Stealth Aircraft | Research & Encyclopedia Articles

Stealth Aircraft

The term stealth aircraft was first introduced to the public in the 1980s and 1990s when the United States Air Force allowed a glimpse of the highly classified F-117A fighter and B-1 bomber. However, these aircraft and the cutting-edge technology involved in their design are the culmination of a process that began during World War I.

That war's top fliers understood the importance of spotting the enemy first and attacking before being detected. The most successful strategy involved maneuvering into the universal blind spot--silhouetted against the sun--before attacking. To make their craft less visible in that position, the Germans covered two of their planes--the Fokker E.1 and the Gotha Bomber--with heavy cellophane skins. Unlike conventional canvas coverings, the cellophane allowed sunlight to pass through the plane. This new material, however, failed to hold up under the stress of flying and was soon abandoned.

By the 1930s, aircraft could fly high enough and fast enough to arrive at a target unseen by the human eye, at that time the only means of detection. As a result, only nominal emphasis was placed on stealth design. The one significant exception, however, was the American P-38 Lightning, designed by Lockheed, which was difficult to see, with its smaller side and front profiles.

The development of radar at the beginning of World War II significantly changed air strategy. Airplanes previously invisible to observers could now be sought out and destroyed. To counteract land-based radar, aircraft designers equipped planes with radar of their own and devices to jam or distort enemy signals. Some bombers even dropped chaff, thin metal strips that confused radar and disguised their location. Electronic warfare, as it came to be known, escalated dramatically during the war and following the advent of the jet engine in the 1950s. As a result, aircraft, particularly bombers, grew larger and more complicated. Also, as radar grew more sophisticated and diversified, strike missions became more dangerous and often involved a wide range of aircraft, several of which were exclusively dedicated to creating an electronic smoke screen. By the end of the Vietnam War, the danger and expense of relying on electronic warfare compelled the United States military to seek an alternative. It eventually turned to Lockheed, the company that had designed some of the military's most successful reconnaissance aircraft. During World War II the need for covert flights had become apparent as spy networks proved increasingly inadequate.

In 1952, Air Force Major John Seaberg, an aeronautical engineer, developed a design concept for a spy plane which required that consideration be given not just to performance but to minimizing detectability. With the help of the Central Intelligence Agency, the chief engineer at Lockheed, Clarence L. "Kelly" Johnson, and his design team set about realizing Seaberg's concept, focusing on the radar cross-section (RCS) or detectability of their prototype by radar. The "Skunk Works," as the group became known, eventually produced the U-2. First flown in 1955, the U-2, with its small size, slender profile, and radar-absorbent black paint, proved the value of designing with stealth in mind. Lockheed followed the U-2 with the A-12, which eventually evolved into the SR-71 Blackbird, one of the most distinctive airplanes ever built. Its wing-mounted engines and slim fuselage created a slender side profile, and its smooth body, boasting few straight angles, made it difficult to detect with radar. Designers also used a radar-absorbent plastic material on the wing's leading edges and control surfaces. Despite these advances, however, manned reconnaissance was largely abandoned after the now famous incident in which a U-2 was shot down over the Soviet Union in 1960.

The United States military then turned to spy satellites and unmanned drones. These drones, first developed by the Ryan Aeronautical Company, utilized much of the stealth technology generated by the manned flights. In designing its own drone, the D-21, Lockheed made more extensive use of radar-absorbent and radar-transparent materials and created an extended tail pipe that masked possible infrared trails. Lockheed also developed the manned QT-2 and the YO-3A, both of which produced only minimal engine noise and were used successfully during the Vietnam War.

In an effort to attract the attention of the United States Air Force, Lockheed began to develop a fighter jet that incorporated the technology of the A-12 and the D-21. The Air Force had already allocated some funds to similar research. Leo Windecker, an aircraft designer from Texas, had approached the military as early as 1963 with a proposal for a plane made of a composite material transparent to radar. By the early 1970s Windecker's Eagle had become the Air Force's prototype for stealth research into non-metallic airframes. Lockheed eventually persuaded the military to fund their prototype as well. Officially designated Have Blue, the project was also unofficially referred to as Project Harvey, after the invisible rabbit of the 1950s movie.

The members of Have Blue had to overcome a wide range of obstacles. When in flight, an aircraft is betrayed by many different signals: it puts out infrared radiation due to its warmth, its noise and vibrations send out waves, it absorbs and reflects natural light, and it generates a radar signature whenever a radar beam hits it. Designers countered many of these telltale signs by having the weapons carried internally, burying the engines inside long inlet and exhaust ducts, and avoiding steep vertical slopes, large flat surfaces, and straight lines. To eliminate hot spots picked up by infrared detectors, the exhaust was deflected upward through a series of ports stretching along both sides of the rear fuselage. In addition, more advanced radar-absorbent materials were manufactured and used as the skin of the prototype.

These efforts culminated in the F-117A, finally revealed to the public in 1990, thirteen years after its first flight as a prototype. The F-117A proved its worth in the Persian Gulf War of 1991, when it successfully completed missions against Iraq's most heavily defended targets without suffering damage. The Stealth fighters have also had less fortunate moments in a well-publicized incident, an F-117A broke apart and crashed during an airshow in Maryland in early 1998.

Along with the F-117A, the most advanced stealth aircraft yet designed is the B-2 bomber. Although the government originally considered using Lockheed or Rockwell, which had manufactured the B-1 bomber, it ultimately awarded the contract to Northrop Corporation in 1981, due in large part to that company's Flying Wing project. In designing the Flying Wing, engineers eliminated the fuselage and tail of the craft, leaving a large wing over which the weight of the craft is distributed. Northrop adapted this design for the B-2, effectively hiding the cockpit and engines in the wing. As a result, the almost perfectly flat bomber with its radar-absorbing skin diffracts most incoming radar waves. Its ability to hide from radar becomes obvious in a comparison with the B-52 bomber. The older aircraft echoes about as much radar energy as a minivan, while the B-2 appears more like a butterfly. Although the Air Force requested more than 100 B-2s initially, only 20 were authorized by Congress for construction. The first B-2s entered service in 1993, with several hundred flights logged by 1996. Hoever, the cost of the B-2s (about $2 billion each) has kept the program under constant scrutiny and skepticism since its inception, and it remains unclear if authorization for additional bombed will be granted.