Science Fair Project Encyclopedia
A parachute is a soft fabric device used to slow the motion of an object through an atmosphere by creating drag. Parachutes are generally used to slow the descent of a person or object to Earth or another celestial body with an atmosphere. Parachutes are also sometimes used to aid horizontal deceleration of a vehicle (an airplane or space shuttle after touchdown, or a drag racer). The word parachute comes from the French words para, protect or shield, and chute, to fall. Therefore parachute actually means to protect from a fall. Many types of modern parachute are quite maneuverable, and can be flown like gliders.
Parachutes were once made from silk but these days are almost always constructed from more durable woven nylon fabrics.
A few medieval documents record the use of parachute-like devices to allow a person to fall (somewhat) safely from a height. In 852, an Andalusian daredevil named Armen Firman jumped from a tower in Cordoba using a loose cloak stiffened with wooden struts to arrest his fall, sustaining only minor injuries. In 1178, another Muslim attempted a similar feat in Constantinople, but he broke several bones and later died of his injuries. According to Joseph Needham there were working parachutes in China as early as the twelfth century.
Leonardo da Vinci sketched a parachute while he was living in Milan around 1485. However, the idea of the parachute may not have originated with him: the historian Lynn White has discovered an anonymous Italian manuscript from about 1470 that depicts two designs for a parachute, one of which is very similar to da Vinci's. The first known test of such a parachute was made in 1617 in Venice by the Croatian inventor Faust Vrančić. A 1595 sketch of Vrančić's parachute is at left.
The parachute was re-invented in 1783 by Sebastien Lenormand in France. Lenormand also coined the name parachute. Two years later, Jean-Pierre Blanchard demonstrated it as a means of safely disembarking from a hot air balloon. While Blanchard's first parachute demonstrations were conducted with a dog as the passenger, he later had the opportunity to try it himself when in 1793 his hot air balloon ruptured and he used a parachute to escape.
Subsequent development of the parachute focused on it becoming more compact. While the early parachutes were made of linen stretched over a wooden frame, in the late 1790s, Blanchard began making parachutes from folded silk, taking advantage of silk's strength and light weight. In 1797, Andrew Garnerin made the first jump using such a parachute. Garnerin also invented the vented parachute, which improved the stability of the fall. In 1890, Paul Letteman and Kathchen Paulus made the first knapsack parachute.
Paratroopers are soldiers who arrive in enemy territory by parachutes.
Most space vehicles descend to Earth using several parachutes. The pair of reusable solid-fuel rocket boosters (SRB) of the Space Shuttle have parachutes; they are recovered after falling to the ocean. Some exploration rovers (such as NASA's Spirit and ESA's Beagle 2) descend to their target destination with parachutes.
Food aid packages are sometimes delivered by parachute.
Parachutes can also be deployed from a jet aircraft horizontally from the tail cone at the point of touchdown or shortly afterwards to shorten its landing run, for example if landing on an aircraft carrier or with a tailwind, or on a relatively short runway. The parachute will normally be jettisoned after the aircraft has slowed to taxiing speed and then retrieved by ground crew. This technique reduces the chance of it becoming entangled with the airframe once it has ceased to be deployed in its functional, hemispherical shape. A similar parachute is used to slow drag racers, and the Space Shuttle after its runway touchdown.
Jet fighter ejector seats are equipped with automatically deployed parachutes.
A paraglider with a motor and possibly wheels is called a powered parachute or, sometimes, a paraplane.
A parachute is made from thin, lightweight fabric, support tapes and shroud lines. The lines are usually gathered through loops or rings at several strong straps called risers. The risers directly strap the item or person being supported, called the "load." Parachutes are pulled out of their packages by a smaller parachute called a drogue or "pilot 'chute." Pilot chutes usually have a large spring that pushes them into the air-stream, or forces them open. The pilot 'chute is released by a cable called a "rip cord." Usually the rip cord pulls a metal pin that releases fabric flaps that hold the pilot 'chute in a compact package. Pilot 'chutes may be released by a "static line." The static line is a length of string clipped to the airplane. In some sport parachutes and some emergency parachutes, the rip cord is a manual device, a "T" (pronounced "tee") handle attached to the chest straps. Emergency parachutes have the "T" handle when the designer cannot know when to release the parachute. Cargo parachutes are always released by static lines. Paratroop chutes are also usually released by static lines.
