Stealth technologies include a range of techniques to obscure radars, infrared detection systems and make ground vehicles (e.g., planes, ships, submarines or missiles) from being detected. Often this is done to avoid detection, but it may also be used as a strategy for countering detection.
After World War II ended, the United States Military started a stealth program. The goal was to develop an effective means of saving aircraft from enemy radar spotting and bombing.
Even though stealth technologies have been classified, we do know some basic information.
Low observability
Stealth designs employ a variety if surface materials and coatings that reflect radio wave reflections, delaying their reflection to an adversary's radar. Some designs have smooth, rounded forms, while others use hidden engines or other devices that reduce reflectivity.
Radar can't see aircraft
The first step toward aircraft stealth is to ensure that all parts are as cool as possible. This means avoiding hot materials such as engine exhaust gases and wing surfaces that emit infrared radiation. Heat-seeking missiles and other weapons zero in on this radiation to target aircraft, so keeping it as low as possible is a critical design objective.
Planar shape
Planar design is the most important stealth technology that an aircraft can use. This simple technique allows engineers to hide an aircraft from radar by reducing its size and cross-section.
This is possible by designing an aircraft's structure to have a high ratio of surface area to volume and a low cross-section. This reduces radar reflections and improves aerodynamic efficiency.
Another stealthy technology is radar absorption materials, or RAMs. These materials can be made from a number of different polymers, including glass-fiber composites and multi-walled carbon nanotubes.
Radar absorbing material can be applied directly to the aircraft's surface, or it can be embedded within a structure. The latter is much more common and has many advantages.
The RAM absorbs radar energy and does not generate it. It is often a thin layer that covers the entire aircraft's surface. Although it is thin, it can be difficult for radar to detect.
An effective RAM material can absorb a large amount of RF energy, so it can greatly reduce the reflected signal from a target. This lowers the chances of a target being identified by radar systems with limited frequency and bandwidth.
Plasma stealth
Plasma stealth is a novel form of stealth. This technology has a narrow beam width, which is the main advantage. It is not like traditional antennas. Instead, it uses a series of parallel tubes which are filled with gas. Then they are energized.
Although this type of antenna can transmit a large number of signals, it is not effective when an aircraft is flying at subsonic speeds. It is currently too expensive to mount a large number of plasma stealth antennas onto military aircraft.