Parachute

   The parachute was invented to allow men to escape from aircraft above the earth. Today it is also used for dropping cargo to places difficult to reach in other ways — cargoes of food and medicine and perhaps kits of firefighting tools. Fast planes may use parachutes to help in stopping or braking while landing.

   An open parachute looks like a huge stickless umbrella. Closed or folded into a bundle, it looks like the pack of an overnight camper.

   Any falling object has two main forces acting on it: the pull of gravity and the resistance of the air. gravity, the stronger of these forces, accelerates a man in free fall to about 120 miles per hour when falling at lower altitudes. The broad-surfaced open parachute increases the air resistance, assuring a slower, safer rate of descent.

   Once away from the aircraft, the falling parachutist pulls the ripcord, releasing a small pilot chute of about three-foot diameter. This catches the airstream and pulls out the larger, main chute or canopy which may be 24 feet in diameter. Spaced evenly around the canopy's edges are about 36 long ropes or shrouds, connected to the harness worn by the parachutist. A hole or vent in the top of the canopy stabilizes the canopy's descent by letting some air escape. Fast modern craft, such as jet fighter planes, have ejection seats so that the pilot can, by exploding a gun-powder device, be thrown clear of his aircraft and then open his chute to come down safely.

   The parachutes of today are made of nylon which has great strength and flexibility.

   The parachute idea has long intrigued men. Leonardo da Vinci in 1514 and Fausto Veranzio in 1595 worked out such devices on paper. But the first successful chute jump was made in 1797 by the French balloonist, Andre Garnerin. More than ten years earlier, the physicist Lenormand had practiced jumps from a high building.