Paratroopers and sport skydivers carry two parachutes. The primary parachute is larger, with a lower landing speed or a gliding parasail. The second, "reserve parachute" is smaller, and quicker-opening with a manual rip cord. The jumper uses the emergency chute if the primary parachute fails to open. Reserve parachutes were introduced in World War II by the US Airborne Unit, and are now universal.
There are several types of parachutes in common use. Ribbon and ring parachutes can be designed to open at speeds as high as Mach 2 (two times the speed of sound). These have a ring-shaped canopy, often with a large hole in the center to release the pressure. Sometimes the ring is broken into ribbons connected by ropes to leak air even more. The large leaks lower the stress on the parachute so it does not burst when it opens.
Often a high speed parachute slows a load down and then pulls out a lower speed parachute. The mechanism to sequence the parachutes is called a "delayed release" or "pressure detent release" depending on whether it releases based on time, or the reduction in pressure as the load slows down.
Emergency parachutes and cargo parachutes designed to go straight down are pure drag devices. These have large dome-shaped canopies made from a single layer of cloth. Some skydivers call them "jellyfish 'chutes" because they look like dome-shaped jellyfish. Some dome parachutes can be steered by flaps. They usually have a small hole the center of the dome to spill air, so that the parachute does not have to swing to spill air from its edges.
Most modern parachutes are self-inflating "ram-air" wings that provide control of speed and direction similar to the related paragliders. (Purists in either sport would note that paragliders have much greater lift and range, but that parachutes are designed to absorb the stresses of deployment at terminal velocity.) Parasails are parachutes that are like inflatable wings. They have two layers of fabric, connected by shaped fabric gores. The space between the two fabric layers fills with high pressure air from vents that face forward. The gores are cut in the cross-section of a wing, so that they pull the ballooning fabric into an inflated wing-shape.
Parasails divide into two further types. High speed parasails are shaped like an ellipse. Usually their vents are small triangular scoops on the underside, pulled open by lines. Low-speed parasails look much like square inflatable air-mattresses with open front ends. Ellipticals move faster, but this is not always an advantage, because it makes the parachute harder to fly, and more dangerous to land. In the early days, some ellipticals opened and inflated less reliably than low-speed parasails, but reliable makes of parachute have resolved these problems.
Powered parachutes are a form of ultralight aircraft, generally employing rectangular dual surface parafoil wings with open cells on the leading edge of the wing. A go-cart like frame is used to mount the pilot seat and engine, creating a stable flying platform that is very easy to fly in calm weather conditions.
Sport parachutes used by skydivers today are designed to open softly. Modern sport parachutes rarely create strap bruises from the opening shock. Emergency parachutes almost always do.
A parachute is carefully folded, or "packed" to assure that it will open reliably. In the U.S. and many developed countries, emergency parachutes are packed by "riggers" who must be trained and certified according to legal standards. Paratroops and sport skydivers are always trained to pack their own primary parachutes.
Parachutes can malfunction in several ways. Malfunctions can range from minor problems that can be corrected in-flight and still landed to catastrophic malfunctions that require the main parachute to be released and a second parachute called a reserve to be deployed. Most skydivers are also equipped with small barometric computers (known as AAD or Automatic Activation Device like Cypres, FXC or Vigil) that can deploy the reserve parachute if the skydiver himself is unable or has not done so at a preset altitude and decent rate.
About 1 in 1000 hundred main parachute openings malfunction. Reserve parachutes are designed and packed differently and are far more reliable. In the U.S., the average fatality rate is considered to be about 1 in 80,000 jumps. Most injuries and fatalities in sport skydivng occur under a fully functional main parachute and because the skydiver performed unsafe maneuvers.
The average skydiver in the U.S. makes about 150 jumps per year and will leave the sport before the 5th year.
- Hang glider
- Ultralight aviation
- Freefall (accidents of failed or missing parachute)
- USPA The United States Parachute Association -- The governing body for sport skydiving in the U.S.
- Dropzone.com the Premier web resource for information on Skydiving, Dropzones and modern parachuting
- National Parachute Test Center - Part of NAF El Centro located near El Centro,California.
- Charity Parachute Jumps Experience skydiving, parachuting and tandem jumps across the UK by raising money for disabled children.
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