Editing Stealth technology (section)

==History==
<!--A short history of camouflage needs to be added here too-->
Camouflage to aid or avoid predation predates humanity, and hunters have been using vegetation to conceal themselves, perhaps as long as people have been hunting. The earliest application of camouflage in warfare is impossible to ascertain. Methods for visual concealment in war were documented by [[Sun Tzu]] in his book ''[[The Art of War]]'' in the 5th century BC, and by [[Frontinus]] in his work ''[[Strategemata]]'' in the 1st century AD.<ref>{{Cite journal|last=Wey|first=Adam Leong Kok|date=15 March 2014|title=Principles of Special Operations: Learning from Sun Tzu and Frontinus|journal=Comparative Strategy|volume=33|issue=2|pages=131–144|doi=10.1080/01495933.2014.897119|s2cid=154557121|issn=0149-5933}}</ref>

In England, irregular units of gamekeepers in the 17th century were the first to adopt drab colours (common in 16th century Irish units) as a form of [[camouflage]], following examples from the continent.

During [[World War I]], the Germans experimented with the use of ''Cellon'' ([[Cellulose acetate]]), a transparent covering material, in an attempt to reduce the visibility of military aircraft. Single examples of the [[Fokker E.III]] ''Eindecker'' fighter monoplane, the [[Albatros C.I]] two-seat observation biplane, and the [[Linke-Hofmann R.I]] prototype heavy bomber were covered with ''Cellon''. However, sunlight glinting from the material made the aircraft even more visible. ''Cellon'' was also found to degrade quickly from both sunlight and in-flight temperature changes, so the effort to make transparent aircraft ceased.<ref name="Haddow">{{cite book |last1=Haddow |first1=G.W. |last2=Grosz |first2=Peter M. |title=The German Giants – The German R-Planes 1914–1918 |publisher=Putnam |location=London |year=1988 |edition=3rd |isbn=0-85177-812-7}}</ref>

In 1916, the British modified a small [[SS class airship]] for the purpose of night-time reconnaissance over German lines on the [[Western Front (World War I)|Western Front]]. Fitted with a silenced engine and a black gas bag, the craft was both invisible and inaudible from the ground but several night-time flights over German-held territory produced little useful intelligence and the idea was dropped.<ref>{{cite book |title=The British Airship at War, 1914–1918 |publisher=Terence Dalton |last=Abbott |first=Patrick |year=1989 |pages=31–33 |isbn=0861380738}}</ref>

[[Diffused lighting camouflage]], a shipborne form of [[counter-illumination]] camouflage, was trialled by the [[Royal Canadian Navy]] from 1941 to 1943. The concept was followed up for aircraft by the Americans and the British: in 1945, a [[Grumman Avenger]] aircraft with [[Yehudi lights]] reached {{convert|3000|yd}} from a ship before being sighted. This ability was rendered obsolete by [[radar]].<ref name="NavalMuseumQuebec">{{cite web |url=http://www.navy.forces.gc.ca/navres/10/10-n_eng.asp?category=183&title=1587 |title=Naval Museum of Quebec |work=Diffused Lighting and its use in the Chaleur Bay |publisher=Royal Canadian Navy |access-date=18 September 2012}}{{dead link|date=June 2021|bot=medic}}{{cbignore|bot=medic}}</ref>

[[Chaff (countermeasure)|Chaff]] was invented in Britain and Germany early in World War II as a means to hide aircraft from radar. In effect, chaff acted upon radio waves much as a [[smoke screen]] acted upon visible light.<ref>{{cite book |last=Jones |first=R. V. |date=1978 |title=Most Secret War: British Scientific Intelligence 1939–1945 |publisher=[[Hamish Hamilton]] |location=[[London]] |isbn=0-241-89746-7}}</ref>

The German [[U-boat]] {{GS|U-480||2}} may have been the first stealth submarine. It featured an [[anechoic tile]] rubber coating, one layer of which contained circular air pockets to defeat [[ASDIC]] sonar.<ref>{{cite web |url=http://www.uboataces.com/sonar-coating.shtml |title=U-Boat Anti Sonar Coating |website=Uboataces |access-date=18 September 2012}}</ref> Radar-absorbent paints and materials of rubber and semiconductor composites (codenames: ''Sumpf'', ''Schornsteinfeger'') were used by the Kriegsmarine on submarines in World War II. Tests showed they were effective in reducing radar signatures at both short (centimetres) and long (1.5 metre) wavelengths.<ref>{{cite report |last=Hepcke |first=Gerhard |year=2007 |url=http://www.radarworld.org/radarwar.pdf |title=The Radar War, 1930–1945 |version=English translation by Hannah Liebmann |language=de |publisher=Radar World |page=45 |access-date=1 February 2024}}</ref> The Type 29 concept was the first design to use faceted sides and angled sail were similar to the F-117 stealth fighter but instead of deflecting radar waves, it was intended to deflect active sonar pings from enemy warships.<ref>http://www.hisutton.com/Uboat_XXIXH.html</ref>

