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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 Originally made of silk, parachutes are usually constructed from nylon or Kevlar.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. Skydivingskydiving,
sport of descending partly by parachute from an airplane or similar craft. Engaged in for both recreational and competitive purposes, skydiving involves three phases of activity: the free fall, the descent with open parachute, and the landing.
..... Click the link for more information. and the more dangerous swooping (canopy piloting) and BASE jumping are forms of sport parachuting. Parachutes are also used as braking devices for rockets, space vehicles, airplanes, and high-speed surface vehicles.
See study by B. Sellick (1981).
in mining, a safety device for personnel cages. Parachutes are used in the event of a break in the hoist cable to catch a falling cage and to bring the cage to a smooth halt. The main element of the parachute is a set of safety catches. The standard parachutes accepted in the USSR for use with cages have a gripping device that provides support and shock absorbers to effect a smooth braking action; that is, the functions of catching and of smooth deceleration are separated. The 2TK (PTK), PTKP, PShTP, PKL, PKLSh, PKLZ, RKE, and PDP parachutes for vertical cage hoists are of this type.
If a cage equipped with a 2TK parachute (see Figure 1) starts to fall, safety catches with wedge-type couplings act on two brake cables, which are connected with shock-absorber cables that pass through the shock absorbers (the system of P. F. Pavlov and L. V. Pavlova). Smooth braking is provided by the flex of the brake cables and by the travel of the shock-absorbing cables. PKL parachutes with a wedge-type clamp, which act on only one brake cable, are used for hoists with guide rails on only one side. In the RKE and PDP parachutes metal or wooden guide rails are used as supports, and shock absorbers and shock-absorbing cables connected with the catch mechanism are installed on the cage itself. It is not necessary to use parachutes on hoists with four or more hoist cables.
In the case of personnel cars for inclined slopes, a runaway car is slowed by the stops, stuck in the trackway, of the brake carriage assembly suspended from a frame. Wooden beams below the frame are brought into action to assure smooth stops. The beams act as shock absorbers by making contact with the cutting teeth of the brake carriage. For slopes in excess of 30°, the mine cars are equipped with stops that have rail grips and guide paths that move along the rails.
Abroad, parachutes are used only in vertical shafts, and most parachutes are based on the principle of frictional resistance between the working members and the guide rails. For hoists with wooden rails, parachutes operate on the principle of frictional retardation.
REFERENCEBelyi, V. D., G. D. Lysak, and A. I. Petrakov. Shakhtnye parashiuty. Moscow, 1960.
S. IA. KHEIFITS
a device to decelerate an object moving in a resistant medium. A set of parachutes that open sequentially makes up a parachute cluster.
There are various types of parachutes or parachute clusters. Emergency parachutes are used for descent from malfunctioning aircraft flying at altitudes of up to 25 km with velocities to 1,400 km/hr. Landing parachutes are used to safely land freight, people, and unmanned and piloted spacecraft (the Soviet spacecraft Cosmos, Soyuz, and Luna 16 and the American Gemini and Apollo spacecraft). Brake parachutes serve to shorten the landing
run of an airplane, for example, on a wet or icy runway, or to slow the descent of the star of an illumination rocket in order to prolong illumination of the terrain. They are also used to retard to a predetermined rate the descent of scientific equipment into a planet’s atmosphere, for example, during the smooth descent of the unmanned probe Venera 8 into the atmosphere of Venus. In addition, they are used for braking racing cars during tests and emergencies and for slowing boats before docking. Sport parachutes are used by parachutists to make an accurate landing on a target, usually the center of a circle.
The basic parts of a parachute are the canopy, the suspension lines, the rip cord or other opening device, and the harness. The parachute is stored in a pack. Canopies may be shaped like circles, rectangles, hemispheres, or truncated cones, and they differ in such aerodynamic characteristics as coefficient of resistance, inflation time, and stability during descent. The area of the parachute canopy may range from 0.01 sq m to several thousand sq m. For a man-carrying parachute, an area of 40–50 sq m is adequate for a safe descent. In many cases the parachute is composed of several canopies of equal or different area. Such clusters are used as brake parachutes (three to five canopies) or landing parachutes (three to 27 canopies).
Depending on the calculated rates of descent and velocity before the parachute opens, the weight of the open parachute may reach 10 percent of the weight of the object that the parachute is designed to carry. The specific volume of the Parachute pack is usually 1.5–2.5 cu decimeters per kg of parachute weight. Canopies are made of parachute cloth that is produced from chemical fibers, for example, caprolan, nylon 66, kinol, and nomex from metallized glass fiber, and from natural silk and cotton. Parachute cloth has a high strength under static and dynamic loads and a low weight. It is wrinkle-resistant and heat-resistant.
A parachute descent begins with the opening of the pack by means of a rip cord, which may be operated either by a special semiautomatic device or manually by the parachutist (see Figure 1). The pack may also be pulled open by a line that has one end attached to the flying craft and the other to a device that opens the pack. The minimum rate of vertical descent of an object on a parachute in the air at the moment of landing is 4–5 m/sec; with a rocket braking device or powerful shock absorbers, the rate may be 1–2 m/sec. Parachutes released from aircraft can support loads ranging from 0.1 kg to several dozen tons; missile stages that are recovered by parachute may weigh up to several hundred tons.
The first scientific description of the principle behind the operation of the parachute was given by Leonardo da Vinci (1495). The first descents by parachute were made by the Venetian engineer F. Veranzio, from the roof of a high tower in 1617, and the French aeronaut A. J. Garnerin, from a balloon in 1797. In 1911 the Russian inventor G. E. Kotel’nikov created the first backpack-type emergency parachute. In the USSR major contributions to the development of parachute technology have been made by numerous designers, including O. I. Volkov, N. A. Lobanov, A. I. Privalov, and F. D. Tkachev, and by the test parachutists E. N. Andreev, V. G. Romaniuk, and O. K. Khomutov.
REFERENCESSovremennye sredstva avariinogo pokidaniia samoleta. Moscow, 1961. Brown, W. D. Parachutes. London, 1951.
N. A. LOBANOV
What does it mean when you dream about a parachute?
Parachutes obviously represent a means of escape from a dangerous situation. In a dream, a parachute could refer to our coping mechanisms, or it could refer to bailing out of a difficult predicament. Alternatively, some people sky dive for fun, so parachuting in a dream could refer to thrill-seeking or a sense of total freedom. Also note the idiom “golden parachute.”