A simple method to engage stealthy target

[Todjaeger]

There's rumors and claims of it but I don't have anything concrete. It's very likely, however, that PMU2 and above (S-400) do have the capability. How effectively they can employ it is another question.

I would honestly not be so certain that is does have an LPI capability. My doubt stems more from the potential 'value' of LPI radar for GBAD relative to developmental and operational costs than any capability or lack thereof to develop it.

A LPI radar in a LO/VLO aircraft is valuable, because it allows the aircraft to have some measure of sensing/SA via radar, without automatically revealing its presence because it is a radar emitter. The aircraft's radar itself can be LPI through a combination of aircraft speed and frequency-hopping steerable beams. In order for this to be done and also provide/return useful information, a series of potentially complicated algorithms need to be followed, to allow the T/R modules of the AESA to a given vector/volume of airspace while alternating the beams and frequencies used. Part of what can make this so complicated is that as differing frequencies are used, the avionics need to be able to correlate the transmitted signal with the received signal, across the range of frequencies used and their relevant Doppler-shifted potential returns.

A GBAD LPI could potentially (again, only POTENTIALLY) reduce the likelihood of an aircraft's RWR or ESM being 'tripped' if an aircraft gets detected, and/or make an ARM attack upon the radar transmitter a little more difficult. In order for this to be achieved, time and funding would need to be expended to develope the appropriate algorithms for the radar's controlling electronics to use. Given how GBAD systems are already vulnerable to ground clutter, and an LPI radar would increase the number of potential return variables which could be discarded as clutter, adding LPI into the mix does not seem like a good idea. Particularly when the IADS systems which could most easily accomodate and use LPI are stationary or semi-stationary units, which are themselves known quantities in that such platforms are not exactly discrete, and would be subject to attack via both ARM and PGM weaponry, whether they are LPI or not.

-Cheers

 

[weasel1962]

Re:

Isn't that why there are 2 kinds of search radar. Standard search radars which don't get affected by ground clutter primarily because it ignores returns below a certain altitude. And separate low level search radars which increases pulse density to overcome ground clutter to ID low flying targets.

In theory one can still use LPI for the former eg tomb stone but is less logical for the latter eg clam shell. Ultimately, even an acquisition radar will still need to go into higher pulse rates if it is to maintain a track on a target and that's when it becomes obvious.

Its not logical to use low power searches as its not going to cover as much airspace. However, in other cases eg pulse compression, side lobe reduction etc, most SAM radars would already employ such techniques to reduce intercept.

Receivers are highly sensitive today. Just think about normal radio comms and its vulnerability to intercept. The amount of radiation is definitely much more for a radar. Even if LPI can ultimately fool a fighter RWR, its not going to fool an ELINT aircraft targeted at such ground emitters.

I think Tod got it absolutely spot on in the the conclusion.

" would be subject to attack via both ARM and PGM weaponry, whether they are LPI or not."

 

[swerve]

How can a PESA be as good as an AESA?

Even a mechanically scanned radar can be better than an AESA. Depends on many factors, but I don't think anyone would claim that a fighter with the Vixen 500E AESA radar has a better radar than a Eurofighter with CAPTOR. The manufacturer certainly doesn't.

 

[SpudmanWP]

Even a mechanically scanned radar can be better than an AESA. Depends on many factors, but I don't think anyone would claim that a fighter with the Vixen 500E AESA radar has a better radar than a Eurofighter with CAPTOR. The manufacturer certainly doesn't.

I was speaking about LPI functions of the radars, not range or raw power.

 

[Feanor]

I would honestly not be so certain that is does have an LPI capability. My doubt stems more from the potential 'value' of LPI radar for GBAD relative to developmental and operational costs than any capability or lack thereof to develop it.

A LPI radar in a LO/VLO aircraft is valuable, because it allows the aircraft to have some measure of sensing/SA via radar, without automatically revealing its presence because it is a radar emitter. The aircraft's radar itself can be LPI through a combination of aircraft speed and frequency-hopping steerable beams. In order for this to be done and also provide/return useful information, a series of potentially complicated algorithms need to be followed, to allow the T/R modules of the AESA to a given vector/volume of airspace while alternating the beams and frequencies used. Part of what can make this so complicated is that as differing frequencies are used, the avionics need to be able to correlate the transmitted signal with the received signal, across the range of frequencies used and their relevant Doppler-shifted potential returns.

A GBAD LPI could potentially (again, only POTENTIALLY) reduce the likelihood of an aircraft's RWR or ESM being 'tripped' if an aircraft gets detected, and/or make an ARM attack upon the radar transmitter a little more difficult. In order for this to be achieved, time and funding would need to be expended to develope the appropriate algorithms for the radar's controlling electronics to use. Given how GBAD systems are already vulnerable to ground clutter, and an LPI radar would increase the number of potential return variables which could be discarded as clutter, adding LPI into the mix does not seem like a good idea. Particularly when the IADS systems which could most easily accomodate and use LPI are stationary or semi-stationary units, which are themselves known quantities in that such platforms are not exactly discrete, and would be subject to attack via both ARM and PGM weaponry, whether they are LPI or not.

-Cheers

Thank you for the explanation. That does make sense.

 

[Todjaeger]

Thank you for the explanation. That does make sense.

Sure thing. I readily admit I do not know for certain that an LPI version is not 'in the works' but given the cost to develop, if one were I would immediately have to ask, "why bother?"

Now, ship-based LPI electronically scanned arrays I do see as being an area of potential development, particularly in light of the amount of ongoing effort for ship sig management.
Of course, a ship at sea only has to be concerned with 'clutter' from high sea states and the radar horizon.

