Stealth Aircraft. The term “stealth” is commonly applied to aircraft or missile systems that have been designed to produce as small a radar signature as is practicable. In fact, stealth technology goes beyond this to include reducing as many “observables” of an aircraft or missile system as possible—for example, its visual, noise, and heat signatures, as well as its electromagnetic ones. Stealth technology is applicable to other systems as well, particularly to ship design. Overall, while the term “stealth” is convenient shorthand, a more precise and all‐encompassing term used in the military community is “low observables.”

Interest in reducing the observable characteristics of aircraft dates to World War I, when various of the warring powers experimented with both camouflage paint schemes and even see‐through fabric coatings applied to airplanes. Theoretical studies in World War II indicated that it might be possible to reduce the radar signature of an airplane; in related work, the Germans developed radar‐absorbent materials to shield radar return from submarines' Schnorkels when these retractable air pipes were raised above the surface of the water. Flight tests of flying wing designs in the late 1940's indicated that they had minimal radar return characteristics, but this was serendipitous, and not the result of a deliberate attempt to develop low observable technology. In the late 1950's, with the growing sophistication of radar and missiles, the United States developed a comprehensive series of radar test ranges, where models could be suspended from cables or mounted on poles, and then radiated by radar emitters to assess their “signature” characteristics. Such “pole testing” played an important part in developing both a knowledge base on reducing radar signature and in assessing what portions of an aircraft typically offer the greatest strength of radar return. The strength of return determines the radar cross section (RCS) of the aircraft; it is the apparent size of an aircraft as it appears to search and fire control radars, and has no relationship to the actual physical cross section of an airplane.

The first aircraft designed to have a greatly reduced radar signature was the Lockheed A‐12, the predecessor of the SR‐71 Blackbird strategic reconnaissance airplane. It made use of the three major means of radar cross‐section reduction: shaping, structural absorption via special materials, and specialized coatings. During the Vietnam War, such technology was also exploited on small jet‐propelled drones launched over North Vietnam on photo reconnaissance and electronic intelligence missions during the late 1960's and early 1970's. This experience, coupled with the lessons from the 1973 Arab‐Israeli war (which demonstrated the vulnerability of conventional aircraft to radar‐guided missiles and gunfire, as well as heat‐seeking missiles) greatly encouraged development of larger special‐purpose radar‐defeating “stealth” aircraft.

Ironically, given the Soviet Union's failure to exploit stealth technology, the key breakthrough in developing a stealth airplane came from theoretical studies by Pytor Ufimtsev, the chief scientist at the Moscow Institute of Radio Engineering. Ufimtsev's conclusions, published in the West, were studied by Lockheed engineer Denys Overholser, who recognized that they enabled the systematic analysis of an aircraft's shape to assess its radar reflectivity. Overholser discussed his findings with Ben R. Rich, the chief of Lockheed's famed “Skunk Works” advanced development team. Rich ordered developmental tests and, in September 1975, pole tests on a slender delta configuration having a faceted surface configuration (like a diamond) confirmed that such a shape could have a remarkably reduced radar return. The next step was development of a true airplane.

The first true “stealth” airplane—an aircraft designed primarily to defeat radar–was the Lockheed Have Blue technology demonstrator. Two of these aircraft, first flown in 1977, demonstrated that an aircraft company could design and build a potentially militarily useful airplane incorporating low observable principles. In 1978, the Air Force contracted with Lockheed for a special purpose stealth attack airplane. This airplane, the Lockheed F‐117, first flew on June 18, 1981, entering service with the Air Force in 1983; 59 were subsequently built. During the Persian Gulf War, F‐117's shattered Iraq's air defense control centers, opening up the country to attack by conventional non‐stealthy strike airplanes. Because of their survivability and ability to undertake precision attacks using laser‐guided bombs, they were the only strike aircraft operated over Baghdad throughout the war.

Development of the first stealth aircraft encouraged the development of the Northrop B‐2 stealth bomber (which entered Air Force service in December 1993), and an advanced stealthy cruise missile, the General Dynamics AGM‐129. Stealth is an important development in military aerospace, for it renders an aircraft or missile difficult to detect, and virtually impossible to track, engage, and destroy. The success of these early stealth efforts has spawned interest both in counter‐stealth studies and in a variety of other stealth designs. But as of this writing, only the United States possesses stealth aircraft and missiles in operational service.
[See also Bombs; Fighter Aircraft; Intelligence, Military and Political.]

Richard Hallion