A parachute is an umbrella like device used for slowing down the descent of a body falling through the atmosphere. Originally it was conceived as a safety measure against a probable plane crash or some malfunctioning in a flying aircraft. The parachutes have now found wide applications in times of war and peace; for safe dropping of supplies of essential items in times of emergency as well as for landing of personnel. The first man to demonstrate it was Louis-Sebastian Lenormand of France in 1783. Andre-Jacques Garnaria was first to use a parachute on regular basis demonstrating a number of exhibition jumps including one from a height of about 2400 m in England in 1801.
Early parachutes were made of canvas and later silk also came to be used. Captain Albert Berry of the U.S. Army made the first successful descent from an aeroplane in 1912. In World War II, parachutes were used for a variety of purposes; landing of special troops for combat, infiltrating agents into every territories and dropping of weapons etc. The modern man-carrying parachutes are made of nylon and are about 7 to 9 m wide when open. The cargo parachutes may be as wide as 30m when open.
Now the question arises how does a parachute work?
A parachute operates on a simple principle involving the force of gravity and air resistance — the two forces that act upon any falling object. The parachutes start falling towards the ground due to the pull of the force of gravity but the speed of the fall is checked substantially due to the resistance of air. At low speeds the pull of gravity is stronger than the resistance of air and at higher speed, the air resistance becomes more. Also, large flat surfaces offer more resistance than sharp surfaces. At a certain point the object reaches a speed called terminal velocity when air resistance and the pull of gravity are evenly balanced and, thereafter, the object starts falling at a constant speed. Therefore, an object shaped like a saucer reaches its constant velocity sooner. So it falls more slowly than one shaped like a needle.
As soon as the parachute canopy opens fully, the resistance of air slows down the descent of the parachutist so suddenly that he is jerked sharply. Now even parachutes with holes or slots in their canopies have been developed to reduce the force of these opening shocks.
The parachutes descend at a rate of about 5 m (15 ft) per second or slightly faster. But if dropped from less than 150 m above the ground, it can prove dangerous because this height does not allow the parachutes to open. The parachutists can control the direction of their descent by pulling on the shrouds and other operational devices.
Nowadays new parachutes have been developed which enable one to escape from supersonic planes. Parachute-jumping has become a popular sport in the United States and Europe. Today there are many clubs who organize national and international jumping events in which parachutists try to land on small targets on the ground.