Stealth Tech: Physics or Electronics?

[EngTechno]

I am strongly interested in Stealth Technology. Is this field concerned with Physics? What subject do I need to study for this Technology? Plasma or Electronics?

 

[Gokul43201]

Stealth is achieved mostly through the use of a polymer coating that is a near perfect absober in typical radar wavelengths. Another aspect in stealth design is the geometry of the aircraft (minimizing normal surfaces). And finally there is radar jamming - which, I don't believe gets used by a stealth fighter/bomber - but rather by a different aircraft (like an EA-6B Prowler) when shielding a squadron.

The field is definitely related to physics. I would describe it as interdisciplinary; involving Physics/Electromagnetics, Materials Science and Electronics.

 

[Cap'n Refsmmat]

Geometry for one, because shape is important. Things like right angles entirely ruin it. The surface has to be designed to almost always reflect the transmission away from the transmitter/reciever.

 

[Ian]

The easiest way to develop stealth technology is to examine the refractive index of the materials used. Radar is an electromagnetic wave and materials will respond to it in the same manner as they do to visible light. The only difference is a change of wavelength between visible and microwave radiation.

 

[Njorl]

There is also the matter of emmissions. These take two forms, thermal, from the engines and exhaust, and electrical, from the on-board electronic systems. Electrical emissions can also be caused by aircraft picking up static charge, but I don't think anyone can use that for detection - yet.

Njorl

 

[Gokul43201]

Oh yes, exhaust temperature control is a big part of the B2's design.

 

[Moe]

In stealth aircraft, RAM and RAS are used. The first are Radar-Absorbing Materials, which are polymers that absorb most of the radar energy. RAS are Radar-Absorbing Structures, a honeycomb-type structure that essentially "traps" radar waves.

Next, you try to either use weird angles (F-117) to scatter the radar energy all over the place and to make sure that as little as possible gets back to the emitter. Or you use an approach similar to that of the B-2 and F-22: a small profile, no vertical stabilizers (B-2) or angled ones (F-22).

IR stealth is achieved by IR-absorbing coating and by trying to mask the engine heat signature. You will notice that the engine nozzles in both the B-2 and the F-22 are not on the very rear of the aircraft. That is to give the hot air a chance to mix with the surrounding cooler air and to therefore cool it down. There are also designs which inject a coolant into the airstream after it has left the nozzles to further cool it down.

Jamming is not a form of stealth. If a EA-6 turns on its jammers, everyone will know it is there - they just can't get a lock on it, or talk to each other for that matter. Stealth is akin to walking around at night with a black ninja dress, jamming would be carrying a huge spotlight and shining it in peoples eyes.

Interesting sidenote: The canopy of the F-22s cockpit has a thing layer of gold on it to keep emissions from entering or leaving the cockpit.

 

[kuengb]

Talking about gold: I've read once that one of those stealth bombers (don't know their names) is more expensive than its own weight in gold :surprise:

So you can't see them with a radar, hm? No problem, my good old dowsing rod will do the job. No aircraft engineer can beat that

 

[russ_watters]

A good book for an engineer's perspective is "Skunk Works" by its director Ben Rich. It cronicles the development of stealth.

Stealth is predominantly based on geometry. The concept came from a Russian scientist who derived from Maxwell's equations a method for calculating the reflectivity of a flat panel. A Lockheed engineer read the paper and developed software for calculating radar cross sections of objects composed entirely of triangles. Hence, the F-117's shape.

The B-2 uses similar software, but more powerful computers means more complex shapes. Plus, the skin in some places is transparent, with faceted surfaces underneath.

Absorption is important, but not anywhere near as important as geometry.

To get into it, electrical engineering, physics, computers, materials, all good fields of study.

 

[Moe]

The faceted surfaces would be RAS. By the way, there have been attempts at detecting those stealth aircraft by linking multiple receivers together, each receives a little bit of the scattered radar energy, and then the position of the aircraft is triangulated. It's pretty tricky to do that, though.

Russ: The book you mentioned, for what kind of reader is it intended? That is, would I have to know something special about e.g. engineering to understand it, or is it written for the "general public"?