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Centennial of Aviation


The Evolution of Military Aviation

In the twenty-first century, we will see the dawn of the space fleet.

In the 100th year of powered manned flight, it is appropriate that we step back and review the evolution of military aviation and look ahead to the future. How did the United States achieve its current dominance in the air? I believe many factors have played a role - innovations by aerospace engineers from many nations, the visionary ideas of a few individuals, and the means (and willingness) to spend significant portions of our wealth on military equipment. America was founded by people seeking to distance themselves from relatively static societies, people attracted to building a new land and developing a new society. The spirit of these individuals, as embodied in America’s engineers, is largely responsible for our success as a nation and particularly for our success as aviation innovators.

Throughout the nineteenth century and the continuing Industrial Revolution, great strides were made in engineering, medicine, physics, chemistry, and other scientific fields. Man’s horizons were expanded again and again, but one of the greatest challenges of all - the ability to fly - remained a challenge. In the twentieth century, no greater progress was achieved than in aviation (with the possible exception of the rise of electronic systems).

Think of it. A little more than 10 years after the first powered flight by the Wright brothers in 1903, there was dogfighting over Europe; 20 years later, commercial aviation began; 30 years later, there were routine passenger flights; 40 years later, jet aircraft; 44 years later, level, supersonic flight; 50 years later, the possibility of atomic powered aircraft; 60 years later, Mach 3 planes; and 70 years later, the Concorde.

Behind these achievements stand pioneers of military aviation, such as Orville and Wilbur Wright, Giulio Douhet, Billy Mitchell, Manfred Von Richtoffen, Willy Messerschmidt, Ernst Heinkel, Artem Mikoyen and Mikhail Guerevitch (MiG), Eddie Rickenbacker, James Doolittle, Glenn Curtiss, William Boeing, Leroy Grumman, Igor Sikorsky, Kelly Johnson, Chuck Yeager, Scott Crossfield, Pete Knight, Harry Hillaker, and a multitude of others whose names we do not know. These aviators and engineers of the past have provided the basis for where aviation is today and where it can go in the future. Each nation can determine its own aviation destiny. In the case of the United States, we have reached a fundamental decision point on the vector for future military aviation, and moving forward will require all of the engineering skills we have developed over the past century.

The War Years
By World War I, aviation enthusiasts here and abroad had become convinced that the refinement of airplanes would lead to greatly advanced military capabilities. At first, airplanes merely provided a vertical battlefield perspective, replacing the balloons that had been used for this purpose since the American Civil War. When the enemy began to counter this advantage, aircraft were armed, air battles ensued, and dogfighting tactics were developed. The regular Army was not impressed, however, maintaining that aviation was peripheral to the serious business of ground warfare.

In the 1920s, General Billy Mitchell demonstrated the vulnerability of the naval fleet to attack from the air and was rewarded with a court martial and an ignominious end to his career. In the 1930s, America and the rest of the world slumbered while Goering, with Hitler’s support and approval, built the German air fleet.

World War II was the supreme wakeup call. At the outset of the war, U.S. Army and Navy aircraft were inferior in almost every way to German and Japanese aircraft. But thanks to innovative engineers, by the later stages of the war, our aircraft were significantly superior to those of our adversaries. We also learned to use our admittedly inferior machines to advantage.
Billy Mitchell was vindicated by the battle of Midway, which changed the course of the war in the Pacific, when Japan’s offensive naval superiority, embodied by aircraft carriers, was destroyed by American naval dive bombers, all technically inferior to the Japanese Zero. British and American bomber fleets also had a significant effect on the progress of the war in Europe. These lumbering aircraft developed new covering formations to protect against Luftwaffe fighters; to fall out of formation was to be fatally exposed.

The concept of close air support of land forces, developed by the Germans and the Russians, greatly increased the capabilities of land forces. Adopted and perfected after the war by many nations, close air support became a mainstay of U.S. fighters by the end of WWII and was used even more successfully in Korea and Vietnam.

In the early 1930s, the jet engine was invented. Credit is usually given to Sir Frank Whittle of Great Britain (first to apply for a patent) and Dr. Hans von Ohain of Germany, whose engine was installed on a Heinkel He-178 and was the first to fly in 1939. During the war, Germany, England, and America continued working on jet engines and the aircraft they would power. Hitler planned to develop a jet-powered bomber but finally had to settle for a fighter - the Messerschmitt Me-262, which was generally untouchable by allied propeller aircraft because of its speed. However, the Me-262 had a limited range because of excessive fuel consumption and limited targeting capability at high speed. Fortunately, the war ended before it could be perfected.

