1936: Focke's First Practical Helicopter

Professor Heinrich Focke turned to the backwater of helicopter development. His prototype helicopter, the Fa-61, was airborne in 1936, and can claim to be the first practical helicopter. It had twin counter-rotating rotors set on outriggers and started a German - and Soviet tradition of multiple counter-rotators. During 1937-8 it established helicopter records by reaching a speed of 76 mph, an altitude of 11,243 ft, _and remaining airborne for 1 hour 20 minutes. In 1940 Focke made the much larger Fa-223 with a 1,000 hp engine. This six-passenger craft was the world's first production helicopter. Equipped with a winch and a quick-release hook, it was given trials as a 'flying crane' and as an air-sea rescue vehicle. In mountain operations it reached 23,400 ft with a load of nearly 2,000 lb.

1939: Sikorsky Makes the Single Rotor Work

The Russian engineer Igor Sikorsky made his first helicopter experiments in 1908 when he was 19. During the 1917 Revolution, he fled to the United States. There he designed transport planes and founded the largely Russian-staffed Vought-Sikorsky company in Connecticut. In 1939 he designed the VS-300 helicopter which established the modern helicopter configuration with a single main rotor and a small tail-rotor. The tail-rotor solved the problem of torque. This new approach took American helicopters to the head of the field. In 1941 a VS-300 with a 90 hp engine gained the world endurance record with a flight lasting 1 hour 32 minutes.

1942: The vs-300 Founds a Dynasty

By 1942 the VS-300 had proved itself the first practical single-rotor helicopter. It was fully manoeuvrable in all directions. Tilting the whole rotor changes the direction of flight because the rotor blades then bite into the airflow at a different angle and pull the craft to that angle. The type of helicopter with a single principal rotor became pre-eminent. New helicopters grew bigger and more powerful: smaller versions also were developed down to one-man midgets, such as the American Rotorway Scorpion which has a rotor diameter of 25 ft and weighs 805 lb.

1950S: Jet Turbines for Helicopters

The helicopter benefited from Jet Engine developments in the late 1950s; the turbine shaft of the jet engine proved ideal for turning the helicopter's rotor. For the first time the helicopter had enough power. This fostered the second burst of helicopter development which has pro such craft as the Russian Mil A-10 which in 1978 set up the helicopter speed record of 228-9 mph.

GRAVITATION

Gravitation is a very important force in the universe. Every object has a gravitational pull which is like magnetism. But, unlike magnetism, gravitation is not only in iron and steel. It is in every object large or small; but large objects, such as earth, have a stronger pull than small ones.

Isaac Newton, the great scientist of the seventeenth century, first studied gravitation. According to the law which he later produced everything in the universe attracts everything else towards itself. The sun attracts the earth and the earth attracts the sun. The earth attracts the moon and the moon attracts the sun. Although the bigger object has the stronger attraction, all objects, in fact, have some attraction too but we do not notice the gravitational pull of a book because the pull of the earth is very much greater.

The force of gravitation

Why does the earth always move round the sun, and not fly off into cold space? The sun's gravitation gives the answer. The earth always tries to move away in a straight line, but the sun always pulls it back. So it continues on its journey round and round the sun.

The sun is one of the stars in the galaxy, in which there are about 100,000 million stars. It is not in the middle of the galaxy, but rather near one edge.

There are millions of galaxies in the universe and so there are thousands of millions of millions of suns. Many astronomers believe that some of these suns have planets as our sun does.

Gravitation is the force which holds all the atoms of a star together. It holds the sun together and it holds the atoms of the earth together. It holds us on the earth.

A MACHINE SHOULD WORK, A MAN THINK

The robots of our time resemble humans very little. According to specialists, the main thing for them is not to look like people, but to do their work for them. Factories which are equipped with automatic machine tools, transfer lines and management information systems place a lot of hope in them.

Automation sought out areas where a robot can operate as well as a person but where people don't like to work. In other words, man has created the robot so as not to become a robot himself.

The first generation of robots appeared in the 60s and they were complex and capricious in maintenance. They could perform operations of the type "take off—put on" or "pick up — bring". They could pick up items only from definite positions determined by a rigid programme.