Servo - January 2008

FIGURE 3. V-1 Drawing.

ings and closings, along with the series of explosions, caused the feared ‘buzz.’

I’ve heard model airplane pulse jets operate and can see why they have been banned in most populated areas; they sound a lot like a blaring horn. Much like the landing of a mosquito in a tent at night; the worry came when the V-1’s buzz stopped. It proved to be the world’s first operational cruise missile with it very unique guidance system (Figure 3).

The V-1 was launched from a steam catapult (much the same as today’s Navy planes launch from an aircraft carrier) and could reach speeds of over 580 km per hour. The V-1 was equipped with an automatic pilot that utilized a magnetic compass. Three compressed air-driven gyrocompasses were also used in the system. A master gyro controlled the pitch and roll through rudder and elevator surfaces by an air-driven servo system with corrections fed into the system by the magnetic compass. A weighted pendulum interconnected with the magnetic compass acted as a fore and aft attitude sensor, as well as an accelerometer. This ingenuous arrangement allowed simple turns to be accomplished by using only rudder control and no ailerons were required for banking.

The other two gyros damped out

errors and oscillations in the flight. Prior to launch, the V-1 crew would pre-set controls for the required height and direction of flight, as well as distance to their target. A vane anemometer (in reality, a small propeller in the nose of the V-

1) turned so many revolutions according to speed and distance traveled and acted like an odometer to tell the system how far the missile had traveled towards its target.

These turns unwound a preset mechanical counter that would throw the V-1 into a steep dive at the target area by causing the elevator to depress.

Would you believe that they actually used a tiny guillotine triggered by the counter to sever the air hose feeding the elevator, causing it to depress? I would have thought that a small valve would have done a better job. This abrupt dive angle caused the fuel to stop flowing to the engine in the early models, thus stopping the buzz, and the British knew a V- 1 was soon to strike. Later models powered themselves all the way to the target. Almost 12,000 V-1s were launched against Britain, though only about 25% actually hit significant targets.

The Unmanned Aerial Vehicles of Today

FIGURE 4. Micro UAV.

There is as much difference in the UAVs of today compared to Low’s and the Nazi’s creations as to the Wright Brother’s plane and the Boeing 787. Endurance, range, speed, sophistication of sensors, autonomy and, of course, cost have all spiraled upward.

There are two basic classes of unmanned aerial vehicles. The first is the classic combat weapon — the cruise missile. One example is the Tomahawk, the workhorse of the Navy. This sophisticated cruise missile proved itself in the Gulf War of 1991 when it was programmed to find its way from the submerged submarine that launched it, all the way to downtown Baghdad. News reporters were amazed to see it fly down a street and make a right turn to head to its final target. These weapons are like flying torpedoes; their purpose is to explode and destroy an intended target and never return home.

Some people may even include the unpowered smart bombs in this category. They are dropped from a plane, miles from a target, and guide themselves through varying control surfaces to a target that is illuminated by a laser beam. This beam can be from an overhead plane or from a soldier on the ground.

Another part of the combat category is the target and decoy missile that provides ground and aerial gunnery a target that simulates a real enemy aircraft or missile.

The second type of UAV includes the aerial scout such as the Predator, an AUV that returns to its home base. These vehicles can be autonomous or remotely controlled. The control can be from something as simple as a suitcase-sized console used by a single ground soldier or as complex as a trailer with several controllers.

These AUVs are not weapons in themselves, but can be loaded with small missiles or bombs and be fired or dropped by remote command. Most of this category, however, is relegated to passive spying or surveillance tasks. These can be reconnaissance AUVs that provide battlefield intelligence. There are also UAVs specifically designed for cargo and logistics operation. Government agencies use UAVs for research and development to further develop UAV technology.

There are so many variants of UAVs today that they can range from tiny vehicles under one ounce in weight to vehicles weighing many tons. Figure 4 shows a tiny AUV not much larger than a dragonfly, and there are operational vehicles even smaller. Figure 5 shows a member of the military hand-launching a vehicle that contains a video feedback system that it about the size of a typical R/C model airplane. It is known as the Small Unmanned Aerial Vehicles Advanced Concept Technology Demonstration (SUAV ACTD). These small AUVs bring battlefield awareness to small unit commanders. AUVs such as this can cover many miles in distance, and more importantly, send back images of many square miles of terrain without risking military personnel to hostile action.