From Kettering Bug to Cruise Missile

The craft was made of papier-mache reinforced with wooden members and had cardboard surfaces on wings spreading less than six feet (1. 8 metres). It weighed 300 pounds (136 kilograms) and carried another 300 pounds of explosives.

General H. H. ‘Hap’ Arnold provided this description: ‘It took off from a small four-wheeled carriage which rolled down a portable track. Its little two-cycle 40-horsepower engine built by Henry Ford met requirements for both pressure and vacuum necessary to operate automatic controls. The actuating force for controls was secured from bellows removed from player pianos. They rotated cranks which in turn operated elevators or the rudder.

‘Direction of the flight was insured by a small gyro, elevation from a small super-sensitive aneroid barometer so sensitive that moving it from the top of a desk to the floor operated the controls. This kept the Bug at its proper altitude. The entire device cost about $400. ‘ The Bug was, according to contemporary reports, ‘half player piano and half cash register. ‘

Its first flight at Dayton’s South Field on October 2, 1918 was notable, if only for its eccentricity. Instead of maintaining horizontal flight, it began to climb. At about 800 feet (244 metres), it turned over and abruptly went into a dive directly toward the distinguished military visitors assembled for the flight. The craft buzzed them several times before crashing. Subsequent flights proved its worthiness but the war soon ended and the Bug was shelved.

Cruise missile technology submerged for almost a quarter century – until World War II when it resurfaced as the relatively crude but extremely frightening German V-1 ‘buzz-bomb’. Powered by pulse-jet engines, these Nazi weapons wreaked havoc both physically and psychologically on English and Belgian cities. They lacked the range, accuracy and explosive power required to be effective by modern standards, but they were mightily impressive to those in the target areas.

Cruise missile development resumed in the US after World War II. In 1946, the Navy began the design of a missile to meet a requirement for a ‘flying bomb’ capable of being launched from a submarine or ship. Driven by a turbojet engine, this 33-footlong (10-metre) subsonic, unmanned monoplane was built by Chance Vought and was first flown in 1951. It could carry a nuclear warhead almost 600 miles (965 kilometres) from a launching ship and fly at about 600 miles an hour, or just under Mach 1. Although it was powered in flight by a turbojet engine, it needed two solid-fueled boosters for launching.

In all, there were more than 1000 Regulus launches, including a landmark flight on June 8, 1959 in which a missile delivered 3000 letters from the US submarine Barbero to the Naval Air Station at Jacksonville, Florida, a distance of 100 miles (177 kilometres). A supersonic follow-on, Regulus II, also was developed. It was 57 feet (17. 4 metres) long and was capable of Mach 2 speeds. This missile was used as a target drone for the testing of Boeing-built Bomarc Interceptor missiles. Many unmanned aircraft, drone missiles and the like have been developed in the US and elsewhere since Regulus,. and many of them could qualify as cruise missiles. Following are some examples:

MATADOR. Built by Martin and first tested in 1949, this ground-launched medium-range guided missile was, in effect, a pilotless bomber. In fact, it was known as the B-61. It was powered by a turbojet engine and was launched from a truck with the help of solid-fueled boosters. It had a wingspan of almost 29 feet (8. 8 metres) and a body length of almost 40 feet (12. 2 metres).

MACE. Also a Martin missile, Mace was an outgrowth of Matador II. There were two versions: The ‘A’ model which used automatic terrain recognition and navigation guidance system, and the ‘B’ model, which had an inertial guidance system. Both were powered by turbojet engines and were capable of attaining supersonic speeds in their terminal dives. Mace, which had a 44-foot (13. 4 metres) length and 23-foot (7 metres) wingspan, began development in 1954 and was operational five years later. The ‘A’ version had a range of more than 650 miles (1046 kilometres) and the ‘B’ model was capable of more than twice that.

SNARK. This Northrop-built weapon was the first US missile of intercontinental range. It was a turbojet-powered high-wing monoplane with a length of almost 68 feet (20. 7 metres) and a wingspan of more than 42 feet (12. 8 metres). This subsonic surface-to-surface weapon became operational in 1959. It used a stellar-monitored inertial guidance system.

