Stealth technology in the context of "Lockheed F-117 Nighthawk"

The Defense Advanced Research Projects Agency (DARPA) is a research and development agency of the United States Department of Defense responsible for the development of emerging technologies for use by the military. Originally known as the Advanced Research Projects Agency (ARPA), the agency was created on February 7, 1958, by President Dwight D. Eisenhower in response to the Soviet launching of Sputnik 1 in 1957. By collaborating with academia, industry, and government partners, DARPA formulates and executes research and development projects to expand the frontiers of technology and science, often beyond immediate U.S. military requirements. The name of the organization first changed from its founding name, ARPA, to DARPA, in March 1972, changing back to ARPA in February 1993, then reverted to DARPA in March 1996.

The Economist has called DARPA "the agency that shaped the modern world", with technologies like "Moderna's COVID-19 vaccine ... weather satellites, GPS, drones, stealth technology, voice interfaces, the personal computer and the internet on the list of innovations for which DARPA can claim at least partial credit". Its track record of success has inspired governments around the world to launch similar research and development agencies.

The Lockheed SR-71 "Blackbird" is a retired long-range, high-altitude, Mach 3+ strategic reconnaissance aircraft that was developed and manufactured by the American aerospace company Lockheed Corporation. Its nicknames include "Blackbird" and "Habu".

The SR-71 was developed in the 1960s as a black project by Lockheed's Skunk Works division. American aerospace engineer Clarence "Kelly" Johnson was responsible for many of the SR-71's innovative concepts. Its shape was based on the Lockheed A-12, a pioneer in stealth technology with its reduced radar cross section, but the SR-71 was longer and heavier to carry more fuel and a crew of two in tandem cockpits. The SR-71 was revealed to the public in July 1964 and entered service in the United States Air Force (USAF) in January 1966.

Stealth aircraft are designed to avoid detection using a variety of technologies that reduce reflection/emission of radar, infrared, visible light, radio frequency (RF) spectrum, and audio, collectively known as stealth technology. The F-117 Nighthawk was the first operational aircraft explicitly designed around stealth technology. Other examples of stealth aircraft include the B-2 Spirit, the B-21 Raider, the F-22 Raptor, the F-35 Lightning II, the Chengdu J-20, the Shenyang J-35, the Sukhoi Su-57 and the Bayraktar Kızılelma.

While no aircraft is completely invisible to radar, stealth aircraft make it more difficult for conventional radar to detect or track the aircraft effectively, increasing the odds of an aircraft avoiding detection by enemy radar and/or avoiding being successfully targeted by radar guided weapons. Stealth is a combination of passive low observable (LO) features and active emitters such as low-probability-of-intercept radars, radios and laser designators. These are typically combined with operational measures such as carefully planning mission maneuvers to minimize the aircraft's radar cross-section (RCS), since common hard turns or opening bomb bay doors can more than double an otherwise stealthy aircraft's radar return. Stealth is accomplished by using a complex design philosophy to reduce the ability of an opponent's sensors to detect, track, or attack the stealth aircraft. This philosophy takes into account the heat, sound, and other emissions of the aircraft which can also be used to locate it. Sensors are made to reduce the impact of low observable technologies and others have been proposed such as IRST (infrared search and track) systems to detect even reduced heat emissions, long wavelength radars to counter stealth shaping and RAM focused on shorter wavelength radar, or radar setups with multiple emitters to counter stealth shaping. However these have disadvantages compared to traditional radar against non-stealthy aircraft.