What Are Stealth Aircraft?
Stealth aircraft are designed to remain undetected by using a variety of technologies that reduce the reflection/emission of radar, infrared, visible light, radio frequency, and audio, all of which are under the umbrella of stealth technology. Stealth technology, or low observable technology, is a subdiscipline of military tactics and passive and active electronic countermeasures that cover a wide range of methods used to make aircraft, ships, missiles, and other vehicles or weapons less visible to radar, infrared, sonar, and other various detection methods.
The F-117 Nighthawk served as a notable example of the first operational aircraft with stealth technology. Other famous examples include the B-2 Spirit, the F-22 Raptor, the F-35 Lightning II, the Chengdu J-20, and the Sukhoi Su-57. While an aircraft has not been devised to be completely invisible to radar, stealth aircraft are not easily detected or tracked by conventional radar, allowing them to avoid being targeted by radar guided weapons.
What Is Stealth Technology?
Stealth technology combines passive low observable (LO) features with active emitters like low-probability-of-intercept radars, radios, and laser designators. Generally, they are used alongside active measures to minimize the aircraft’s radar cross section as common actions such as hard turns can double the aircraft’s radar return. This is accomplished by utilizing a complex design philosophy to reduce the ability of an opponent’s sensors to detect, track, or attack the stealth aircraft. More than that, this philosophy accounts for heat, sound, and other emissions of the aircraft, which are other factors that can be used to locate it. Sensors used for such technology are made to reduce the impact of current LO technologies, some of which include IRST (infrared search and track) systems, long wavelength radars, RAM, or radar setups with multiple emitters to counter stealth shaping.
Stealth Aircraft Background
During WWI, the Germans experimented with cellulose acetate (Cellon), a transparent covering material, in an attempt to reduce the visibility of military aircraft. For example, the Fokker E. III Eindecker fighter monoplane, the Albatros C.I two-seat observation biplane, and the Linke-Hofmann R.I prototype heavy bomber took advantage of Cellon; however, over time, it proved ineffective and counterproductive. This is because the sunlight would hit the Cellon covering, making the aircraft even more visible. Furthermore, the material would degrade rapidly due to excess sunlight or inflight temperature changes.
By 1916, the British would launch a small SS class airship crafted for night-time aerial reconnaissance over German lines on the Western Front. It was equipped with a silenced engine and a black gas bag, and it could be invisible and inaudible from the ground. Shortly after, the idea behind this airship would be rendered useless as it produced little useful intelligence.
Nearly three decades later, the Horten Ho 229 flying wing fighter-bomber was developed in Nazi Germany during the last few years of WWII, and it had some stealth characterisitcs. Tests by the Northrop-Grumman Corporation later established that the aircraft’s shape would have made it virtually invisible to the top-end High Frequency band and 20–30 MHz primary signals of Britain's Chain Home early warning radar, given that the aircraft was traveling at high speed. Despite this, the Ho 229 was never intended to be a stealth aircraft.
Modern Day Stealth Aircraft
The success of modern stealth aircraft can be traced to Soviet scientist Petr Ufimtsev’s computer program called Echo I. Launched during the 1970s, Echo made it possible to predict the radar signature of an aircraft constructed with flat panels, or facets. In 1975, Lockheed ADP engineers found that an aircraft made with faceted surfaces could potentially have low radar signature due to the surfaces radiating all the radar energy away from the receiver. Later, Lockheed would build upon the concept and the Lockheed Have Blue, nicknamed “the Hopeless Diamond,” would be born. This aircraft would lay the foundation for future engineers to devise prototypes that could be virtually invisible.
A truly stealthy design was achieved with Lockheed’s F-22. Its design disguised its infrared emissions, making it hard to detect it by infrared homing surface-to-air or air-to-air missiles. The F-22 also addresses common problems with other aircraft like getting a grip on radio transmissions and noise abatement. By December of 1989, the first combat use of purpose-designed stealth aircraft was seen during Operation Just Cause in Panama, where two US Air Force F-117s bombed a Panamanian Defense Force barrracks in Rio Hato, Panama. By 1991, the success of this operation led to the incorporation of F-117s during the opening phase of Operation Desert Storm in Iraq.
Throughout the history of stealth aircraft, the US and Israel are thus far the only countries that have actively used them in combat. One of the most famous uses by the US includes the May 2011 operation to kill Osama bin Laden. From the wreckage that took place during the attack, it was revealed that the helicopter that crashed in the bin Laden compound had stealth characteristics. This became the first publicly known operational use of a stealth helicopter. Since then, stealth aircraft have proved to be incredible assets, with Chinese, Israeli, and US variations making appearances over the last decade.
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