parachute

parachute umbrellalike device designed to retard the descent of a falling body by creating drag as it passes through the air. The development of modern aircraft has led to many experiments in the aerodynamic problems of parachute design, with the result that the parachute of today is a highly efficient instrument. It must permit slow descent, must be highly stable, have little weight and a small area, and must retain its shape and maintain its balance in descent. Originally made of silk, parachutes are usually constructed from nylon or Kevlar. The traditional parachute takes the form of an umbrella, from which a series of cords converge downward to a harness strapped to the user; modern parachutes are wing-shaped, allowing precise control by the parachutist. By pulling on the appropriate control cords, the parachutist can spill air out of one side or another, and increase or decrease the lift of the wing, thus turning, diving, or even hovering under favorable conditions. Parachuting has its dangers. Folding a parachute requires a high degree of skill, and an improperly folded chute will not open. Before the parachute can be opened, the user must be clear of the aircraft in order to avoid entanglement, or fouling. Finally, the harness must be easily detachable, or else the parachutist might be drowned or dragged along the ground. The rate of descent for a traditional parachute is about 18 ft (5.5 m) per sec; sport parachutists manage to reduce that speed significantly. A French aeronaut, Jean Pierre Blanchard, claimed the invention of the parachute in 1785, and the first successful parachute descent from a great height was made in 1797 by the French aeronaut Jacques Garnerin, who dropped 3,000 ft (920 m) from a balloon. Parachutes began as an escape system for persons aboard balloons or aircraft unable to land safely. Modern military jet aircraft are provided with ejection seats that shoot occupants free of their craft and automatically release a parachute when they are at a safe altitude. In addition, since World War II parachutes have been used by the military for airborne operations and emergency resupply. In recent years, parachute jumping for sport, known as skydiving, has become popular. Parachutes are also used as braking devices for rockets, space vehicles, airplanes, and high-speed surface vehicles.

Bibliography: See study by B. Sellick (1981).



Author not available, PARACHUTE., The Columbia Encyclopedia, Sixth Edition 2008