In 1956, the U.S. [[Central Intelligence Agency]] (CIA) began attempts to reduce the [[radar cross-section]] (RCS) of the [[Lockheed U-2|U-2]] spy plane. Three systems were developed, Trapeze, a series of wires and [[ferrite bead]]s around the planform of the aircraft, a covering material with PCB circuitry embedded in it, and radar-absorbent paint. These were deployed in the field on the so-called ''dirty birds'' but results were disappointing, the weight and drag increases were not worth any reduction in detection rates. More successful was applying camouflage paint to the originally bare metal aircraft; a deep blue was found to be most effective. The weight of this cost {{cvt|250|ft}} in maximum altitude, but made the aircraft harder for interceptors to see.<ref name="U2+OXCART">{{cite report |last1=Pedlow |first1=Gregory W. |last2=Welzenbach |first2=Donald E. |year=1992 |title=The Central Intelligence Agency and Overhead Reconnaissance: The U-2 and OXCART Programs, 1954–1974 |publisher=Central Intelligence Agency |place=Washington, DC}}</ref>

In 1958, the CIA requested funding for a reconnaissance aircraft to replace the existing U-2 spy planes,<ref>{{cite journal |last=Poteat |first=Gene |year=1998 |title=Stealth, Countermeasures, and ELINT, 1960–1975 |journal=Studies in Intelligence |volume=48 |issue=1 |pages=51–59 |url=http://www.gwu.edu/~nsarchiv/NSAEBB/NSAEBB54/st08.pdf}}</ref> and [[Lockheed Corporation|Lockheed]] secured contractual rights to produce it.<ref name=national/> [[Clarence Johnson|"Kelly" Johnson]] and his team at Lockheed's [[Skunk Works]] were assigned to produce the [[Lockheed A-12|A-12]] (or OXCART), which operated at high altitude of {{cvt|70,000|to|80,000|ft|m}} and speed of {{convert|3.2|Mach|altitude_ft=10,000|mph kph|sigfig=2}} to avoid radar detection. Various plane shapes designed to reduce radar detection were developed in earlier prototypes, named A-1 to A-11. The A-12 included a number of stealthy features including special fuel to reduce the signature of the exhaust plume, canted vertical stabilizers, the use of composite materials in key locations, and the overall finish in radar-absorbent paint.<ref name="U2+OXCART"/>

In 1960, the [[United States Air Force]] (USAF) reduced the radar cross-section of a [[Ryan Firebee|Ryan Q-2C Firebee]] drone. This was achieved through specially designed screens over the air intake, and [[radiation-absorbent material]] on the fuselage, and radar-absorbent paint.<ref>{{cite web |url=https://www.pbs.org/wgbh/nova/spiesfly/uavs_09.html |title=1960s AQM-34 Ryan Firebee (USA) |author=<!--Staff writer(s); no by-line.--> |publisher=[[PBS]] |access-date=14 January 2015}}</ref>

The [[United States Army]] issued a specification in 1968 which called for an [[Surveillance aircraft|observation aircraft]] that would be acoustically undetectable from the ground when flying at an altitude of {{cvt|1500|ft|m}} at night. This resulted in the [[Lockheed YO-3A Quiet Star]], which operated in [[South Vietnam]] from late June 1970 to September 1971.<ref name="YO-3A">{{cite web |url=http://www.vietnamhelicopters.org/yo-3a-quiet-star/ |title=YO-3A "Quiet Star" Silent Stealth Airplane |work=Vietnam Helicopters Museum |access-date=2015-05-02}}</ref>

