impossible)

Bear in mind that with almost all SAM systems there is a cone above the site within which the system cannot detect anything. The idea of stealth is that the effective range is reduced enough that the aircraft can get into this zone, hit the target and escape, or go round the SAM site and hit the target.

Here's very nice page about RCS:
www.aerospaceweb.org...

Stealth aircrafts have RCS in class of birds which makes it hard to get enough return for detecting it, and with big enough transmitting powers radar also sees birds and that kind of things which cause need for for some heavy processing to discriminate plane from all that background.

Waynos,

First off, never give full credit to something AFM states until you check it with at least two other sources. ;-) In particular, they vastly overrate both the Typhoon and the Su-30 as 'point comparison' justifiers for the threat which the F/A-22 is needed to counter.

Second IR radition is funny for it's responses to varying atmospheric conditions with an inordinantly large part of the spectrum absorbed by air (much like UV) My recollection is of two wave bands between 3-5u and 9-14u by which you can normally detect hot vs. cool objects with varying filter settings to screen out background (blackbody 'spot glare') of clouds etc..

Longwavelength systems don't have the best range but do better with moisture/obscurrant defeat. Short/Mid wavelength systems do very well for range and scattering (Mie not Raleigh IIRR) but tend to be quickly absorbed by heavy particulate or water vapour fractions and can even bend a bit through normal thermal layering.

It's the 'hand behind the thumb' theory of putting an IR point source at sufficient distance from the detector that even a few stray molecules can 'block' (refractively scatter or absorb) the energy of the signature and these are such unmappable, effectable elements of the environmental background that you can do very little to improve the sensor itself to compensate. Either the energy is there. Or it ain't.

Hence, unless you are at VERY great height (cold and dry), looking at equivalent altitude targets, your detection range is 'going to vary verily'. I would put numbers in the mid to low 30nm category when compared to say the F-14 TCS with IR-CCD upgrade which should be about 50nm, for larger targets.

I would also definitely question the notion of shifting IR radiant heat into another frequency as most IR theory (Kirchoff's Law etc.) centers on the notion that you can't be an Absorber and an Emitter in anything but balanced quantities without increasing local surface temperature and hence altering the bandwidth properties of the object as a whole.

I know that's the excuse they use for the Raptor's 'Top Coat' but I don't really give it much credit.

While you can do a lot of things to amplify a baseline signature (a decent pair of Gen-III goggles will pick up an airliner nav beacon at 80nm and flash it like a visual strobe from a lighthouse at 10), you usually cannot alter the direct emissivity of something without changing the chemical consistency of it.

That said, the ATF spec originally called for an EOSS or Electro Optical Sensor System imbed (for which power and processing still exist on the SEM-E cards) but this was cancelled early in the program due to problems with getting the system to provide decent detection distances (Over Cloudy, Wet, Europe) overlapping the ranges for which the ATF was originally expected to be able to fire at.

(I have also heard RFLO edge control 'seam' excuses and of course 'too expensive' alternatives).

The two wingroot fairings which were originally intended for this system now appear to be dielectric radomes for either some kind of 2D ISAR identification system. Or perhaps some kind of active/passive adjunct to the ALR-94. In the F-15E and Rafale, similar locations are used for so called 'active cancellation' jammer installations. But my bet is on something equivalent to the ALQ-128 doppler ID system on the F-15.

What is clear is that, from Mach 1.5 preenergization, even with a conventional AIM-120C5, you are looking at a 40nm FQ outerenvelope and probably at least 25 NEZ. With the later AIM-120C7 (better kinematic controls in the autopilot and 'I am here, which volume point do I steer to?' 2-way datalink) and the AIM-120C8 (now D, with a new motor, possibly gel-based). This figure should go up to well over 80. I know it's supposedly close to 50, even on the F/A-18E/F for which it was developed.

The Eurofighter cannot compete with this without itself going supersonic and it will forever be at a disadvantage in both decreasing sensor efficiency as the PIRATE ball heats. And in 'boar spear' impaling itself on it's own velocity vector. The Meteor/BVRAAM (with it's own passive range-known steering datalink option and ramjet propulsion) may make up for a part of this but the F/A-22's will always be able to defeat a basic 'search to acquire' seeker lightoff by volume index changes and crank slowdowns while, if you split the engagement out to perhaps 20-40nm, and 5-15K altitude there is equally a good chance that the IRST field of view will be 'pulled', along with the Typhoon's nose, into tracking Raptor A, only to allow Raptor B to move in from a different altitude/range/azimuth offset (all coordinated by AWACS).

Indeed, the digital datalink theoretically allows the F/A-22 to play 'shooter' fire and then immediately extend laterally away at full speed while another 'eyeball' (in-trail) provides the midcourse. Taking engagement distances up to 120-160nm, depending on how much credit you give the '270km effective' detection range listed for the APG-77.

In any case, provided the base signatures remain above 1m2, radar will always be the more useful targeting tool because it responds less to clutter in the lookdown mode and to weather. While sometimes the very intent to come through 'regardless' is best sent as a ' warning of deliberate move-or-be-mowed-down alternatives.

Tomcats approaching H3/H4 in 1991 did this very thing with their AWG's as part of 'brooming' the Iraqi fighters away from their home fields. Which were subsequently leveled.


KP