Stealth technology also known as LOT (Low Observability Technology) is a sub-discipline of military electronic countermeasures which covers a range of techniques used with aircraft, ships, and missiles, in order to make them less visible (ideally invisible) to radar, infrared and other detection methods.
The concept of stealth is not new: being able to operate without giving the enemy knowledge has always been a goal of military technology and techniques. However, as the potency of detection and interception technologies (radar, IRST, surface-to-air missiles, etc.) has increased, so too has the extent to which the design and operation of military vehicles have been affected in response. A ‘stealth’ vehicle will generally have been designed from the outset to have a reduced or controlled signature. It is possible to have varying degrees of stealth. The exact level and nature of stealth embodied in a particular design are determined by the prediction of likely threat capabilities and the balance of other considerations, including the raw unit cost of the system.
The concept behind stealth technology is very simple. As a matter of fact, it is totally the principle of reflection and absorption that makes aircraft “stealthy”. Deflecting the incoming radar waves into another direction and thus reducing the number of waves does this, which returns to the radar. Another concept that is followed is to absorb the incoming radar waves totally and redirect the absorbed electromagnetic energy in another direction. Whatever may be the method used, the level of stealth an aircraft can achieve depends totally on the design and the substance with which it is made of.
Stealth technology (often referred to as “LO”, for “low observability”) is not a single technology but is a combination of technologies that attempt to greatly reduce the distances at which a vehicle can be detected; in particular radar cross-section reductions, but also acoustic, thermal and other aspects.
Radar Absorbing Material: Radar absorbent material (RAM), often as paints, is used especially on the edges of metal surfaces. One such coating, also called iron ball paint, contains tiny spheres coated with carbonyl iron ferrite. Radar waves induce an alternating magnetic field in this material, which leads to the conversion of their energy into heat. Early versions of F-117A planes were covered with neoprene-like tiles with ferrite grains embedded in the polymer matrix, current models have RAM paint applied directly. The paint must be applied by robots because of problems of solvent toxicity and tight tolerances on layer thickness.
Similarly, coating the cockpit canopy with a thin film transparent conductor (vapor-deposited gold or indium tin oxide) helps to reduce the aircraft’s radar profile because radar waves would normally enter the cockpit, and bounce off something random (the inside of the cockpit has a complex shape), and possibly return to the radar, but the conductive coating creates a controlled shape that deflects the incoming radar waves away from the radar. The coating is thin enough that it has no adverse effect on the pilot’s vision.