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Palnatoke

Banned Member
I am interested in how the "game" of Radars vs. Stealth is developing.

Specifically I would like to use it to get a better understanding of the importance of VLO objects in millitary applications - and those objects that are not VLO.

Are f.ex. the F18, eurofighter, Raf or gripen made obsolete by not being VLO?

Can a VLO anti ship missile, with a highish degree of probability slip undetected through the defense around a ship, and hence render larger surface combattants , well, obsolete?

How stealthy can you make a ship - say a frigate?

How effective are modern radars? Do they attain sufficient ressolution at sufficient ranges to detect these VLO objects in time? I think specifically on AESA types of radars.

How does the, I think it's called, frequvency agility of these AESA radars affect the stealth properties of the VLO object? I am thinking that the object should look different, in different wavelengths/frequvencies. A follow up question is, how agile are these radars, in which spectrum can they emit electromagnetic radiation?


As I understand the math/physics, the AESA radars are "low probability of intercept", where "Low" should be read as "unlikely".

Is the following scenario realistic:
A VLO object f.ex. an air plane or ship achives 100% advantage on a non-VLO object, by remaining undetected while using it's ASEA radar to scan the non-VLO object that can't intercept let alone know that it is being scanned?

Can the technology behind AESA radars be used to devise radars of practical dimensions that operate in f.ex. the near meter bands, and can modern DSP (digital signal processing) be used to make such long wave radars effective (that'll be sufficiently surpressing the noise in that region of EM). If so, can that technology be used to completely negate most current stealth (Ie. that an object which is VLO in the, say, millimeter band isn't VLO in the, say, meter band) .

any input would be greatly appreciated.
 
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Palnatoke

Banned Member
  • Thread Starter Thread Starter
  • #2
Well since nobody honors me with a reply, I can might as well talk to my self... :(


LO, RCS and detection range.


Simplistically you can view a radar viewing an object the following way;

A radar emits a signal or pluse, with a given power, we will assume that the radar does this uniformly in all directions.
The power of this signal will then decrease as R (range/distance) squared. (You uniformly distribute the power across the surface of the sphere with radius R)

A portion of this signal is then incident on an object, O, which will then emit that power as if it were a transmitter, a portion of this signal will then reach the initial radar as a radar echo.
This Echo also decreases as R squared.

this leads (together with other stuff) to the Radar equation, which, if we simplify a lot , is

Pr=constant*RCS*Pt/R^4

Pr is power recived, Pt is power transmitted, RCS is the radar cross section of the object, R is the range/distance to the object. We will assume that transmitter and reciever has the same location.
In reality the above constant is not a constant and is depending on the radar, enviroment and other stuff which we, for the sake of simplicity, will just collect in a single constant.
Notice that the R^4 dependence is due to the signal first travelling to the object, which then emits a new signal that has to travel back (to the antenna).

Let's imagine the following scenario: We have a radar that's viewing two objects, O1 and O2, these objects have different RCS (respectively RCS1 and RCS2) and different range to the radar. Let's for fun sake say that O2 has a RCS in the interval [0.001*RCS1, 0.01*RCS1].

Let's say that the extreame range at which our radar can detect object O1 is R1. We can then use the above to deduce that this radar should be able to detect, everything else equal, object O2 in the range interval [0.18*R1,0.32*R1].. in words; object O2 can stay undetected within 18-32% of the range that O1 is detected at.

From what I have been able to dig out; The Eurofighter is reported to have an RCS of about 1 square meter. The F117 is reported to have an RCS in the interval 0.001 to 0.01 square meters.
The above will thus suggest that if you have a radar that can detect the EF at, say 100 Km, this radar will, everything else equal, detect the F117 at a range between 18 and 32 Km.
 
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PhysicsMan

Member
Palnatoke said:
Well since nobody honors me with a reply, I can might as well talk to my self... :(


LO, RCS and detection range.


Simplistically you can view a radar viewing an object the following way;

A radar emits a signal or pluse, with a given power, we will assume that the radar does this uniformly in all directions.
The power of this signal will then decrease as R (range/distance) squared. (You uniformly distribute the power across the surface of the sphere with radius R)

A portion of this signal is then incident on an object, O, which will then emit that power as if it were a transmitter, a portion of this signal will then reach the initial radar as a radar echo.
This Echo also decreases as R squared.

this leads (together with other stuff) to the Radar equation, which, if we simplify a lot , is

Pr=constant*RCS*Pt/R^4

Pr is power recived, Pt is power transmitted, RCS is the radar cross section of the object, R is the range/distance to the object. We will assume that transmitter and reciever has the same location.
In reality the above constant is not a constant and is depending on the radar, enviroment and other stuff which we, for the sake of simplicity, will just collect in a single constant.
Notice that the R^4 dependence is due to the signal first travelling to the object, which then emits a new signal that has to travel back (to the antenna).

Let's imagine the following scenario: We have a radar that's viewing two objects, O1 and O2, these objects have different RCS (respectively RCS1 and RCS2) and different range to the radar. Let's for fun sake say that O2 has a RCS in the interval [0.001*RCS1, 0.01*RCS1].

Let's say that the extreame range at which our radar can detect object O1 is R1. We can then use the above to deduce that this radar should be able to detect, everything else equal, object O2 in the range interval [0.18*R1,0.32*R1].. in words; object O2 can stay undetected within 18-32% of the range that O1 is detected at.

From what I have been able to dig out; The Eurofighter is reported to have an RCS of about 1 square meter. The F117 is reported to have an RCS in the interval 0.001 to 0.01 square meters.
The above will thus suggest that if you have a radar that can detect the EF at, say 100 Km, this radar will, everything else equal, detect the F117 at a range between 18 and 32 Km.
Click to expand...
One note on signal's range dependence: it doesn't scale as 1/R^4, it should scale as 1/(2R)^2. That will change your numbers significantly.
 
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Palnatoke

Banned Member
  • Thread Starter Thread Starter
  • #5
yeah, one easely forgets that the signal has to travel back, after being "re-layed".
 
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