MigLThanks Pfcem, but i don’t think some people on this board will bother going to you links and reading them, because they’ve convinced themselves they already know all about stealth.
It is nowhere near an exact science that can be solved with a few simple equations, but must be solved by numerical methods, ie. successive approximation, because of real world complexity. Even the approximate solutions have to be re-checked using anaechoic chambers and radar test stands.
MigLTo KKM57P, where did you get the two equations to calculate RCS?
The first, for 3D is completely useless as it doesn’t define what Ss and Si are, all it tells us is that RCS isproportional to the limiting value of the ratio of the two values as the radius (distance ??) approaches infinity.
The second for a 2D object is much easier to dismantle. It tells us the RCS of a flat plate of area A is proportional to the square of the area and inversely proportional to the square of the wavelength. HOWEVER, this does not take into account edge effects, as radar acts like a wave and all sorts of interesting things happen at discontinuities, nor does it take into account material composition; will a 1ft square piece of styrofoam have the same radar return as a 1ft square piece of metal? I think NOT.
Its very easy to look up equations in some technical paper where they may be used to compare radar returns of two similar objects where only the size is different, or some other idealised conditions, but I don’t think you have a clue as to their meaning. You’re not impressing anyone
MigLIf an interceptor is illuminating the target for the semi-active missile then the interceptor can ‘see’ the target with his radar and so the target is not stealthy. If the interceptor cannot see the stealthy target then what exactly is he illuminating for the guidance system of the missile to pick up????
Yes, mass-energy is conserved, I do have a degree in Physics, however it can be converted to other forms and still satisfy this law. The amount of heat produced by absorbing radar waves at say 25km, would not increase the temperature by even one degree as intensity falls off exponentially.
MigLAnd another thing, greater parallax does not increase received signal strength, it only increases the resolution of the signal.
MigLYou do realise that the reflection lobes from a plane-alignment stealth aircraft are designed to emit at angles >10 degrees, so that if the missile is flying an intercept course it will never actually see this return. Also you have to have seen the aircraft in the first place to fire a separate transmitter/receiver equipped missile at it. As far as I know there are no
fighters equipped with “bi-static” radars.
By the way you get way more angular displacement in one second of flight than you would by separating transmitting antenna and receiving antenna by several hundred feet, so I don’t see the advantage of so called bi-stati radar.
MigLAlways the squabbling about definitions!!
Instead of picking up a dictionaryto look up the definition of a fighter, Pfcem, do some research on the history of the F-35 and how it evolved to JSF from JAST and from CALF. The requirement was for an affordable attack aircraft which could deliver ordinance with impunity, through the use of stealth and an excellent ability to defend itself with fighter-like qualities. I would say LM succeded in meeting all the requirements except, by all estimates, affordability.
Just because the job of a modern fighter has changed to include attack abilities does not mean all attackers are now fighters.
MigLSferrin, Harry Hillaker died just last year. More importantly he retired from his position at General Dynamics in 1985, well after GD’s submission to ATF had been finalised (there was a picture in a much earlier post), and then rolled into, along with Boeing’s submission into the Lockheed design, which at the time looked vastly different. He was, after retirement, a consultant to Lockheed-Martin once they bought GD’s aircraft division, well into the 90s, and so had some input into JSF also.
To intercept an F-111, first you need to know that its coming. If your ground based radar doesen’t know its coming or the direction, then no interceptors are scrambled. That is the whole point of flying nap of the earth. No other aircraft does it better! And yes, it can sustain M1.25 at 200ft for a considerable time. Low and fast was US strike doctrine for 40yrs, they don’t need it anymore because they have VLO and air dominance.
All the people who have a little knoledge about stealth constantly spout off about the few things they know. Intakes have to be serpentine so radar dosen’t see the metallic compressor blades? That is one solution, there are others which PAK-FA might be using, so we cannot assume that its intakes aren’t stealthy. Does no one remember the x-32? It had a huge gaping intake, yet it was judged to be as stealthy as the x-35. It did not lose the JSF competition for lack of stealth. Exhausts on the other hand, are a different matter, and a gaping hole with visibe turbines will always give a good radar return, but so will 1700 degrees to an IR seeker. The difference is a chasing missile will always be in a lower energy position than a head-on missile and so provides the target some extra options which a designer may be able to live with.
MigLA stable tailed aircraft has the centre of lift behind the centre of gravity and the tailplane has to provide downward force to rotate or pitch the aircraft. We increase pitch response as well as total lift by making the aircraft unstable, the F-16 for example, by moving the centre of lift foreward and ahead of the centre of gravity so that the biggest control surface, the main wing provides the pitching moment and the tailplane controls it with upward lift.
Similarily early canard configurations were stable, with the centre of lift behind the centre of gravity, so that the foreplanes on the Viggen provided upward lift. The Typhoon is unstable so that the main wing provides a large pitching moment, CoL ahead of CoG, and the foreplane controls the pitch with downward lift.