BOMARC. This Air Force supersonic ground-to-air weapon was designed by Boeing to destroy attacking aircraft and airborne missiles. Its range of 400 miles (643. 7 kilometres) allowed it to be based in remote areas on a constant combat-ready basis. Powered by two ramjets mounted on pylons under the body and launched by a solid-propellant booster, this missile- Operated at more than twice the speed of sound and had a kill capability ranging from sea level to altitudes above 80,000 feet (24,384 metres). It was guided by radio commands from land-based air defence systems. Bomarc made its first full-duration flight in 1961.

TALOS. This Bendix-built surface-to-air and surface-to-surface missile saw duty off North Vietnam during the Vietnam war. Guided by beam-riding with terminal semi-active radar homing, this missile is ship-launched and carries either high explosive or nuclear warheads at supersonic speed. It is of short range, about 65 miles (104. 6 kilometres), and is powered by a solid-propellant booster and a ramjet sustainer. It has a length of almost 32 feet (9. 8 metres) and a 91⁄2 foot (2. 9 metres) wingspan. Talos was first fired in 1959.

HOUND DOG. This strategic air-to-surface weapon was built by North American Aviation and entered service in 1961. Its slender, cylindrical body was almost 43 feet (13. 1 metres) long and its delta wings had a total wingspan of 12 feet (3. 7 metres). It depended upon an inertial guidance system for the supersonic delivery of its nuclear warhead.

QUAIL. McDonnell Aircraft built this turbojet-powered air-launched decoy missile. Though only about 13 feet (4 metres) long, this missile was designed to fly pre-planned patterns and carried electronics which enabled it to look like a B-52 on enemy radar screens. It entered development in 1955 and was deployed beginning six years later.

SCAD. Though never built, Scad was a forerunner to the air-launched cruise missile. It was to be a Subsonic Cruise Armed Decoy, a concept developed by Boeing. To be launched from the B-52, Scad was to saturate, confuse and electronically jam enemy area defences while the bomber delivered its payload of Short Range Attack Missiles (SRAM), also developed by Boeing. The missile was to carry a nuclear warhead, ensuring that an enemy could not afford to ignore it even if it was able to identify it as a decoy. The Air Force terminated the Scad programme in 1973 and redirected Boeing’s efforts toward the advanced development of the Boeing Air Launched Cruise Missile.

AGM-86A. This Boeing-built ALCM was a forerunner of the longer-range AGM-868. The ALCM-A had a body length of 14 feet (4. 3 metres) and a wingspan of a bit more than 10 feet (3 metres). Its range was in the order of 750 miles (1207 kilometres).

AGM-868. Today’s Air Launched Cruise Missile. Produced by Boeing Aerospace Company, this strategic weapon has a range of more than 1500 miles. It measures 20 feet 9 inches long and has a wingspan of 12 feet. The US Air Force has announced plans for acquiring more than 3000 of these nuclear missiles for deployment on B-52 bombers. They also will be carried by the B-1B bomber.

The Boeing AGM-868 provides the US Air Force with a strategic bomber weapon system that can penetrate enemy defenses and streak to targets deep within the enemy’s borders with great accuracy.

It is, in effect, a small, extremely versatile, unmanned, self-guided aeroplane which is capable of electronically reading the terrain over which it flies. It compares these readings with maps stored in its onboard computer, guiding itself through the enemy’s defense systems to predetermined targets.

Operational missiles will be armed with W-80 nuclear warheads.

The ALCM’s range of more than 1500 miles and small radar cross section give the Air Force a weapon that can be launched over non-hostile territory and still reach major targets. It will be carried by the B-52 bomber and is compatible with the B-1B long-range combat aircraft. The B-52 bomber is capable of carrying 20 ALCM’s-eight in a rotary launcher in the bomber’s weapons bay and another 12 on pylons under the wings. Initial deployment will be on pylons.

The original ALCM was about 14 feet long and was designed to fit onto the B-52 and B-1 weapons launchers with the Short Range Attack Missiles (SRAMs), also a Boeing product. It was designated the AGM-86A and had a range of about 700 miles. In all, seven AGM-86A’s were built during a developmental and testing program. Six were launched in 1976 from a B-52 bomber in test flights which demonstrated the missiles’ capabilities in an Operational scenario. The seventh missile was presented to the Smithsonian Air and Space Museum.