At the same time, the atomic bomb was under development, and it is now well documented that the Germans had almost succeeded in developing one when the war ended. On August 6, 1945, the Enola Gay dropped the first atomic bomb on Hiroshima, deliverable only by an aircraft like the B-29 that could carry heavy munitions. Bockscar, another B-29, struck Nagasaki three days later, arguably hastening the surrender of Japan.

The 1950s and 1960s and the Cold War
In the wake of World War II, the future of aviation in America looked extremely bright. No idea or concept seemed too farfetched to consider, and anything seemed possible. The Korean War signaled the end of the propeller-powered fighter and ushered in the era of the jet fighter. The jet fighter tactics used today were developed during dogfights between North American F-86s and MiG 15s over Korea.

The Century series of aircraft for the Air Force, consisting of supersonic fighters (the F-100, F-101, F-102, the F-104, Starfighter [Mach 2 plus], the F-105 and the F-106), new bombers (the B-47 and the B-52, which is still in the inventory), jet airliners, and the XB-70 (designed to sustain Mach 3 and, for its size, probably the most remarkable aircraft of all) were all in development. The X-15 had extended manned flight all the way to Mach 5. The F-12, which led to the Mach 3 SR-71 high-speed reconnaissance aircraft, was flying. Sixty-five years after Wilbur and Orville’s remarkable first powered flight, the golden age of military aviation had arrived.

America’s air fleet was developed with the Cold War in mind. The need for long-range bombers that could carry nuclear weapons led first to the B-47 and then to the B-52. Fighters were designed for both conventional and nuclear wars; aircraft as early as the F-84 and the F-100 were modified to carry nuclear weapons. Almost all subsequent fighter aircraft have retained that capability.

The war in Vietnam was a crucible for the development of new systems, the use of aircraft in unaccustomed roles, and the development of tactics for air attack (many of which have since been perfected in the conflicts in Kosovo, Afghanistan, and Iraq). In Vietnam, the B-52 was modified to carry enormous quantities of conventional bombs, which may well keep the B-52 in the inventory until approximately 2040 in this capacity; for more heavily defended targets, the B-52 can be a missile platform for launching high-speed, long-range cruise missiles. When existing aircraft were unable to destroy a bridge span easily, engineers and visionaries returned to the drawing board to develop precision-guided munitions. They also invented missile systems to strike radars that guided enemy ground-to-air missiles, improved the sensitivity, sorting, and tracking capabilities of aircraft radar, and created heads-up displays and many other innovative features.

Efforts to supplement conventional aircraft with vertical-takeoff systems were also under way. The British developed the Kestrel, which became the Harrier aircraft used by the U.S. Marine Corps. Vertical-takeoff aircraft are not restricted to airfields and can be dispersed to tactical advantage. The latest technology is in the propeller-powered V-22 and the vertical/short takeoff and landing (V/STOL) version of the F-35 Joint Strike Fighter now in development.

Today’s Fighters
With the lessons of Vietnam still fresh in the minds of developers and the need to cope with Soviet aircraft in a larger war still pressing, a new generation of military aircraft was beginning to emerge. It was clear to military planners that an air war with the Soviet Union would be difficult for American and allied air forces to win. Intelligence indicated that not only was a new generation of Soviet aircraft under development, but also that the numbers of Soviet aircraft were staggering. To prevail in the European battle scenario, the United States and its allies would have to destroy at least four Soviet aircraft for every one of ours. This "exchange ratio" of four to one meant that our aircraft and systems had to be superior, in fact, vastly superior. This necessity gave rise to the next major evolution of military jet aircraft- the F-15. Designed primarily for air-to-air combat, the F-15 was a remarkable engineering feat.

In the meantime, the Russians were far from idle. Based on experience with the Mig 15 and Mig 17, the Soviets developed aircraft comparable to the best aircraft in the U.S fleet. The Sukhoi Su-27 was designed specifically to offset the F-15; the MiG 29 is in the same category. Both aircraft have unusual handling characteristics at high angles of attack that our systems cannot emulate.

Shortly after the debut of the F-15, there was a campaign to produce a less costly, lightweight fighter. Two lightweight prototypes were procured, the General Dynamic (now Lockheed Martin) F-16 and the Northrop F-17; a fly-off competition was won by the F-16. The F-16 was the first "fly-by-wire" production aircraft. The fly-by-wire capacity eliminated the need for backup mechanical control systems, which had added considerable weight to the aircraft. The lighter weight also contributed to the F-16’s extraordinary maneuverability. These aircraft represent the culmination of the fighter jet; in fact, additional maneuvering capabilities would only exceed the pilot’s physical ability to withstand the forces generated. Thus, the F-16 is limited by its onboard computer to "g" loads pilots can accommodate (usually 9 g’s).