-Cheers

 

[weasel1962]

Re:

Ummm... there are already LPI naval radars in the market.

Example.
http://www.selex-sas.com/EN/Common/files/SELEX_Galileo/Products/SPN730.pdf

In fact most FMCW radars are probably LPI.

 

[weasel1962]

Re:

I was speaking about LPI functions of the radars, not range or raw power.

Then you missed what LPI means.

Examples with an explanation
www.ncc.org.in/download.php?f=NCC2009/file5.pdf

http://www.academypublisher.com/ijrte/vol01/no03/ijrte0103176180.pdf

LPI is achieved by a function of low power, wide bandwidth.

 

[Feanor]

Sure thing. I readily admit I do not know for certain that an LPI version is not 'in the works' but given the cost to develop, if one were I would immediately have to ask, "why bother?"

Now, ship-based LPI electronically scanned arrays I do see as being an area of potential development, particularly in light of the amount of ongoing effort for ship sig management.
Of course, a ship at sea only has to be concerned with 'clutter' from high sea states and the radar horizon.

-Cheers

Given lack of any official claims of such capability, and infact a lack of any meaningful discussion on the subject, my assumption was based more on the fact that the technology in question is not exactly brand new, and the fact that significant efforts were made to use western achievements in electronics to modernize the S-300.

 

[Todjaeger]

Ummm... there are already LPI naval radars in the market.

Example.
http://www.selex-sas.com/EN/Common/files/SELEX_Galileo/Products/SPN730.pdf

In fact most FMCW radars are probably LPI.

This issue with example provided is that it is an I-band navigation radar. While having that be LPI can be helpful, it would not make much difference if the air/surface search radar was not LPI as well. While navigation radars can be used for some search and FC functions, they are not generally used for long ranged or volume searches.

I was thinking of LPI capabilities for radar systems like SMART, Sampson, CEAFAR or AUSPAR. I am not even certain if a SPY-1 array could be given a LPI function, based upon how it operates. Then again, those who do know might very well not be in a position to comment either...

-Cheers

 

[localhost127]

question - are there issues with close-knit formation between multiple LO platforms?

e.g. initial radar signal reflected off and away from LO platform (as designed), but hits adjacent platform (wing man) and reflects back towards the source.

is this an issue at all that is addressed?

 

[Feanor]

question - are there issues with close-knit formation between multiple LO platforms?

e.g. initial radar signal reflected off and away from LO platform (as designed), but hits adjacent platform (wing man) and reflects back towards the source.

is this an issue at all that is addressed?

I'd imagine they wouldn't fly that close.

 

[Todjaeger]

question - are there issues with close-knit formation between multiple LO platforms?

e.g. initial radar signal reflected off and away from LO platform (as designed), but hits adjacent platform (wing man) and reflects back towards the source.

is this an issue at all that is addressed?

AND

I'd imagine they wouldn't fly that close.

With a number of caveats, it could potentially be an issue... Whether or not that is a real concern is likely to be one of those things that those whom actually know are not telling.

One of the caveats has to do with how a particular aircraft manages its radar signature. Some designs (F-117 for instance) manager much of the RCS by arranging for the radar return signal to be directed in a completely different direction from that of the interogating radar transceiver. In such instances, it is conceivable that a redirected radar signal could then be redirected yet again back towards the transceiver. One must note that the usual heading for the re-directed radar signal is usually away from/behind the LO aircraft, which would usually suggest that any redirected signal reflecting off one aircraft to 'paint' another would also be redirected, this time away from/behind the second aircraft.

-Cheers

 

[Abraham Gubler]

Replace "windmills" with "radar" and pretty much summarises this entire thread.

[nomedia="http://www.youtube.com/watch?v=ZQg8JKo_3ZQ&feature=related"]YouTube - Morbo windmill quote[/nomedia]

 

[My2Cents]

AND
With a number of caveats, it could potentially be an issue... Whether or not that is a real concern is likely to be one of those things that those whom actually know are not telling.

The return pulse will be very weak, but more importantly it will be coming from the wrong angle and may be rejected by the radar antenna or processing software as a spurious return. The range and doppler returns on the signal will also be wrong.

 

[localhost127]

didn't want to start a new topic on this question alone --

can a LO platform be designed with a single tail? the reasoning for canted tails is well known - but does this essentially mean that we won't see a single tailed platform that is built around a LO philosophy anytime soon? (e.g. cannot design a single vert-tailed platform that is canted)

 

[My2Cents]

didn't want to start a new topic on this question alone --

can a LO platform be designed with a single tail? the reasoning for canted tails is well known - but does this essentially mean that we won't see a single tailed platform that is built around a LO philosophy anytime soon? (e.g. cannot design a single vert-tailed platform that is canted)

It is critical in stealth designs to avoid 90 degree angles as these form corner reflectors resulting extremely high returns. Since the wings have to be flat a vertical tail will always form a corner reflector.

 

[Aussie Digger]

didn't want to start a new topic on this question alone --

can a LO platform be designed with a single tail? the reasoning for canted tails is well known - but does this essentially mean that we won't see a single tailed platform that is built around a LO philosophy anytime soon? (e.g. cannot design a single vert-tailed platform that is canted)

Ideally, tail-less designs would be built, ala B-2 as this is one way to reduce LO by a significant margin.

Of course aerodynamic issues then present themselves and thus you have a massive compromise already to make such a configuration work, but for LO purposes, tails of any kind are a hindrance not a help...