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Subject: When the Russians claim the S-400 can...
DarthAmerica    8/8/2007 7:05:39 PM
...defeat stealth aircraft, what are they basing that on? I understand that stealth aircraft arent really "invisible". Just return really low signals. So does the S-400 simply just use brute force or some some other method? Or is this simply marketing hype? -DA
 
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5thGuards       8/8/2007 9:09:40 PM
Using metric-wave anti-stealth radar and using special scanning intensities and ranges .. Little is known about these things..
 
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DarthAmerica       8/8/2007 9:45:38 PM

Using metric-wave anti-stealth radar and using special scanning intensities and ranges .. Little is known about these things..

Well actually a lot is know about these things. I'm not trying to be confrontational please understand. However I do know that stealth aircraft are designed with specific RF band in mind in order to detect aircraft. frequency band is selected based on certain criteria. So we aircraft designers make most stealth aircraft they "optimize" the design to counter those bands with various methods. So in theory, an aircraft that is "stealthy" in band A may be perfectly visible in band B. Due to physical limitations it is impossible to be stealthy to the entire spectrum through shaping(F-117). However my understanding is that later generation stealth aircraft which obviously do not rely totally on shaping are stealthy across a very wide range of frequencies. Also, intelligence gathering is very likely to have known about the s-400 during the design phase of that weapon. So some characteristics would be taken into account during the design of later generation stealth aircraft that fly now. Another thing is there is more to stealth than shaping and RAM. Things that are highly classified most likely.
So I wonder exactly what the Russians mean when they say the S-400 detects stealth aircraft. Also, do they mean detects stealth aircraft at operationally useful ranges. I could understand how an aircraft relying solely on shape and RAM could be more detectable. Even if so, physics would suggest that while certain stealth aircraft could be detected this way. The use of a different "type" of radar may mean very different performance chracteristics compared to traditional radar.
 
BUT because I only study radars as a hobby and very casually, I'm limited in my analysis.
 
-DA   
 
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displacedjim       8/8/2007 10:13:30 PM

...defeat stealth aircraft, what are they basing that on? I understand that stealth aircraft arent really "invisible". Just return really low signals. So does the S-400 simply just use brute force or some some other method? Or is this simply marketing hype?


-DA
 
GRAVE STONE, 96L6, and BIG BIRD are not LVHF radars, so they aren't gaining anything merely by going to very long wavelengths.  This isn't really my area but I'll start off the discussion by simplistically just suggesting what they have is better hardware and better processing techniques (less system noise generated within the radar, better filtering of the noise, better recognition of a target return signal amongst the noise, greater sensitivity within the radar to smaller signals) that decreases Smin (the minimum returned signal strength that can be processed by the radar), as well as better radiated signal waveforms and their attendant processing techniques that provide greater effective power (stuff that I can't properly explain like pulse packets, pulse coding, multiple frequencies, I don't know what else offhand because I'm not a radar engineer).  If you look at the radar range equation this will increase the maximum detection range for a given RCS.

 
 
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displacedjim       8/8/2007 10:26:35 PM

So I wonder exactly what the Russians mean when they say the S-400 detects stealth aircraft. Also, do they mean detects stealth aircraft at operationally useful ranges.

Eactly.  As you well know, it's not a matter of somehow the S-400 can see all stealth aircraft at all ranges.  Some threat radars (that means I'm not talking about nearly unique cases like an OTHB radar, but the radars associated with a SAM system for example) will never detect an LO aircraft in flight.  Some other threat radars will, but at best only within a dozen or a few dozen miles.  A few threat radars might be able to track some LO aircraft within several dozen miles.  The S-400 represents an improvement over older SAM systems for sure.  However, as a generalization I think it's reasonable to say the difference from older SAMs vs. an LO target to the S-400 vs. an LO target is still smaller than the difference from older SAMs vs. an LO target to those same older SAMs vs. a non-LO target.


 
 
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