What is the meaning of the term "stealth" in the context of stealth airplanes?

Invisible aircraft is just a metaphor, the aircraft is equipped with anti-radar system, so that the radar on the ground can not detect (or very difficult) in the sky there is an aircraft flying

Invisible aircraft principle

Invisible for the general public is not strange, although most of these claims come from the novels and myths, but there is no shortage of real-life invisibility examples. Chameleons, for example, are able to become invisible by changing their color. By studying bionics and applying the latest technology and materials, people have finally achieved invisibility in huge airplanes as well.

In principle, the invisibility of a stealth airplane is not invisible to our naked eye, it is designed to make it impossible for radar to detect the presence of the airplane. Stealth aircraft are able to minimize or eliminate useful signals picked up by radar at this stage, although it is one of the most secret military secrets, stealth technology has received great attention from all over the world.

Let's look at the laws that stealth airplanes follow in their design. The two most important technologies for stealth airplanes are shape and materials. First, the shape of a stealth aircraft avoids the use of large, vertical vertical surfaces, preferably concave surfaces, which can make the scattered signals deviate from the radar trying to receive it. For example, the curved fuselage of the SR-71 Blackbird and the B-1 stealth bomber; the flat cockpit cover of the Bell AH-1s Cobra helicopter, which was the first to be used; and the F-117A, which played an important role in the Gulf War. The F-117A, which played an important role in the Gulf War, is a "megatrend" stealth fighter that uses polyhedral technology, and the mission-adaptive wing on the U.S. Boeing F-111 experimental aircraft. The reason why the shape of these airplanes is more eccentric than the general aircraft is that the special shape can accomplish different reflective functions.

Second, stealth airplanes use non-metallic materials or radar-absorbing materials to absorb, rather than reflect, energy from radar. Radar absorbing materials are divided into two categories, one is the resonance type, one is the broadband type. Resonant radar absorbing materials are designed for a certain frequency and are based on magnetic materials that combine phase cancellation interference and attenuation. Broadband radar absorbers are typically made by adding carbon-energy-consuming plastic materials to a matrix such as polyurethane foam, which remains effective over a fairly wide frequency range. Combining radar-absorbing materials with rigid substances through which radar energy can pass creates a radar-absorbing structural material, which is also one of the classified wave-absorbing materials. The use of the latest materials, stealth aircraft on the radar reflected energy can almost do and a sparrow's reflected energy is the same, just through the radar will want to distinguish the stealth aircraft is very difficult.

In addition, should minimize the fuselage's strong reflective points or "bright spots", engine noise, and the body's own thermal radiation, etc., because the existence of these aspects is also easy to "betray" the existence of the aircraft. For example, the SR-71 Blackbird uses a closed-loop cooling system to transfer heat from the fuselage to the fuel, or to dissipate it at frequencies that the atmosphere cannot adequately conduct.

Stealth aircraft play an important role in modern warfare. For example, in the 1991 Gulf War, the U.S. Army sent 42 F-117A stealth fighters, more than 1,300 sorties, dropping about 2,000 tons of bombs, and went on to attack 40 percent of the important strategic targets in only 2 percent of the sorties, with no losses to themselves. With the emergence of materials technology and newer technologies, the stealth aircraft will become more and more invisible and will play an increasingly prominent role in future wars.

There is stealth and there is anti-stealth, and with the continuous understanding of stealth technology, various countries are simultaneously seeking anti-stealth technology. Although the material and shape of the stealth aircraft is very clever, but still inevitably will leave a little trace on the radar. Moreover, the stealth aircraft in order to stealth, sacrificed some other technical performance, such as F-117A this advanced fighter speed is far lower than ordinary fighter, and flight altitude even in the naked eye observation range, so that the ground found to become the enemy of the stealth fighter, and there have been through the ground artillery successfully shot down the F-117A of the war case.

At present, the stealth aircraft from the earliest United States in the 1960s TR-1-type aircraft, the development of the 1990s F-117 "Nighthawk" stealth fighters, F-22-type advanced tactical fighters and the A-12 "Avenger "Navy shipboard stealth attack aircraft, etc., stealth and anti-stealth of the constant battle will make the future aircraft structural design and performance further optimization.

By different roles: stealth bomber (B-2A strategic bomber, B-1B strategic dropout bomber), stealth fighter-bomber (F-117A "Nighthawk" fighter-bomber), stealth fighters (F-22 fighters, JSF multi-purpose fighters, S-37 "Golden Eagles" fighters), stealth reconnaissance aircraft ("Aurora" long-distance manned reconnaissance aircraft, TR-3A "Black Dipper" manned reconnaissance aircraft) stealth reconnaissance aircraft ("Dawn" long-range manned reconnaissance aircraft, TR-3A "Black Dipper" manned reconnaissance aircraft). "Manned Reconnaissance Aircraft"), stealth reconnaissance aircraft (Dark Star unmanned reconnaissance aircraft, "2025 Strike Star" unmanned reconnaissance aircraft).