Document created: 22 October 03
Air University Review, September-October 1973
Lieutenant Colonel E. J. Kellerstrass
A new threshold in the history of air power is opening on a scene altered by the impact of a new weapon-delivery mode. Although it did not come in with the explosive impact of the thermonuclear weapon or the ballistic missile, it will rewrite the books on aerospace doctrine. The Remotely Piloted Vehicle or RPV is here as a viable element in the arsenal of aerospace power. Its use for each of the broad Air Force mission areas—reconnaissance, air-to-ground strike, electronic warfare—has been demonstrated either in Southeast Asia in combat or over U.S. test ranges. The astute student of air power, the USAF planner, and the research and development community should be aware of the current and potential applications of the RPV in fulfilling aerospace missions. The purpose of this article is to familiarize the reader with the RPV and aspects of a complete RPV weapon system.
influencing factors
Since mid-1970 the aerospace trade journals have been lauding the RPV. Why this apparent sudden interest in the use of RPV’s? The answer lies in two important factors that have emerged in modern aerial warfare: costs of new aircraft and increased effectiveness of defensive systems. Since World War II the cost of tactical aircraft has increased from tens of thousands to millions of dollars each, with some next-generation vehicles costing more than $15 million each. This is an increase in excess of two orders of magnitude. Thus costs have driven modern aircraft to the point of being limited, high-value assets. Improved defense systems have necessitated the use of more sophisticated and costlier tactical aircraft, but with higher attrition rates. The improved defense has also necessitated a three to fourfold increase in support aircraft for electronic countermeasures, Combat Air Patrol, etc., which adds to the cost.
As far as numbers are concerned, the balance of military power in Europe is weighted in favor of the Warsaw Pact nations. They have more battle tanks and greater troop strength than the North Atlantic Treaty Organization (NATO) forces and twice the number of tactical aircraft. Added to this potential capability are advanced mobile radars and thousands of antiaircraft guns and surface-to-air missiles.
Clearly, aerospace power will be a decisive factor in the event of hostilities. But because of vehicle and defensive system costs, our conventional resources will be limited. The RPV offers promise of countering this seemingly overwhelming strength of the Warsaw Pact nations, however. This is not to say that current weapon systems are to be replaced by the RPV, but the RPV will augment manned vehicles so as to enhance their survivability and ability to perform their missions.
Why the remotely piloted concept? The unmanned craft complements manned aircraft by providing relatively low-cost systems to be deployed in large numbers in order to overwhelm the defensive systems. The RPV is built with attrition in mind and would be employed in large numbers against highly defended targets. It is fearless, avoids the extreme exposure of expensive manned systems, and reduces the number of potential hostages. During World War II, Allied air operations in Europe resulted in the loss of about 40,000 aircraft and 160,000 crewmen.1 Another possible consideration for using RPV’S is during periods of increased tension; reconnaissance by unmanned vehicles may be acceptable without precipitating open hostilities.
history
In its most simplified form, the RPV lineage dates back to four centuries before Christ, when the Chinese first introduced the kite. Later, a camera was placed on a tethered balloon during the Civil War and still later on the leg of a homing pigeon during World War I. However, it was 1915 before invention of the first modern military version of an RPV, the Kettering Bug.2 It was envisioned as a remotely controlled weapon that would shed its wings and dive as a bomb upon completion of a crudely preprogrammed course and distance. It did not become operational since the requirement ended with the cessation of hostilities. The concept was not developed further because it suffered the fate of many research and development attempts today: cancellation for lack of funds.
As early as 1924, such men as Hugo Gernsback recognized the potential application of a “pilotless plane which sees” remotely via a television link and radio control. In 1931, accompanying a reprint of Gernsback’s paper in Television News, it was stated that although the idea may have appeared fantastic in 1924, “most of those who read this article will live to see a television-controlled airplane a reality during the coming years.”3 (Primarily because of cost, the “coming years” took until 1972 before an RPV became a practical reality with the demonstration of the strike RPV.) However, development of a military RPV lay dormant, buried under the wraps of security classification, until 1938. Then the Army Air Corps let a contract to the Radioplane Company, subsequently to become the Ventura Division of Northrop Corporation, for three radio-controlled target drones. This development led to the first drone production line. The Air Corps designated this drone the A-2, which was followed by an improved version, the OQ-2A.