Boeing also designed a longer version of the AGM-86A called the Extended Range Vehicle. It was this missile that grew into the current AGM-86B after President Jimmy Carter cancelled the B-1 program in 1977.

At that time, the program was placed under the direction of the Department of Defense’s Joint Cruise Missiles Project Office and enlarged to include General Dynamics in competition for the air-launched strategic role.

Boeing and General Dynamics each conducted 10 flights of its missile system in the competition. Boeing’s segment of the flight test program began on August 1, 1979 and concluded on January 22, 1980. After evaluation of the competitive flight data and the technical, cost and production proposals of both companies, the Boeing AGM-86B was chosen as the winner of the competition.

The first operational ALCM’s were received by the Strategic Air Command’s 416th Bombardment Wing at Griffiss Air Force Base, N. Y. , on January 12, 1981. Griffiss is to be the first base at which ALCM’s will be operational, scheduled for December 1982.

This initial operating capability will comprise 16 B-52G bombers equipped with 12 missiles each. The AGM-86B owes its pinpoint accuracy to a guidance and navigation system which steers the missile to its target by comparing the terrain over which it flies to maps stored in its onboard computer system.

This terrain contour matching combined with an advanced inertial guidance system allows extremely low, highly manoeuvrable flight while guaranteeing astounding accuracy.

Visualize this mission:

A B-52 bomber and its cargo of ALCM’s are dispatched from a US Air Force Strategic Air Command base to somewhere high over the ocean approaching the enemy’s coastline. A cruise missile is launched. It dives almost to wave-tops, sweeps over the beach, then darts under and by the enemy’s radar defenses by skimming along valleys and around mountains. Finally, somewhere within its range of more than 1500 miles (2500 kilometres), the ALCM zeroes in on its target and strikes home.

How does all this happen? Let’s examine the mission, step-by-step.

When the ALCM first is deployed aboard the B-52 bomber, its guidance and navigation system is inert and without electrical power.

After takeoff, the B-52’s inertial navigator is aligned and its reference angles and velocity changes are fed into the ALCM’s inertial navigation equipment: a P-1000 inertial platform and an LC-4516C computer. Data from the B-52’s radar altimeter and barometric altitude system also are fed into the ALCM’s inertial equipment. Updates from these B-52 instruments are channelled to the missile every 60 seconds. Targeting information and mapping data over which the missile will fly are fed into the ALCM computer. The ALCM now is turned on, knows where it is, where it is heading, and is ready to go. Upon launch from its mother ship, the ALCM becomes an independent, self-directed unit. Its heart is its computer. Its lifeblood is the information fed it by:

• The inertial platform, which provides reference angles and changes in velocity.

• A radar altimeter is used when cruising at less than 5000 feet (1500 metres). This instrument provides both the missile’s

height above ground and the information needed to navigate in hilly terrain.

• The pitot static tube and temperature probe provide air data.

• Three flight control system rate gyros and a pitch accelerometer also are used.

The computer, using this data, guides the missile toward a predetermined point on the coastline. As the ALCM nears the enemy’s radar perimeter, it descends to wavetop level for its dash under the radar and over the beach. The radar altimeter now comes into prominence. It scans the landfall and develops a terrain height profile which is compared with data in the missile’s map storage device. Mapping information is furnished by the Defense Mapping Agency.

This map and others stored electronically aboard the ALCM are made up of matrices of many cells. Each cell in the matrix specifies a terrain height. The radar altimeter captures the profile of the overflown land and compares it with the cells in the map.

The difference between where the computer’s memory says the missile is and its actual position over the mapped area is fed through a Kalman filter, a digital smoothing and estimating technique that helps determine the navigational errors, pinpoints their sources and furnishes data necessary to make corrections. The navigation system then steers the missile toward the next predetermined map area.

At first landfall, the missile’s map may be of an area measuring in the tens of miles. As the missile proceeds toward its target, the maps would be of smaller and smaller areas, as the guidance system fine-tunes out practically all errors.

When it comes to melding the ability to know where you are and the ability to do something about it, the ALCM is right on target. The cruise missile has well and truly arrived.