The common misconception about stealth is that stealth makes you radar invisible; it doesn't. It significantly reduces your detection range versus radar, meaning that you will be able to see the other guy before he can see you. This means you can fire your missiles off, then flee before he can obtain a lock on you, effectively allowing you to out-range opponents without stealth capabilities. In an air-to-ground context this allows you to attack targets you would not otherwise be able to attack, and in an air-to-air context, this allows you to fire first and run away first. All of the anti-stealth radar systems are ultimately workarounds; there's a reason radars are X-band or Ku-band; higher frequency radars provide higher resolution and thus allow you to detect opponents at larger ranges. By going down to L-band, you can extend range versus an X-band or Ku-band radar, but you'll have reduced detection range in comparison to an X- or Ku-band system anyways.
Stealth Discussion
- Thread starter MiG-29
- Start date
IronsightSniper
Junior Member
Passive radar is not a new threat as the PAK-FA has been showcasing wingtip L-Band passive radars for a while now; like Inst said, they are superior to X-Band and Ku-Band radars at detecting low-RCS targets like a F-22, but they both lack range and 'assured' detection capability in comparison to other bandwidths such as the much coveted UHF band, which can essentially detect any stealth fighter as we know it (the problem is that you'd detect all the birds and other small things in the air, too).
Answering an earlier question, if a J-20 showed down with a F-22, it all depends on avionics at that point, to which information is sparse as the J-20's AESA is apparently still in development, so comparisons shouldn't be made yet. At that point, detection would depend on either EO sources (to which the J-20 has the advantage of having an EO sensor, and the F-22 doesn't), or off-board detection, which the U.S. has the advantage of most of the time (thanks to the overly large navy able to bring AWACs anywhere at anytime compared to the PLAAF only having a handful of AWACs even in service). The problem then would be missile ranges, and AFAIK, the AMRAAM's latest model outranges the PL-12 (I couldn't find info on the PL-21) by about 20 km. The final problem, then, is that as both missiles only have terminal-ARH, whoever shoots first will have to endur the possibility of being shot at simply because it's been guiding it's missile along. As both missiles have terrible terminal-phase performance, both planes could more than likely dodge the missile. The same scenario would occur against the PAK-FA, except it has the added advantage of L-band radars, which wouldn't be effective until, IIRC, about 60 km range.
Answering an earlier question, if a J-20 showed down with a F-22, it all depends on avionics at that point, to which information is sparse as the J-20's AESA is apparently still in development, so comparisons shouldn't be made yet. At that point, detection would depend on either EO sources (to which the J-20 has the advantage of having an EO sensor, and the F-22 doesn't), or off-board detection, which the U.S. has the advantage of most of the time (thanks to the overly large navy able to bring AWACs anywhere at anytime compared to the PLAAF only having a handful of AWACs even in service). The problem then would be missile ranges, and AFAIK, the AMRAAM's latest model outranges the PL-12 (I couldn't find info on the PL-21) by about 20 km. The final problem, then, is that as both missiles only have terminal-ARH, whoever shoots first will have to endur the possibility of being shot at simply because it's been guiding it's missile along. As both missiles have terrible terminal-phase performance, both planes could more than likely dodge the missile. The same scenario would occur against the PAK-FA, except it has the added advantage of L-band radars, which wouldn't be effective until, IIRC, about 60 km range.
Kurt
Junior Member
This is a short summary on developments of passive radar by Cassidian. The passive radar is not passive, but utilizes a cloud of signals from multiple, often unknown, sources of lower frequency than usual aircraft radars. Current structural and coating stealth is not suited to have much observeability negating effect on these. The system with its difficult algorithms requires lots of computing power and is part of the Eurofighter avionics. Now the company tries to increase the range of applications.
Naming it passive radar is rather misleading, just like stealth is low observeability. It uses active emissions not primarily intended as radar and computes from the radiation interference the location of objects to a degree sufficient to vector other detection devices.
In this combination passive radar and the PIRATE optic detection give the Eurofighter a good chance of situational awareness, including of aircrafts of currently high stealth technology standards.