During World War II, the Kettering Bug again surfaced as a possible candidate for long-range bombing of the Axis powers.4 Because of a short 200-mile range, it was abandoned in favor of modifying battle-weary B-17s and B-24s, which were no longer suitable for manned operations, into drone configurations to attack heavily defended targets in the heartland of Germany and submarine pens along the coast of France. This plan also was abandoned because of prohibitive costs: the aircraft first had to be made airworthy. The German V-1 buzz bomb used during this period may also be classed as a drone.
In the years immediately following World War II, much of the R&D activity was focused on the guided missile program. The RPV found its role limited to target applications, which became the technological base for our current unmanned vehicles. A number of manned aircraft were modified for drone applications, again, primarily, in the target application. Some of these were the QB-17, QB-47, QF-80, QF-104, and QT-33.
The use of functional drones in the USAF began in 1948. The Ryan Aeronautical Company was awarded the first contract for a subsonic, jet-propelled, unmanned aircraft. It was designated the XQ-2. The primary purpose of this drone was for test and evaluation of ground-to-air and air-to-air missiles. The production model was designated the Q-2A. The utility of the target drone for training of aircrews soon became apparent, but realistic target threat simulation was necessary. The Q-2A was not designed for the added radar augmentation and scoring devices. Wingtip pods were used, with resulting degradation of aerodynamic performance. The drone was modified for higher performance. After building only three XQ-2B drones, Teledyne-Ryan proposed a new design with adequate internal space for augmentation and scoring devices and with a larger engine. This drone (later designated the BQM-34A Firebee by Navy and Air Force, MQM-34D by the Army) is a high subsonic vehicle, near Mach 0.9, capable of operating at altitudes from 200 to 50,000 feet using remote radio control. It went into production in 1959.
current RPVs
The current inventory of USAF drone/RPV systems is directly related to the manner in which the programs developed historically. Usually, an existing target drone or a derivative thereof was selected for modification to meet an urgent operational reconnaissance need rather than expend the critical time required to design and develop the optimum remotely piloted vehicle. As these systems operated successfully and obtained the desired results, more operational needs were identified for them.
Tensions during the early sixties provided the catalyst to employ the RPV in other than target applications. In 1962, two research and development photo reconnaissance RPV’s were created out of modified Firebee target drones. From this humble beginning an operational reconnaissance capability evolved, which was used in Southeast Asia. This fearless workhorse for low-level reconnaissance is the AQM-34L.
Since then, RPV’s have been developed for other applications, but operationally they have been used primarily in the reconnaissance role or as target drones. Another mission application was for tactical electronic warfare support. The activation of the 11th Tactical Drone Squadron on 1 July 1971 (assigned to the 355th Tactical Fighter Wing at Davis-Monthan Air Force Base, Arizona) marks the beginning of employing unmanned vehicles in tactical operations.
drone/RPV system
The design of a drone/RPV must be considered from the point of view of a total weapon system. The main elements of such a system are the airframe, launch subsystem, payloads, propulsion, command/control, and recovery subsystem. The airframe becomes the integrating element for the total system. The design of such a system must be specifically tailored to the missions it is to accomplish. The navigation techniques employed, internal guidance, flight control, fuel distribution to include its transfer for weight-balance control, etc., must all be designed for automatic and/or remote control.
The mode of launch is critical in the design and must include provision for total system checkout and fueling. Structural stability and flight control are vital considerations. The USAF suffered some painful experiences as it went through the learning curve in developing techniques for zero length ground launch and DC-130 airborne launch. The missions are generally the driving factor in the design of an unmanned vehicle, for payloads such as photo reconnaissance (high, medium, or low altitude), electronic countermeasures (active and/or passive, to include dispensers), and weapon delivery, to name a few. We must keep in mind that the unmanned vehicle is envisioned to be inexpensive, since it will be employed in high-risk areas with many losses due to enemy action.
The propulsion plant must be tailored to the mission; e.g., an engine for a high-altitude, long-endurance flight profile would be different from one selected for a low-altitude, on-the-deck, high-subsonic flight profile. Another prime consideration is availability in the research and development inventory. The development of a new engine for a high-performance RPV can be expected to take four or five years and some fifty million dollars.
Control-guidance is an essential element of an RPV system. Consideration must be given not only to control of the unmanned vehicle but also to control of its payload. Some means of recovery must be designed into most systems, although not for expendable or one-way vehicles. Current recovery techniques include the use of parachutes. Most operational Air Force systems use a helicopter recovery in what is designated as the Mid-Air Retrieval System (MARS). Here again, there was a painful learning curve. Early in its use, the losses (total destruction) due to MARS failure were about 50 percent. Recent years have shown over 90 percent success. Some current RPV’S being developed will weigh in excess of 13,000 pounds. These RPV’S will have landing gears and will be operated from runways.
