A parachute is a device used to slow the motion of an object through an atmosphere by creating drag, or in the case of ram-air parachutes, aerodynamic lift. Parachutes are usually made out of light, strong cloth, originally silk, now most commonly nylon. Parachutes must slow an object's terminal vertical speed by a minimum 75% in order to be classified as such. Depending on the situation, parachutes are used with a variety of loads, including people, food, equipment, space capsules, and bombs.
The earliest evidence for the parachute dates back to the Renaissance period. The oldest parachute design appears in an anonymous manuscript from 1470s Renaissance Italy showing a free-hanging man clutching a cross bar frame attached to a conical canopy. As a safety measure, four straps run from the ends of the rods to a waist belt. The design is a marked improvement over another folio which depicts a man trying to break the force of his fall by the means of two long cloth streamers fastened to two bars which he grips with his hands. Although the surface area of the parachute design appears to be too small to offer effective resistance to the friction of the air and the wooden base-frame is superfluous and potentially harming, the revolutionary character of the new concept is obvious.
The modern parachute was invented in the late 18th century by Louis-Sébastien Lenormand in France, who made the first recorded public jump in 1783. Lenormand also sketched his device beforehand.
Today's modern parachutes are classified into two categories: ascending and descending canopies. All ascending canopies refer to paragliders which are built specifically to ascend and stay aloft as long as possible. Other parachutes including ram-air non elliptical are classified as descending canopies by manufacturers.
Round parachutes are purely a drag device (that is, unlike the ram-air types, they provide no lift) and are used in military, emergency and cargo applications. These have large dome-shaped canopies made from a single layer of triangular cloth gores. Some skydivers call them "jellyfish 'chutes" because of the resemblance. Modern sports parachutists rarely use this type.
The unique design characteristics of cruciform (square) parachutes decreases oscillation (its user swinging back and forth) and violent turns during descent. This technology will be used by the US Army as it replaces its current T-10 parachutes under a program called ATPS (Advanced Tactical Parachute System).
Most modern parachutes are self-inflating "ram-air" airfoils known as a parafoil that provide control of speed and direction similar to paragliders.
A parachute is carefully folded, or "packed" to ensure that it will open reliably. If a parachute is not packed properly it can result in a "malfunction" where the main parachute fails to deploy correctly or fully. In the U.S. and many developed countries, emergency and reserve parachutes are packed by "riggers" who must be trained and certified according to legal standards. Sport skydivers are always trained to pack their own primary "main" parachutes.
See also: http://en.wikipedia.org/wiki/Parachute
Source: Wikipedia (All text is available under the terms of the GNU Free Documentation License and Creative Commons Attribution-ShareAlike License.)