The weakness of this approach is that you need radiation sources that do exist in Central Europe as long as the power grid supplies them, but do they exist in the middle of the Atlantic? You can eliminate much of a passive radar approach by shutting down the power grid - leaving fewer emitters that have a grid independent supply. The fewer emitters there are, the closer the problem is to previous select elimination of military emission sources. For detection applications it needs friendlies sending their radio signals, so it is of reduced use during invasions or in emission deserts with low population density - Canada?
Cassidian has made a name with that system, but they are not the only company active in this field and there's a claim that a Czech system was sold to the PRC (I doubt it).
One development that seems easy to predict is that old and still functional civilian radiation emission equipment in numbers together with suitable independent electricity supply will form a resilent wartime emission system. It can contain very mobile and small sources if they send an encoded constant position signal derived from the usual satellite positioning systems(GPS &Co.).
Because of available bandwidth someone will likely give them more information on conditions (the weather) to transmit for easier calculation by the "passive radar" system. Further information can be derived from observation, like electromagnetic spectrum and optic observation, thus having an area network that can rapidly vector optics on radar contacts and transmit local SIGINT under suspicious circumstances to strong computing centers.
A short note on German and English:
If a German says "something is overwhelming" he does a word for word translation of a typical German expression "etwas ist überwältigend". If he would have instead translated the meaning of this expression from German into English, he would say "something is astonishing/magnificient". The F-22 is truly astonishing.
Last edited:
Engineer
Major
Re: J-20 The New Generation Fighter Thread IV
As made clear in post #1904, the reason "you can absolutely predict how the other guy's technology will behave" is that "laws of physics is the same to everybody". As such, the knowledge and experience from the J-20 program can be applied in figuring out F-22's RCS.
I have not misrepresented anything so there is no need for me to retract something which is true
Having already built the J-20, Chinese engineers would have a lot of expertise in the effects of RAM. Yet, you constantly perpetuate the view that the experts would get over 90% of the RAM's effect incorrect. Such assumption defies common sense unless there is an intention to paint these experts as amatures.
Ironically, your use of "one has to" is placing a limitation, which goes completely opposite to the meaning you quoted from the dictionary. With "no qualification, restriction, or limitation", one would not be restricted to using "the exact same pieces of technology".
As made clear in post #1904, the reason "you can absolutely predict how the other guy's technology will behave" is that "laws of physics is the same to everybody". As such, the knowledge and experience from the J-20 program can be applied in figuring out F-22's RCS.
Last edited:
Skywatcher
Captain
Re: J-20 The New Generation Fighter Thread IV
You're moving the goal posts again. The "no qualification, restriction, or limitation" definition of absolute applies to your "predictions" about the other guy's technology, unless you're precognitive
And given that the J-20 is still well in the R&D phase, how do they already have the spare expertise to go and calculate the F-22's RCS, even if the two fighters use the same stealth technology (the F-22 and F-35 use completely different RAM approaches for starters)?
Doubling the RCS of a 5th generation fighter does matter.
Rebecca Grant states in The Radar Game, published by the Mitchell Institute, that a 40% reduction in RCS leads to a 10% decrease in detection range. Let's take a thought exercise here.
Now let us assume that there are two fifth generation fighters, A and B, going head to head in combat, both supercruising at Mach 1.5. (about 1830km per hour).
Fighter A's radar can detect a 0.025m2 sized target at 60km. But contrary to what the lead contractors of Fighter A thought, Fighter B's RCS is not 0.025m2 but 0.015m2 and thus Fighter A only detect. Fighter B can detect Fighter A at 60km, since Fighter A's RCS is actually 0.025m2.
In those six seconds* where Fighter B can detect Fighter A (but not vice versa), Fighter B can shoot a BVRAAM at Fighter A. An AMRAAM has a speed of Mach 4 (4900kmh), so Fighter B's BVRAAM will have traveled 8km before Fighter A can even shoot back. This leaves Fighter A at a great disadvantage, to put things mildly.
*Both fighters are going at a speed of about 0.5km a second heading towards each other, so covering a 6km gap will take 6 seconds. It could be possible for Fighter B to try to maneuver to stay at least 54km away from Fighter A while maintaining a radar lock to lengthen that window.
