Editing Parachute (section)

== Types ==
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Today's modern parachutes are classified into two categories – ascending and descending canopies.<ref>{{cite web |first=Paul |last=McWilliams |title=A summary of different parachute types: Styles of canopy for skydiving |url=https://awe365.com/a-summary-of-different-parachute-types/ |access-date=5 October 2024 |archive-url=https://web.archive.org/web/20240424004321/https://awe365.com/a-summary-of-different-parachute-types/ |archive-date=24 April 2024 |date=18 March 2023 |url-status=live}}</ref> All ascending canopies refer to [[paraglider]]s, built specifically to ascend and stay aloft as long as possible.{{Cn|date=October 2024}} Other parachutes, including ram-air non-elliptical, are classified as descending canopies by manufacturers.{{Cn|date=October 2024}}

Some modern parachutes are classified as semi-rigid wings, which are maneuverable and can make a controlled descent to collapse on impact with the ground.{{Cn|date=October 2024}}

=== Round ===
[[File:USMC Paratrooper.jpg|thumb|upright|An American [[paratrooper]] using an MC1-1C series "round" parachute.]]

Round parachutes are purely a drag device (that is, unlike the ram-air types, they provide no [[lift (force)|lift]]) and are used in military, emergency and cargo applications (e.g. [[airdrop]]s). Most have large dome-shaped canopies made from a single layer of triangular cloth [[Gore (segment)|gores]]. Some skydivers call them "jellyfish 'chutes" because of the resemblance to the marine organisms. Modern sports parachutists rarely use this type.
The first round parachutes were simple, flat circulars. These early parachutes suffered from instability caused by oscillations. A hole in the apex helped to vent some air and reduce the oscillations. Many military applications adopted conical, i.e., cone-shaped, or parabolic (a flat circular canopy with an extended skirt) shapes, such as the United States Army [[T-10 parachute|T-10]] static-line parachute. A round parachute with no holes in it is more prone to oscillate and is not considered to be steerable. Some parachutes have inverted dome-shaped canopies. These are primarily used for dropping non-human payloads due to their faster rate of descent.

Forward speed (5–13&nbsp; km/h) and steering can be achieved by cuts in various sections (gores) across the back, or by cutting four lines in the back, thereby modifying the canopy shape to allow air to escape from the back of the canopy, providing limited forward speed. Other modifications sometimes used are cuts in various gores to cause some of the skirt to bow out. Turning is accomplished by forming the edges of the modifications, giving the parachute more speed from one side of the modification than the other. This gives the jumpers the ability to steer the parachute (such as the United States Army MC series parachutes), enabling them to avoid obstacles and to turn into the wind to minimize horizontal speed at [[landing]].

=== Cruciform ===
{{Update|part=section|date=March 2021|reason=The statements in the Cruciform subsection, regarding the T-11 parachute and its replacement of the T-10, are prospective toward an ambiguous point in the future and tells the reader nothing chronologically useful. Regardless, it appears the program mentioned has now been complete for several years, requiring edits to this description.}}
The unique design characteristics of cruciform parachutes decrease oscillation (its user swinging back and forth) and violent turns during descent. This technology will be used by the United States Army as it replaces its older T-10 parachutes with [[T-11 parachute]]s under a program called Advanced Tactical Parachute System (ATPS). The ATPS canopy is a highly modified version of a cross/ cruciform platform and is square in appearance. The ATPS system will reduce the rate of descent by 30 percent from {{convert|21|ft/s|m/s}} to {{convert|15.75|ft/s|m/s}}. The T-11 is designed to have an average rate of descent 14% slower than the T-10D, thus resulting in lower landing injury rates for jumpers. The decline in the rate of descent will reduce the impact energy by almost 25% to lessen the potential for injury.

