Stealth technology refers to many techniques used to hide aircraft, ships and other ground vehicles from radar, infrared and other detection systems. This can be done to avoid detection or as a countermeasure.
The secretive United States Military program stealth was created after World War II. The goal of the stealth program was to devise a method that would save aircraft from being bombed or radar-spotted by enemy radar.
Although stealth technologies are classified information, there is some basic information.
Low observability
Stealth design employs a variety of surfaces and coatings that reflect radio waves. They delay their reflection to enemy radars. There are many designs that include smooth or rounded shapes and hidden engines and other devices to reduce reflectivity.
Radar can see aircraft
The first step toward aircraft stealth is to ensure that all parts are as cool as possible. This includes avoiding hot materials like engine exhaust gas and wing surfaces emitting infrared radiation. This radiation is used to target aircraft by heat-seeking missiles or other weapons. It should be kept as low as possible.
Planar shape
The most important stealth technology for aircraft is planar design. It's a simple technique that engineers use to make an aircraft invisible from radar. This reduces its size and radar cross-section.
You can achieve this by designing the aircraft's body with a large surface area to volume ratio, and a small physical cross-section. This helps to reduce radar reflections to a minimum and to improve the aerodynamic efficiency of the aircraft.
Another stealth technology is radar-absorbing materials, also known as RAMs. These materials can be made of a variety of polymers including glass-fiber composites or 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.
RAM can absorb radio energy without creating it. As such, it is typically a thin layer which extends across the entire surface. It is quite thin so it can be difficult to spot, but radar is able to see it.
A RAM material with high RF absorption can greatly reduce the reflected light from a target. This reduces the chance of a target being detected by a radar system that has limited bandwidth or frequency coverage.
Plasma stealth
Plasma stealth is a novel form of stealth. This technology has the advantage of a very narrow beamwidth. Instead of using traditional antennas it uses a series o parallel tubes that are filled up with gas and then energized.
This antenna can send many signals but is only useful when the aircraft is flying at very low speeds. It is currently too expensive to mount a large number of plasma stealth antennas onto military aircraft.