Later, a naval version of the F-17 (now in the hands of McDonnell Douglas) was purchased by the Navy and designated the F-18. McDonnell later merged with Boeing, which is now the prime contractor for the F-18 and its variants, as well as the F-15. These three aircraft, the F-15, the F-16, and the F-18, with their variants, still comprise the heart of the U.S. fighter fleet. They will not be surpassed until the F/A-22 enters the inventory (around 2005). The F-16 is now also flown by Belgium, the Netherlands, Norway, Denmark, and a host of other nations. Japan has built its own version of both the F-15 and the F-16; Israel also operates both. Australia and Canada have opted for the F-18.

At the same time, new aircraft were appearing. In the late 1970s, stealth aircraft were invented. Based on the musings of Russian scientists, "stealth" methods reduce radar cross section so that stealth aircraft are nearly invisible to enemy radars. The technology involves the application of materials that absorb radar energy and aircraft shape management (e.g., the F-117 and the B-2). Stealth techniques have increased the probability of survival of attacks into hostile airspace.

Around 1980, the concept of the advanced tactical fighter, now known as the F/A-22, emerged (Figure 7). Designed to meet the demands of the Cold War, this remarkable aircraft was developed to fly safely on the "red" side of the battle area; it not only has stealth capabilities, but also has the ability to supercruise (i.e., to fly at supersonic speeds without the use of an afterburner), thereby reducing fuel flow, extending range, and limiting the time of exposure to enemy antiaircraft systems.

To understand the "birthing" difficulties of the F/A-22, one has to understand some of the basics of modern aircraft procurement. All military aircraft must be justified within the authority of the President’s budget, and the services develop prospective budgets for each new system based on several planning factors: the total number of aircraft needed to meet force requirements; nonrecurring development costs; unit cost estimates based on assumptions about production rate; predictions by vendors of production learning curve effects; and other factors.

Initially, the F/A-22 was expected to be operational by the early 1990s; that date has been extended to at least 2005. The total number of aircraft and the anticipated production rate have both been reduced to well below the initial pricing parameters. When you add the costs associated with the F/A-22’s incredibly complex avionics systems, which has been reinvented over and over again, you begin to understand the extreme increase in cost of the aircraft. Nevertheless, the F/A-22 will almost certainly be the most capable fighter aircraft ever built.

Thoughts for the Future
Since WWII, no one has even tried to challenge American airpower or that of our European allies. The Russians are mired in the aftereffects of the Cold War and a collapsed economy. Once-prominent aircraft manufacturers have been reduced to selling their inventories of fighter aircraft to foreign buyers, but there are few takers, and new systems are beyond their financial reach. The Japanese have been content to operate modified American systems. The Chinese, whom some believe will be the greatest threat in the future, do not seem intent on demonstrating advanced aircraft systems. The Europeans are cooperatively building fighter aircraft systems with capabilities that will rival, but not exceed, the capabilities of the F-15 and F-16, not to mention the F/A-22. The newest fighter, the F-35 Joint Strike Fighter, is only marginally superior to the F-16, although it does have significant flexibilities, efficiencies, and some new capabilities, and it is being produced with advanced manufacturing techniques.

It is said that no American serviceman has been killed in battle by enemy air attack in the past 50 years. The Army now designs new systems based on the assumption that protection from above will almost always be provided by friendly air forces. Will our military aircraft fleet ever be challenged? If not, how do potential adversaries approach conflict with the United States? There are several possible scenarios.

The first scenario requires little analysis. In this scenario, there will be no technologically adept opponent of nearly equal capabilities for the foreseeable future. The grossly asymmetrical forces arrayed against us will not require improvement to our air forces. These dispersed, clandestine, and supranational enemies present few targets from the air, and the usefulness of airpower against these adversaries will continue to be marginal. Thus, our current force seems more than adequate.

In the second scenario, we assume that a technologically adept military competitor appears. In this case, we should be forewarned by intelligence agencies so that we can take the necessary steps to improve our systems. The current force, as modified, with the addition of the F/A-22 and the F-35 should be sufficient for at least the next 20 years. This scenario currently prevails among military planners.

A more worrisome scenario would be the nullification of U.S. military airpower by an unexpected technological advancement or breakthrough that cannot be countered quickly. Examples might include systems that negate stealth advantages coupled with weapons we cannot counteract or space-based systems that are out of our reach that could destroy our assets quickly. One can only hope that engineers somewhere are working on countering these eventualities.

