The RCS is measured by the microwave tools throúgh experiments,so far there is no such a mathmatic model could acturally caculate a plans RCS which mens you can not know its RCS by look or caculation.Who comments on a plans RCS by look ís either a super smart or super fool.
There is no single equation, ala
grand unified theory in physics, for RCS modeling, prediction, and measurement. But there are four
KNOWN mathematical theories that form the foundation of RCS modeling, prediction, and measurement. Being 'known' meaning they are not state secret by any government but that they are in public domain.
- Radar range
- Edge diffraction
- Surface wave behavior
- Wave superposition
What is state secret is the 'how' when they are exploited in complex relationships to each other in order to work with complex bodies.
Remember...The Russian mathematician Pyotr Ufimtsev was the one who formalized the maths governing edge diffraction, which is only one part of RCS modeling, prediction, and measurement. The behavior of EM signals upon a body was already well known, just that no one was smart enough to mathematically formalize those behaviors. Until Ufimtsev took the time to do it. The Soviet government, in a monumental blunder, dismissed his work as having no military value, allowed his work to be published in the public domain, where it remained obscure until Lockheed engineers got their hands on it. So just because something is in the public domain, that does not mean it is well known. It may be known to some, but not known to some who are missing something in their work.
Lockheed used Ufimtsev's work to model, predict, and finally measured a shape that, even without the 'invisible' hyperbole, was in practice quite 'invisible' to radar, even for today. But the shape could not fly...
Lockheed F-117 Nighthawk - Wikipedia, the free encyclopedia
The F-117 was born after combat experience in the Vietnam War when increasingly sophisticated Soviet surface-to-air missiles (SAMs) downed heavy bomber flights.[12] It was a black project, an ultra-secret program for much of its life, until the late 1980s.[13] The project began in 1975 with a model called the "Hopeless Diamond"...
F-117 History
The model was mounted on a 12-foot high pole, and the radar dish zeroed in from about 1,500 feet away. The site radar operator could not see the model on the radar, until a black bird landed right on top of the Hopeless Diamond. The radar was only picking up the bird....
But in order to make the body flyable, Lockheed must begin to compromise some of that ultra low RCS value. Radars detect birds more by their hard beaks than by their soft bodies. A bird's feather layers are natural RAM that is par with today's manmade RAM.
Rich called on Bill Schroeder, a Lockheed mathematician, and Denys Overholser, a computer scientist, to exploit Ufimtsev's work. They designed a computer program called Echo, which made it possible to design an airplane with flat panels, called facets, which were arranged so as to scatter over 99% of a radar's signal energy "painting" the aircraft.
Basically...Every time an engineer from a subsystem make a modification of his area of expertise, say something like the pitot probe for air data such as airspeed and altitude, the entire virtual aircraft must be plugged back into Echo where the effect of the change is modeled, predicted, and measured to see if the change increased the overall RCS above a specific tolerance. The greater the body, and a wing is much larger than a pitot probe, the longer the re-modeling, prediction, and verification. The work was tedious and keep in mind that this was in the mid-1970s where no engineers below the supervisory level has discretionary access to something called a 'computer'. The final result was the F-117.