And where have I asked for a perfect model, pray tell? In your imagination?
And where did you pull this 90% figure out of? Your nether regions?
You're moving the goal posts again. The "no qualification, restriction, or limitation" definition of absolute applies to your "predictions" about the other guy's technology, unless you're precognitive
And given that the J-20 is still well in the R&D phase, how do they already have the spare expertise to go and calculate the F-22's RCS, even if the two fighters use the same stealth technology (the F-22 and F-35 use completely different RAM approaches for starters)?
Doubling the RCS of a 5th generation fighter does matter.
Rebecca Grant states in The Radar Game, published by the Mitchell Institute, that a 40% reduction in RCS leads to a 10% decrease in detection range. Let's take a thought exercise here.
Now let us assume that there are two fifth generation fighters, A and B, going head to head in combat, both supercruising at Mach 1.5. (about 1830km per hour).
Fighter A's radar can detect a 0.025m2 sized target at 60km. But contrary to what the lead contractors of Fighter A thought, Fighter B's RCS is not 0.025m2 but 0.015m2 and thus Fighter A only detect. Fighter B can detect Fighter A at 60km, since Fighter A's RCS is actually 0.025m2.
In those six seconds* where Fighter B can detect Fighter A (but not vice versa), Fighter B can shoot a BVRAAM at Fighter A. An AMRAAM has a speed of Mach 4 (4900kmh), so Fighter B's BVRAAM will have traveled 8km before Fighter A can even shoot back. This leaves Fighter A at a great disadvantage, to put things mildly.
*Both fighters are going at a speed of about 0.5km a second heading towards each other, so covering a 6km gap will take 6 seconds. It could be possible for Fighter B to try to maneuver to stay at least 54km away from Fighter A while maintaining a radar lock to lengthen that window.
Skywatcher
Captain
Re: J-20 The New Generation Fighter Thread IV
Addendum:
There are multiple types of RAM out there.
You have myriad types of iron ball paint absorbers, and carbon black particles, and then there are new exotic materials derived from nanotechnology (there are claims to use active RAM, but I don't think that's actually practical for the near future).
And then you can utilize the RAM either as a coating (see F-117, B-2, F-22) or "bake" it into the skin (F-35).
This is complex, multiple input technology with constant changes in state of the art (hence, why material science graduates are paid big bucks by the likes of LM, Boeing, CAC and Sukhoi).
As Chinese engineers build the J-20 and other projects, they have definitely conducted research into RAM (several types, probably). But as we have seen, there are multiple ways to skin the RAM cat (apologies to all cat lovers out there). Do you really think that there are enough Chinese scientists and resources out there to conduct exhaustive research on RAM types not of manufacturing interest to AVIC, and then report with 90%+ confidence on the F-22's RAM (which mind you, undergoes planned upgrades)?
Addendum:
There are multiple types of RAM out there.
You have myriad types of iron ball paint absorbers, and carbon black particles, and then there are new exotic materials derived from nanotechnology (there are claims to use active RAM, but I don't think that's actually practical for the near future).
And then you can utilize the RAM either as a coating (see F-117, B-2, F-22) or "bake" it into the skin (F-35).
This is complex, multiple input technology with constant changes in state of the art (hence, why material science graduates are paid big bucks by the likes of LM, Boeing, CAC and Sukhoi).
As Chinese engineers build the J-20 and other projects, they have definitely conducted research into RAM (several types, probably). But as we have seen, there are multiple ways to skin the RAM cat (apologies to all cat lovers out there). Do you really think that there are enough Chinese scientists and resources out there to conduct exhaustive research on RAM types not of manufacturing interest to AVIC, and then report with 90%+ confidence on the F-22's RAM (which mind you, undergoes planned upgrades)?
Engineer
Major
Re: J-20 The New Generation Fighter Thread IV
If you are wondering where I get the 90% figure from when I said you are portraying Chinese experts as a bunch of amatures, your above post would be it.
