Stealth Secrets

We've all heard about the latest military technology, stealth. What exactly goes into a stealth vehicle? I had the same questions after watching a documentary on one of those cable channels. The documentary left me with more questions than answers, so I once again began searching for knowledge. Most of these answers have now been made available on Wikipedia, but not all- keep on reading.

Iron Ball Paint

What is the secret coating on the F117A? It is called "Iron ball paint". Iron ball is a nickname for carbonyl iron, or iron carbonyl. The molecular structure of carbonyl iron is a single iron atom (valence 10) surrounded by 5 carbon monoxide structures, forming a ball-shaped molecule. What is so special about iron-ball? It absorbs RF energy in the particular wavelength used by primary (search) radar. Iron Carbonyl has been used for years for the core material for RF devices such as toroidal tranformers. It has a similar function as Ferrite, but the spacing of the iron particles (in this case they are atoms) is much smaller. The small size of the particles makes them more useful at smaller wavelengths, higher frequencies. Wikipedia definition says the paint must be "matte black" not entirely true. Iron Ball paint happens to be black because that is the color of the compound. Iron Carbonyl is extremely toxic. So toxic, in fact, that robots are used to paint the F117. There was an incident where a bunch of bats were found dead around a F117A parked in a hanger. They initially thought that the bats couldn't "see" the aircraft with their sonar. I doubt this, because the stealth material is designed specifically to absorb EM energy, and would not necessary be good at absorbing acoustic energy, as they are very different. The bats most likely died as a result of being exposed to the extremely toxic fumes from the Iron Carbonyl.

RCS Definition


One aspect of electromagnetic wave theory deals with what happens when an EM wave hits a transition from one material to another. An example would be the air-aluminum boundary on the surface of a satellite dish. Another would be the interaction between the ground plane of an ILS system. Another would be what happens when a radar signal passes through a radome. There are plenty more, but the one we are concerned with in stealth is the interface between the air and the outer skin of an aircraft. A traditional aluminum aircraft with a rounded body has a terrible (by stealth definitions) Radar Cross Section. It is picked up quite well by a primary radar in all orientations in flight.


A still-classified portion of stealth is Tactics. I believe that these tactics involve approaching a target in a particular sequence of vectors. Some of the factors that go into designing the vectors are: topography, bodies of water, radar locations and type, geometry of the aircraft. In particular, one wants to avoid doing steep banked turns that would expose the underside of the aircraft to the radar. Also, a banked turn towards a radar would expose the intersecting tail surfaces to the radar. Computers model the aircraft and choose the path that would present the smallest possibilty of being detected.

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