While Eisenhower's scientific advisers on the U-2 and A-12 included Nobel Prize winners, the stealth breakthrough did not came from academic scientists, but, rather, was made by a pair of "computer nerds": Bill Schroeder, a Lockheed mathematician, and Denys Overholser, a Skunk Works programmer. To create a stealth aircraft, Schroeder turned the aircraft design process inside out. Kelly Johnson, in building the U-2, A-12, and D-21, started by designing an aerodynamic shape that could fly, then tried to reduce its RCS. What Schroeder did was to make the conceptual breakthrough that a complex shape such as an airplane could be simplified to a finite set of flat surfaces. In effect, he designed a shape with the smallest possible RCS, then tried to make it fly. Overholser made this possible with a computer program to calculate an airplane's RCS. This was far more efficient in the initial design stage than pole testing a model, and allowed the shape to be modified in the computer.
The result, the "Hopeless Diamond,"with its wings made of flat plates, would never have occurred to an aerodynamicist. To an aerodynamicist, this was heresy.
Airplanes were streamlined; they had curved surfaces. Wings are not made up of flat plates, they had curved surfaces. But this was not about aerodynamics; it was about electrical engineering.
Yet all Schroeder's and Overholser's work would have meant nothing without another technological advance. Despite its strange shape, the Hopeless Diamond was structurally similar to a conventional aircraft. Had the shape been discovered in the 1960s, the basic airframe could have been built, but it would never have flown. The Hopeless Diamond shape was aerodynamically unstable. The aircraft stability control systems which existed in the 1960s, even the one developed for the A-12, could not have coped with the Hopeless Diamond. It was not until the early and mid-1970s that the multi-axis computer control systems necessary for such an unstable vehicle were developed. It was the computer revolution that made stealth a reality; without computers it would not have been possible to calculate the radar cross section of a given shape, or to make it controllable.
By early 1977 two prototype stealth aircraft were being built under the code name "Have Blue." The program had now become the most closely guarded secret since the Manhattan Project of World War II. Despite the loss of both of the Have Blue aircraft during the test program, the RCS test results were phenomenal. Stealth had arrived, and with it a revolution in Air Power.
What then of the future of stealth? Contrary to popular opinion, predicting the future is easy. In the mid-1950s, for example, it was confidently predicted that ballistic missiles would make manned aircraft obsolete. It was also predicted that we would now have flying cars.
The problem is that the political, technical, and social factors which influence the future are so unpredictable as to border on the irrational. Another problem is that we tend to imagine the future as a direct projection of the current moment, rather than looking to the past to see how far we have come and the ongoing trends which have brought us here. To illustrate this point requires a thought experiment.
Imagine for a moment it is the mid-1950s. Forget all that will happen in the next four decades. In the world you know, Eisenhower is President, Elvis is king, both televisions and countermeasures use vacuum tubes, the transistor is still experimental, a computer is a huge mainframe unit which takes up a room, the B-52 is just entering service, airliners use propellers, the launch of the first satellite is still in the future, a manned flight to the Moon is the definition of the impossible, books are written on a typewriter and calculations are done with a slide rule. A technological prophet announces that:
I predict that in forty years, computers will be sold in stores and will be as commonplace as televisions are in the 1950s. These computers will fit on a desktop, while others are small enough to sit in your lap. All these computers are vastly more powerful than any existing 1950s mainframe computer. Many are bought by parents for their children to do homework. Publishers require books to be prepared on these computers; the typewriter is obsolete. These computers are linked together by a communications system called the 'Internet' which allows you to send messages and do research at universities, libraries, and other institutions anywhere in the world.
If this had really been said to a mid-1950s audience of people working in the electronics field, they would have thought the speaker was out of his mind. Yet the technical, political, and social trends that would create the PC were already developing.
Having given this cautionary tale, it has to be said that the future of stealth is a reflection of its past. Have Blue was built with the sole purpose of finding out if stealth would work on a real airplane. Stealth was the only design consideration.
In the design of the F-117 A, the basic Have Blue shape was retained. A few changes were made to correct defects found in the Have Blue, and to accommodate operational equipment. Despite this, in the F-l 17A, stealth superseded other design considerations such as range or payload. It was a short-range, light attack aircraft. With the B-2, the situation is more complex. As with the other early aircraft, stealth came first. However, its stealth capabilities had to accommodate the long range and large payload of a strategic bomber.
Each was a highly specialized, single-mission aircraft. They had also been built under the tight secrecy which enveloped stealth from the late 1970s to the end of the 1980s. The effect of this secrecy was to make stealth a highly specialized concept, one that seemed to apply only to a narrow set of missions, rather than to aerospace technology as a whole. In the decade which followed, and the first combat use of stealth, this changed.
At the end of the 1990s, as this is written, stealth is no longer the first and only design consideration. Rather, it must be balanced with the more traditional requirements of speed, range, payload, weight, maneuverability, and cost. More important, stealth was no longer hidden behind a wall of secrecy. The concept was now integrated into the mainstream of aircraft design, rather than being a separate "Black" aspect. The F-l 17A, B-2 and the F-22 are all openly on display at the annual Edwards AFB air show, as are the stealth UAVs, the GNAT 750, Darkstar, and Global Hawk.
An example of the changing view of stealth is the F-22 fighter. In today's air combat, the preferred method is a first-shot kill with long-range air-to-air missiles.
Historically, most pilots lost in air combat were shot down by planes they never saw. The F-22's stealth features are an extension of this, giving it the ability to destroy an enemy plane, without warning, with a missile fired from miles away. If the ability to make a long-range kill was the only consideration, then a pure stealth design would serve.
In a close-in dogfight, however, a pure stealth-centered design would be at a disadvantage, as it could be slower, underpowered, and much less maneuverable than its conventional opponents. In the case of the F-22, the designers were unwilling to totally compromise its performance in the name of stealth. Several features of the F-22 increase its radar cross section, but that was the price for better maneuverability.
Although the basic shape of the aircraft may be the primary driver of stealth, the design considerations now include existing airframes. An aircraft's RCS can come from relatively small features, such as a gap in an access door. It therefore makes sense that a "clean-up" program, involving discovery and fixing of such reflection sources, as well as addition of Radar Absorbing Material to areas such as intakes, could result in a militarily significant reduction in a plane's RCS. The prime example is the B-IB. This was a redesign of the original B-1A to incorporate a reduced RCS. Subsequently the "Have Glass" program was undertaken in the late 1990s to add stealth features to F-16 fighters. Although this cannot give an F-16 the tiny RCS of a true stealth aircraft such as an F-l 17A or a B-2, Have Glass has made F-16s much more difficult to spot in air-to-air engagements.