Previously, we have learned that 90~95% of the stealth comes from shaping. This puts the remaining 5~10% as effects from RAM. In other words, by assuming there to be a 10% miscalculation in RCS estimation, your thought experiment assumed the Chinese engineers to be so incompetent that their estimations would miss the effects from RAM entirely. Your experiment isn't realistic to begin with. Additionally, there are three other problems.
First, there is a difference between detection and lock. This was brought up very early on when the scans from a Chinese paper was posted. As opposed to your imagination, your fighter B will not enjoy the advantage of launching any missile right after detection.
Second, BVRAAM does not have an initial speed of 4900 km/h. The missile has to accelerate, so the actual range traveled by the missile would actually be less than 8 km.
Thirdly, a fighter cannot maintain 54km away while presenting the least RCS simultaneously. If Fighter B turns, RCS would not be minimal. If Fighter B maintains its heading, the distance will close rapidly and the engagement will become WVR.
Firstly, I have explained in one of my previous posts that in post #1869, your ally expected every single details to be replicated, which would result in a perfect model. Secondly, you are making a big deal out of any deviation in the last few percents of RCS estimation. Anyone who is not expecting perfection will find that small of a deviation as being acceptable.
Nope. First of all, your definition has nothing to do with the statement "you can absolutely predict how the other guy's technology will behave". Secondly, your interpretation of the dictionary was entirely opposite to what the dictionary is saying. There is no such requirement of "using the exact same pieces of technology", not even according to the dictionary, as the meaning is entirely your invention.
Firstly, estimating RCS does not require all the fighters to use the same pieces of technologies. We are talking about estimates, not exact values. Second, there exist expertise for China to drawn upon, irrespectively of whether they are spare. What you have brought up here is non-issue.
If you are wondering where I get the 90% figure from when I said you are portraying Chinese experts as a bunch of amatures, your above post would be it.
Previously, we have learned that 90~95% of the stealth comes from shaping. This puts the remaining 5~10% as effects from RAM. In other words, by assuming there to be a 10% miscalculation in RCS estimation, your thought experiment assumed the Chinese engineers to be so incompetent that their estimations would miss the effects from RAM entirely. Your experiment isn't realistic to begin with. Additionally, there are three other problems.
First, there is a difference between detection and lock. This was brought up very early on when the scans from a Chinese paper was posted. As opposed to your imagination, your fighter B will not enjoy the advantage of launching any missile right after detection.
Second, BVRAAM does not have an initial speed of 4900 km/h. The missile has to accelerate, so the actual range traveled by the missile would actually be less than 8 km.
Thirdly, a fighter cannot maintain 54km away while presenting the least RCS simultaneously. If Fighter B turns, RCS would not be minimal. If Fighter B maintains its heading, the distance will close rapidly and the engagement will become WVR.
Re: J-20 The New Generation Fighter Thread IV
Not speaking for Engineer, but yes. In fact I do. Not only has the pace of research quickened due to advances in computing, but RAM isn't even really at the fringe of the most difficult material science research. There's a case to be made that it's very difficult to design a RAM that has the best absorption properties and can still fulfill all the necessary requirements for application onto a fighter, but thankfully, with simulations you only need to worry about the absorption properties and not everything else.
Engineer
Major
Re: J-20 The New Generation Fighter Thread IV
There is nothing to prevent Chinese engineers from revising their estimates every so often, using the latest information that are available. F-22 and F-35 will have to go through physical implementations, where methods are engineered to manufacture the coating then having the coating applied onto actual aircraft. Estimation can be done without such physical implementation, so will actually be closer to the state-of-the-art.
There is nothing to prevent Chinese engineers from revising their estimates every so often, using the latest information that are available. F-22 and F-35 will have to go through physical implementations, where methods are engineered to manufacture the coating then having the coating applied onto actual aircraft. Estimation can be done without such physical implementation, so will actually be closer to the state-of-the-art.
Skywatcher
Captain
Re: J-20 The New Generation Fighter Thread IV
Not only do you have to look at the various types of RAM, you have to examine how it interacts with the materials used on the aircraft skin.
Not only do you have to look at the various types of RAM, you have to examine how it interacts with the materials used on the aircraft skin.