During the 1970s, the [[U.S. Department of Defense]] launched project [[Lockheed Have Blue]], with the aim of developing a stealth fighter. There was fierce bidding between Lockheed and [[Northrop Corporation|Northrop]] to secure the multibillion-dollar contract. Lockheed incorporated into its bid a text written by the Soviet-Russian physicist [[Pyotr Ufimtsev]] from 1962, titled ''Method of Edge Waves in the Physical Theory of Diffraction'', Soviet Radio, Moscow, 1962. In 1971, this book was translated into English with the same title by the USAF, Foreign Technology Division.<ref>National Air Intelligence Center, Wright-Patterson AFB, OH, 1971. Technical Report AD 733203, Defense Technical Information Center of USA, Cameron Station, Alexandria, VA, 22304-6145, USA</ref> The theory played a critical role in the design of American [[Lockheed F-117 Nighthawk]] and [[Northrop B-2 Spirit]] stealth aircraft.<ref>Browne, M.W. "Two rival designers led the way to stealthy warplanes", ''The New York Times'', Sci. Times Sec., 14 May 1991.</ref><ref>Browne, M.W. "Lockheed credits Soviet theory in design of F-117", Aviation Week Space Technology p. 27, December 1991.</ref><ref>Rich, Ben and L. Janos, ''Skunk Works'', Little Brown, Boston, 1994.</ref> Equations outlined in the paper quantified how a plane's shape would affect its detectability by radar, the RCS.<ref>{{cite book |title=Radar cross section – Second Edition |last1=Knott |first1=E.F. |last2=Shaeffer |first2=J.F. |last3=Tuley |first3=M.T. |year=2004 |publisher=SciTech Publishing |location=Raleigh, North Carolina |isbn=1-891121-25-1 |pages=209–214 |url=https://books.google.com/books?id=0WuGjb8sqCUC&q=ufimtsev+finite+equation&pg=PA210 |access-date=7 October 2009}}</ref> At the time, the Soviet Union did not have [[supercomputer]] capacity to solve these equations for actual designs. This was applied by Lockheed in computer simulation to design a novel shape they called the "Hopeless Diamond", a wordplay on the [[Hope Diamond]], securing contractual rights to produce the F-117 Nighthawk starting in 1975. In 1977, Lockheed produced two 60% scale models under the Have Blue contract. The Have Blue program was a stealth technology demonstrator that lasted from 1976 to 1979. The Northrop Grumman [[Tacit Blue]] also played a part in the development of composite material and curvilinear surfaces, low observables, fly-by-wire, and other stealth technology innovations. The success of Have Blue led the USAF to create the ''Senior Trend'' program which developed the F-117.<ref>{{cite web |url=http://www.f-117a.com/Senior.html |title=F-117A Senior Trend |author=Kevin<!-- Last name not found on website. --> |date=14 July 2003 |website=F-117A: The Black Jet |access-date=2 September 2019}}</ref><ref>{{cite web |url=http://www.vectorsite.net/avf117_1.html#m3 |title=Senior Trend |last=Goebel |first=Greg |website=Vectorsite.net |date=1 March 2010 |archive-url=https://web.archive.org/web/20120103185047/http://www.vectorsite.net/avf117_1.html#m3 |archive-date=3 January 2012 |url-status=usurped |access-date=2 September 2019}}</ref>

In the early 21st century, the proliferation of stealth technology began outside of the United States. Both Russia and China tested their stealth aircraft in 2010. Russia manufactured ten flyable prototypes of the [[Sukhoi Su-57]], while China produced two stealth aircraft, [[Chengdu J-20]] and [[Shenyang FC-31]].<ref>{{cite web|url=https://www.airandspaceforces.com/article/history-of-stealth-from-out-of-the-shadows/ |title=History of Stealth: From Out of the Shadows |website=Air and Space Force Magazine |date=1 September 2019 |first=John T. |last=Correll }}</ref> In 2017, China became the second country in the world to field an operational stealth aircraft, challenging the United States and its Asian allies.<ref name="seidel_2017-10-20">{{cite news |last1=Seidel |first1=Jamie |date=20 October 2017 |title=With the J20 stealth fighter in fully operation service, China leaps ahead in Asian arms race |language=en |work=Australian News |url=http://www.news.com.au/technology/innovation/with-the-j20-stealth-fighter-in-fully-operational-military-service-china-leaps-ahead-in-asian-arms-race/news-story/d5a65bfd8da252a1bb0240026591d575 |url-status=live |archive-url=https://web.archive.org/web/20180226131148/http://www.news.com.au/technology/innovation/with-the-j20-stealth-fighter-in-fully-operational-military-service-china-leaps-ahead-in-asian-arms-race/news-story/d5a65bfd8da252a1bb0240026591d575 |archive-date=26 February 2018}}</ref><ref>{{cite book |last1=The International Institute for Strategic Studies |first1=(IISS) |title=The Military Balance |date=2018 |publisher=Routledge |location=London |isbn=978-1-85743-955-7 |page=5}}</ref>