gambit
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The most important thing you should keep in mind is that the RCS value is essentially a fictitious value. It is a fiction, not in the sense that it is imaginary like a science fiction novel, but that it can be changed, and how that value changes depends on the relationship between materials and the structural complexity of the body.A slightly unrelated question about composites and RCS reduction. How exactly does using composites reduce the RCS? From the little I know composites are simply transparent to radar. So when we say RCS reduction using composites are we saying that we replace the entire internal structure of a part (lets say the tail) with a composite part? Because a composite skin or some parts of composites will just mean reflections will happen from the internal metal structure.
OR are there radar absorbing composites as well? That would be neat, just replace the skin, keeping the internal structure the same.
In radar detection, the sphere is usually the body of standardization and calibration. The sphere is structurally simple and no matter the approach angle, the radar sees the same RCS value.
FACT: The simpler the structure, the greater the effects of materials on RCS.
What this mean is that a steel sphere will reflects greater than a plastic sphere. What this also mean is that there is a corollary to the above fact: That the more structurally complex the body, the lesser the effects of materials on RCS.
A basic outline of how complex structures affects final RCS is here...
Fundamentals of Stealth Design & Concepts of RCS Reduction | Page 3
It does not mean that if an existing -- or pre 5th gen -- fighter have its skin re-done with EM absorber, the materials will have no effects on final RCS. The materials DO have effects on RCS reduction. The issue is whether the reduction level will have any tactical efficacy at all. Final RCS will decrease, but if the detection range decrease from 100 km to 95 km, it is not financially worthwhile to expend the necessary resources just to gain a mere 5 km advantage, if using the word 'advantage' generously, over the enemy radar.
Tactically speaking, a pilot or a flight should have 30-45 seconds over the enemy in order to re-position himself or re-array the flight into superior combat postures. Unfortunately, that 30-45 seconds time span is rarely achieved when the approaching speed of both sides is in Mach, making that 5 km difference, from non-composite skin to composite skin, pretty much worthless. So the analyses must at least hint at the possibility that any RCS reduction measures onto an existing -- pre 5th gen -- fighter can give the pilot that 30-45 seconds gain, which means the RCS reduction measures should reduce detection range by at least 50%: from 100 km down to 50 km.
Understand that I am playing a bit loose with the numbers since we, or rather I, are treading on the sensitive information line.
Anyway...If your analyses reveals that your proposal cannot give your pilots that tactical advantageous time span to re-position himself and his flight into superior combat postures, whether it is higher altitudes to fire the missiles, or lower altitudes to sneak up on ground targets, then you are essentially wasting your nation's money. It is not a blanket issue. Each fighter platform must be examined individually. Why is it that the US spent money on RCS reduction measures on the F-18 Super Hornet but not on the F-15E ? Maybe somehow the -18's body already have a lower RCS than the -15 so composites on the -18 those RCS reduction measures did give its pilot that time span advantage. Maybe not 30 seconds but only a 20 seconds advantage but the US Navy decided it was tactically worthwhile anyway considering the nature of the Navy's worldwide mission scope.
So while the entire issue can be dissected and isolated into discrete components, financial on one part of the table, tactics on another part of the table, technical feasibility on another part of the table, potential adversary sophistication on another part of the table, etc...etc..., the 'go or no-go' decision on the project rests on all factors.