RPV families
Unmanned vehicles may be classed into four broad categories, based on basic vehicle performance and design: target drones; high-altitude, long-endurance RPV’s; tactical RPV’s; and expendable drones.
target drones
Jane’s All the World’s Aircraft lists 34 drones, of which 65 percent are U.S.-built. Most of these are target drones that have been in the inventory of the military services for years in one form or another. Beechcraft Teledyne-Ryan, and Northrop are the leaders in the design and fabrication of drones in the United States. Beech alone has assembled more than 4500 drones since 1955. Currently the workhorse for the Air Force and Navy is the Teledyne Firebee. The Northrop Chukar (MQM-74A) is widely used by U.S. and NATO forces as a low-level target system.
Most of the target drones have been in the subsonic region of flight, whereas modern manned weapon systems require supersonic targets for test/evaluation and training. There are some small supersonic targets in the U.S. inventory, and larger, higher-performance vehicles are being developed. The latest USAF target drone is the supersonic BQM-34F. Most Air Force target drones have augmentation devices on board to enhance the radar or infrared (IR) signature so as to simulate a full-size target. As these are unsatisfactory for some aspect angles, new efforts are being directed toward full-scale maneuvering targets. In order to present more realistic targets, maneuverability and variable speed are being designed into even the small subsonic targets.
high-altitude, long-endurance RPV
The USAF has several efforts under way to develop a family of high-altitude, long-endurance (HALE) systems to fulfill a broad spectrum of important missions. “High-altitude” means that the RPV is at an altitude in excess of 40,000 feet during its mission aspect of the flight profile.
The Compass Cope program is a two-contractor flight-vehicle demonstration effort. The objective is to build an RPV with a sizable payload that will operate at high altitudes with long endurance. One approach, which is in the initial design stage, is based on technology developed for the Teledyne-Ryan AQM-91A. The other Compass Cope effort is based on a Boeing concept.
There are numerous missions and associated sensor platforms to which the high-altitude, long-endurance RPV may be applicable: time of arrival, distance measuring equipment, side-looking radar, reconnaissance, battlefield surveillance, air sampling, communication relay, etc.
tactical RPVs
There are four broad mission areas for this family: reconnaissance, air-to-ground, electronic warfare, and air-to-air. As an outgrowth of the intelligence activity, RPV’s are in the inventory for tactical photo reconnaissance. When the tactical requirements for real-time data are addressed in the near future, the payload configuration and operation must be more adaptable, to incorporate man’s decision-making abilities. Some of these systems will use RPV’s for real-time surveillance around fixed bases and near the forward edge of the battle area (FEBA).
One of the most exciting applications for the RPV is its use in the air-to-ground strike mission. Accuracy is more critical than yield. When attacking revetted hardened targets such as hangarettes, accurate delivery of the weapon is absolutely essential. It is extremely difficult for manned aircraft to deliver weapons with the necessary accuracy when the target is heavily defended with antiaircraft artillery (AAA) and surface-to-air missiles (SAM’S). Of course an RPV is fearless. Reconnaissance film from RPV’s in Southeast Asia clearly shows AAA in action and multiple SAM launches as the RPV passed over the target complex. Such situations can be expected to result in high attrition rates for the attacking vehicles. The relatively low cost of the RPV makes it an ideal delivery system for this type of mission. Although the primary interest at this time is the use of RPV’S against heavily defended, high-value targets, such as a SAM site, there is little doubt that close air support and classical interdiction missions could be considered in the future.
Currently, the tactical electronic warfare RPV developments have been limited to the Tactical Air Command’s Combat Angel Force. The airborne director in the DC-130A will have a launch control system for rapid checkout and launch of four drones, and flight control of multiple AQM-34H’s.