MigLRedreidy, this is totally unrelated, but I don’t believe there is any aircraft that can run down an F-111, at LOW LEVEL. The tyfoon or any other plane with such a large wing would give their pilots kidney damage from all the buffetting at M1.25 and 200ft. It’s been said a dozen F-111, flying at M1.25 and 200ft, over a heavily populated area (like Bhagdad), could do more damage due the sonic booms than if they dropped their full compliment of forty-eight 500lb bombs each.
MigLSorry meant Hilliker in previous post (maybe spelled HillAker, I don’t recall).
Djcross, re-rdiated EM waves are only possible if the composition material has “loose” electrons in the conduction band of its atomic/molecular structure. To act like an antenna, it has to be metallic!
If the foreplane is made entirely out of dielectric material, like most composites, without a metallic inner structure (I’m assuming that’s a stretch with today’s composite technology although I could be wrong and there may already be flying examples),then it would be, for all intents and purposes, transparent and non-reflective, ie. invisible.
In such a case a foreplane, or taiplane would add absolutely nothing to the aircraft’s RCS.
But back to generations. The reason I’m against using the term is because after close to a dozen pages of discussion, we cannot agree on a valid usage. It just tends to confuse the issue of an aircraft’s abilities. Instead of saying this plane is better because of agility/stealth/cruise speed/TO distance/radar or any other quantifiable aspect, we say it’s better because it’s 5th gen as opposed to 4th. An example would be saying F-35 is better than Tyfoon because it is a later generation, but if the customer needs an interceptor/air superiority plane, I would think the capabilities of the Tyfoon would be more desirable.
Lets discuss a plane’s abilities as they relate to a mission/requirement, not wether it can be pigeon-holed into a specific (but not unanimous) generation.
MigLPrior Lancey,
the quote you attribute to a general was actually made by the chief designer of the F-16 of the Fort Worth division of General Dynamics, now Lockheed-Martin. His name is Hillier, I believe, and he is still the chief designer there, having worked on the F-22 and F-35.
It’s been mentioned that the original submission by Lockheed to JAST, or was it still CALF in the early 90s, was a canard design, which was then discarded. It was only discarded when Lockheed gained access to the engineers of the former Convair or GD ft. Worth division. It was also discarded after the Navy came on board and it became JSF, because the Navy requires planes that land with a flat attitude for carrier ops, and canards or deltas don’t as they need a high pitch landing attitude. You’ll remember that the Boeing submission to JSF changed at the last minute from a delta to swept wing with tailplane for just that reason.
MigLThe US’s first steps towards stealth were the Lockheed Have Blue and the Northrup Programme which looked like a whale ( I’m at work so I don’t have the programme name at hand, should have looked it up before writing this post ) Lockheed’s had highly swept or tapered delta wings and IIRC Northrup had straight tapered wings, in the 1980s.
According to Sferrin’s logic, there had been no trapezoidal winged (YF-23) stealth aircraft, no delta winged (X-32) stealth aircraft and no canard winged stealth aircraft because they are incompatible with stealth when in reality they just had not been designed yet.
I think Sferrin is just trying to prove a point. How little he actually knows about stealth technology.
MigLHey Sferrin, we’ve had this discussion before, regarding foreplanes on stealth aircraft, and didn’t come to a conclusion then either. The US DoD has always been a conservative bunch. On a related topic, the reason the YF-23 wasn’t chosen over the YF-22 was because it was a higher risk design, the YF-22 was lower risk, not because of agility or stealth or other factors. It was simply a more risky developement, and they’ve done this many times over the years with several programmes.
So, its not that they can’t develop canard configured stealth, or are afraid, they just prefer to stick with the tried and true, ie. don’t take unnecessary risks.
MigLWhen was the last time the US fielded a canard configured aircraft. That’s right, never! And since the US is the only country with all-aspect stealth aircraft, that is the reason there are no stealthy canards. Not because they are incompatible. The US has an aversion to canard designs for reasons which may or may not be valid. I think as more stealth designs are introduced you will start seeing foreplanes on them.
MigLRCS=size of marble?
RCS=size of golf ball?
Look, even disregarding all other effcts on an incident EM wave, such as diffraction, refraction, re-transmission, etc. the strength of the reflection is dependant on the frequency (or wavelength, as they are inversely proportional and related by c) of the incident radiation. For example, a black marble will absorb visible radiation while a white marble will reflect a lot more of it. If both are placed against a non radiating background (black), I will spot the white one at a much greater distance. If we now use infra-red to look for the black and white marbles, and assuming they are at equal temperatures, I will spot them at similar distances.
So, an RCS the size of a marble, or a golf ball, or a hot air balloon for that matter, means absolutely nothing unless the conditions such as temperature and frequency (incident, reflected and scanning as there are cases when they can differ) are specified.
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