With the advent of new unmanned aircraft systems, the risk to human beings may be greatly reduced. These systems are still in their infancy, probably comparable to aircraft in the 1950s, but the possibilities for their future application are endless, and new tactics are being developed every day. But I do not believe the age of the fighter pilot is over, although the future will be very different. Unmanned machines under the control of fighter pilots flying in proximity may well represent the air power of the future- unmanned machines that can accomplish feats beyond the physical abilities of any man or woman, without the human risk.

Finally, we must consider space as a future battlefield, as well as systems that will allow its exploitation and will have some synergistic effects on the capabilities of air-breathing systems. In the 1960s, partial-orbit or fully orbital military systems were under consideration but were not implemented. Although the use of space for military power could be dreamed of, the underlying enabling knowledge and technologies did not yet exist. Everyone acknowledged that the first country to "own" space would "own" the planet, but the military did not have the technologies, budget, or the inclination to lead the nation to space. Even the National Aeronautics and Space Administration (NASA), after visiting the moon, was content to fly the shuttle in low Earth orbit and develop unmanned systems to explore other planets. This attitude persists to the present day.

In the late 1970s, the concept of an "aerospace plane" for space access emerged, but after the expenditure of more than a billion dollars, the project was shelved as technologically unachievable. The dream of flying to orbit in a hybrid, air-breathing/rocket system had to be abandoned. Later attempts were equally unsuccessful.

In various laboratories, experimentation is under way to develop ramjet and scramjet engines as the only way to achieve and sustain air-breathing flight above Mach 3 in the atmosphere. But after 50 years of effort, no production systems have emerged. In fact, it has only recently been verified that scramjet engines can actually fly and produce positive thrust; and this was accomplished in Australia.

In short, despite our ingenuity and engineering skill, we have not realized the benefits of greatly increased speed for commercial and military aircraft systems. Once Boeing dropped out of the supersonic airliner business, the Concorde was the only supersonic (Mach 2) commercial production aircraft to be operated successfully (but not economically).

In 1963, President Kennedy challenged Americans to land a man on the moon by the end of that decade and return him safely to Earth. Although in hindsight, this challenge seems foolhardy, it was met in 1969. Many now argue that the effort wore us out without delivering anything useful. I strongly disagree. Although many aspects of the project were premature, no one can dispute that the Herculean effort exemplified the best that our engineering talent could deliver. Grand plans need grand strategies, strategies that include a road map for what comes after the immediate challenge has been met. And there was no post-Apollo plan supported by the American public. This was not the fault of the engineering community but a failure of national leadership.

Three decades after Apollo, we still have no comparable vision for man in space. A plethora of unmanned systems have contributed collectively to our current standard of living and our nation’s military capabilities. Communications satellites provide nearly instantaneous television pictures from halfway around the planet. Weather satellites warn of impending disasters. Reconnaissance satellites keep the military informed of the activities of potential adversaries. Low, medium, and geosynchronous stationary orbits are filled with vehicles and systems, and new microsatellite arrays will soon be launched. The success of the global positioning system (GPS) satellite array has been phenomenal. But, with the exception of the space shuttle and temporarily manned orbiting systems, our space capability does not involve the presence of human beings and does little to satisfy our thirst for exploration. One can hope that the recently enunciated space vision of President Bush will lead to the development of a strategy for the moon and beyond that can be fully supported by the American people.

The challenges in materials science, thermal management, and many other technical areas to operate within the atmosphere at speeds above Mach 5 are too great, I believe, for an economical manned system (missile systems may be possible). Hybrid horizontal takeoff and landing systems, using both rocket and air-breathing propulsion for access to space, seem more likely. These systems could be useful for both military and commercial purposes and could avoid some of the extreme challenges of very high speed operations within the atmosphere. Military aircraft of the future will almost certainly operate in both air and space.

In the twenty-first century, we will see the dawn of the space fleet. The U.S. Department of Defense (DOD) is currently championing the National Aerospace Initiative (NAI), a communications and coordination device to bring together NASA, DOD, and service executives to discuss the development of hypersonic and space-access systems and space technologies. NAI offers the prospect of eliminating redundancies, encouraging cooperative ventures, and taking advantage of opportunities for economies and efficiencies that might otherwise be missed. A multilevel organization for cooperation has been established to accomplish NAI goals. If NAI is endorsed by the President, it could ensure U.S. advancement to space. Great challenges lie ahead, but I believe we can overcome them- as we carry on in the spirit of innovation that characterized the evolution of military and commercial aircraft in the twentieth century.

About the Author: Michael A. Clarke is director of the Air Force Science and Technology Board of the National Research Council, a retired Air Force colonel, and a former fighter pilot, test pilot, and acquisition officer.