Probably the most complex RPV system will be employed in the air-to-air combat role. The concept of using an RPV in this mode was validated by the U.S. Navy. A mock dogfight was conducted with an F-4 trying to make a kill on a modified Teledyne-Ryan Firebee over the Pacific Missile Range. Additional engagements were conducted at Edwards AFB, California. The advantage of the RPV in accomplishing maneuvers of 12-g stress and in turning inside the manned aircraft gave the RPV an edge in the “battles.” Other air-to-air missions, such as tactical air defense, attack of special-purpose systems, and defense of our own special-purpose systems, are areas in which RPV’S could be utilized in the future.
expendable drone
A new family currently in the conceptual phase of system research and development is the expendable drone. The early history of drones was traced by the Kettering Bug. Not since then has an unmanned vehicle been designed in the U.S. with a one-way mission built into the concept. It is true that some droned manned aircraft and target drones have been employed on such missions, but they were not solely designed for just this type of mission. The expendable drone family is being developed to augment the tactical electronic countermeasure force. The concept is simple: to saturate the enemy defensive systems through the employment of large numbers of very low-cost drones. The objective is to capitalize on one of America’s greatest assets, her ingenuity and capability for high-volume productivity.
control guidance
Among the most critical problems associated with using large numbers of RPV’s in tactical operations will be control and data retrieval. This involves the simultaneous control of multiple vehicles operating in the same geographical area, interface of the RPV control-guidance system with the tactical air control system, and operation of RPV’S with manned aircraft in the same general airspace. Wide-band telemetry associated with such sensors as electro-optical and radar will require special considerations in view of possible enemy action to negate the RPV capability via jamming techniques.
control-guidance elements
The center of the control-guidance system is, of course, the RPV itself. This is the point about which the other elements are directed. The other obvious requirement is the remote station from which the RPV is controlled. It can be either a ground flight control central and/or an airborne director/relay. The latter is often the launch vehicle, as in the case of a DC-130. These control stations obtain status information on vehicle performance and provide control data to the RPV. There is on board the RPV a programmer for automatic control during some portion of the mission; further, it is used in the event of loss of communication between the vehicle and the remote pilot. There may be available some other means of tracking the RPV, such as a ground-control intercept radar, which could be a backup mode to the control system.
future trends
Some trends for the future in RPV’S are discernible. The RPV concept is not to replace manned aircraft but to complement the manned force, to improve tactical strike operations. For the near term, the technology is available, with no apparent breakthroughs required before the use of RPV’S can be exploited. Creativity and ingenuity in applying the technology to design concepts will be required in order that greater strides in this area can be accomplished and costs held to a reasonable factor. Some of the early challenges are in the areas of configuration design, propulsion, avionics, controls, and displays. Perhaps what is most important is that operational concepts and tactics for use of RPV’S definitely require exploring. How RPV’s are used and the methods employed will be as important to achieving operational success as the capability that is built into the vehicle. It is realized that this cannot be fully accomplished with studies or mathematical computer simulations. We will need early development of demonstration hardware and system prototyping that can be given to the user to develop tactics. This course of action can greatly accelerate the development of RPV systems as a viable force in the arsenal of aerospace weapons.
Man, pound for pound, is still the most effective component in our weapon systems. Sociological, political, and cost factors, however, may preclude the use of man and his high-value aircraft against highly defended targets. This situation could create a rather grim prospect for our foreign policy planners. Fortunately, the RPV may offer a way out of this dismal situation.
Hq Aeronautical Systems Division,
AFSC
Notes
The terms drone and RPV are used interchangeably throughout the article. Because of the various modes by which unmanned systems can be controlled and the fact that the remote pilot may or may not be opted in the control loop, the Drone/RPV Systems Program Office does not draw the fine-line difference that glossaries do.
1. William S. Graham, Astronautics & Aeronautics, May 1972, p. 38.
2. Charles Wiggin and Howard Eisenberg, “Our 1918 Missile,” Saga, August 1971, p. 18.
3. Hugo Gernsback, “The Experimenter,” November 1924, reprinted in Television News, March-April 1931, p. 10.
4. Wiggin and Eisenberg, op. cit.
Lieutenant Colonel Ernst J. Kellerstrass (M.S., St. Louis University; M.S.B.A., George Washington University) is Chief, Plans and Documentation Branch, Program Control Division, Drone/Remotely Piloted Vehicle SPO, Aeronautical Systems Division, AFSC. After ten years in meteorology, he served two years as geophysicist, Electronic Systems Division, and four years at VELA Seismological Center. He is a graduate of Air Command and Staff College.
Disclaimer
The conclusions and opinions expressed in this document are those of the author cultivated in the freedom of expression, academic environment of Air University. They do not reflect the official position of the U.S. Government, Department of Defense, the United States Air Force or the Air University.
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