광주흥신소 Stealth technology is not a single, stand-alone concept. Instead, it is a collection of design traits, materials, production methods, and combat tactics that all work together to delay radar detection.
Stealth aircraft use rounded shapes and smooth, coated surfaces to reduce radar reflections. Weapons and fuel tanks are recessed in the structure rather than carried as protrusions.
Visual
Aircraft designers have long sought ways to make their machines hard to detect visually. Since the 1930s, they’ve developed technologies to reduce a plane’s radar, acoustic, and visual signatures to make it less visible to enemy air defenses.
Because RADAR technology didn’t exist in World War I, designers focused on reducing aircraft visibility by using clear parts made from plexiglass or other transparent materials instead of the opaque canvas that was standard in that era. They also used colored paint to darken some surfaces.
A surprisingly simple design idea yielded the breakthrough that led to stealth aircraft. In the 1940s, Northrop’s YB-49 flying wing incorporated a large number of curved surfaces that produced a small image on radar screens. A physicist named Pyotr Ufimtsev theorized that a plane’s observable electromagnetic wave return could be predicted based on its shape and surface geometry.
Despite its success, the YB-49 didn’t become operational until 1949. After the YB-49, US government agencies put significant funding into 광주흥신소 developing combat aircraft with low radar signatures, including Lockheed’s manned technology demonstrator Have Blue.
Have Blue was 60 percent smaller than the B-2 bomber that followed it, and incorporated many of the key features of modern stealth aircraft. However, the faceted approach to stealth required sacrifices in aerodynamics and payload capability. Missiles and bombs must be carried internally rather than on wing-mounted pylons, and the absence of afterburners limits speed to subsonic levels.
Acoustic
Stealth focuses on minimizing a number of things that could alert an enemy of an aircraft’s presence. These include reducing the noise an aircraft emits, the heat it produces, and the radiation it sends into the air. The goal is to make the plane virtually invisible and inaudible.
The first stealth-focused aircraft designs were produced between World Wars I and II. At that time, RADAR had yet to be invented, so the main concern was to reduce an aircraft’s visibility. One solution was to sheathe a plane’s wings and fuselage in transparent materials, such as French plexiglass, rather than the opaque canvas that was standard at that time. Interior struts and other parts were painted with light colors to further minimize the aircraft’s optical signature.
During the design process, special care was taken to quiet an airplane’s engines. Instead of the traditional turbojets that use hot exhaust gases to create thrust, stealth fighters and new commercial planes utilize high-bypass turbofan engines that produce the same amount of thrust using a much larger volume of colder air, with far less noise.
Airframe noise is also a significant source of flight sounds, but the continuous molding technology developed for SHARC eliminates flap side-edge noise during aerodynamic tests conducted in the Ames 40-by 80-Foot Wind Tunnel. These tests also demonstrate that the wing trailing edges can be shaped to minimize the aircraft’s sound pressure when it lands.
Infrared
Seeing what humans can’t see is the foundation of stealth technology. Energy in the form of light waves occurs along an electromagnetic spectrum based on wavelength and energy, with visible (light) and infrared being the farthest from visible to human eyes. However, infrared can be sensed by some animals, such as vampire bats, bed bugs, and certain snake and beetle species.
Stealth aircraft design takes advantage of this by using material that is less reflective of infrared, reducing the radar signature. It also involves minimizing the amount of heat released from engine exhaust and other sources, such as air refueling doors and weapon bays. A technique called parallel alignment minimizes radar reflectance by orienting surfaces at the same angle. For example, the leading edges of the wing and tail planes on the F-22A Raptor are set at the same angle.
While the details of how stealth technology works are classified, many aspects can be derived from public documents. Its origins can be traced back to World War II, when German submarines were coated with radar-absorbent material, as well as postwar research into how to make vehicles and weapons invisible to enemy detection systems such as radar and sonar. Those efforts have evolved into the 5th generation of military aircraft, including the F-35 Joint Strike Fighter. ORPE Technologiya, a division of the Russian state-owned corporation Rostec, has been developing a variety of stealth coatings and materials to protect aircraft from radar detection.
Radar
A stealth aircraft is designed to be invisible to radar. It does this by using a combination of designs, materials, and production methods that delay detection. The most effective approach is to reduce the radar cross section of an object or vehicle, which uses RAM coatings and geometry to minimize the reflection of electromagnetic waves back to a radar system.
RADAR works by broadcasting electromagnetic energy in the microwave portion of the radio spectrum and measuring the delay time it takes for echoes to return from objects in the air or landscape. This information is analyzed by computer to identify and characterize targets.
Stealthy aircraft are usually designed with parallel alignments of edges and surfaces, which helps reduce the reflected signal. This is especially important for a strike aircraft that must reach heavily defended enemy sites such as command and control centers or surface-to-air missile (SAM) batteries to attack them. Enemy fire-control radars usually cover these locations with overlapping coverage, so an un-detected strike aircraft must find a gap in the coverage to enter and destroy the target.
Stealth technology has not made it possible to create a completely invisible aircraft, however. Even the most advanced stealth aircraft will leave a thermal and acoustic signature, which can be detected by sensors. For instance, jet aircraft emit thermal emissions as they burn fuel, and Doppler RADAR can detect the swirls of air—called wind vortices—that an aircraft leaves behind it as it travels through the atmosphere.