=== Pull-down apex ===
[[File:C._1970s_'High_Performance'_canopy.jpg|thumb|1970s 'high performance' pull-down apex canopy, as seen in the 'round' (or really, elliptical) parachute's centre.]]
[[File:1970s 'High Performance' round elliptical.jpg|thumb|1970s 'round' elliptical showing 4 controllable turn slots, plus another, small side vent and one of 5 rear vents.]]

A variation on the round parachute is the pull-down apex parachute, invented by a Frenchman named Pierre-Marcel Lemoigne.<ref>Pierre Marcel Lemoigne, {{US patent|3228636}} (filed: November 7, 1963; issued: January 11, 1966).</ref><ref>{{cite web |first=Jean-Michel |last=Palau |url=http://jmp-pan.blogspot.com/2008/02/historique-du-parachutisme-ascensionnel_988.html |title=Historique du Parachutisme Ascensionnel Nautique |date=February 20, 2008 |access-date=October 22, 2013 |publisher=Le Parachutisme Ascensionnel Nautique |language=fr}} Includes '''photo''' of Lemoigne.</ref><ref>See also: Theodor W. Knacke, "Technical-historical development of parachutes and their applications since World War I (Technical paper A87-13776 03-03)," 9th Aerodynamic Decelerator and Balloon Technology Conference (Albuquerque, New Mexico; October 7–9, 1986) (New York, N.Y.:  American Institute of Aeronautics and Astronautics, 1986), pages 1–10.</ref> The first widely used canopy of this type was called the ''Para-Commander'' (made by the Pioneer Parachute Co.), although there are many other canopies with a pull-down apex produced in the years thereafter - these had minor differences in attempts to make a higher performance rig, such as different venting configurations. They are all considered 'round' parachutes, but with suspension lines to the canopy apex that apply load there and pull the apex closer to the load, distorting the round shape into a somewhat flattened or lenticular shape when viewed from the side. And while called ''rounds'', they generally have an elliptical shape when viewed from above or below, with the sides bulging out more than the for'd-and-aft dimension, the [[Chord (aeronautics)|chord]] (see the lower photo to the right and you likely can ascertain the difference).

Due to their lenticular shape and appropriate venting, they have a considerably faster forward speed than, say, a modified military canopy. And due to controllable rear-facing vents in the canopy's sides, they also have much snappier turning capabilities, though they are decidedly low-performance compared to today's ram-air rigs. From about the mid-1960s to the late-1970s, this was the most popular parachute design type for sport parachuting (prior to this period, modified military 'rounds' were generally used and after, ram-air 'squares' became common). Note that the use of the word ''elliptical'' for these 'round' parachutes is somewhat dated and may cause slight confusion, since some 'squares' (i.e. ram-airs) are elliptical nowadays, too.

=== Annular ===
Some designs with a pull-down apex have the fabric removed from the apex to open a hole through which air can exit (most, if not all, round canopies have at least a small hole to allow easier tie-down for packing - these aren't considered annular), giving the canopy an annular geometry. This hole can be very pronounced in some designs, taking up more 'space' than the parachute. They also have decreased horizontal drag due to their flatter shape and, when combined with rear-facing vents, can have considerable forward speed.  Truly annular designs - with a hole large enough that the canopy can be classified as ''ring-shaped'' - are uncommon.

=== Rogallo wing ===
Sport parachuting has experimented with the [[Rogallo wing]], among other shapes and forms. These were usually an attempt to increase the forward speed and reduce the landing speed offered by the other options at the time. The ram-air parachute's development and the subsequent introduction of the sail slider to slow deployment reduced the level of experimentation in the sport parachuting community. The parachutes are also hard to build.

=== Ribbon and ring ===
[[File:HiRISE image of MSL during EDL (refined).png|thumb|The [[Mars Science Laboratory]] capsule, carrying the Mars rover [[Curiosity (rover)|''Curiosity'']], descending under its supersonic disk-gap-band<ref>{{Cite book |last1=Clark |first1=Ian |last2=Tanner |first2=Christopher |title=2017 IEEE Aerospace Conference |chapter=A historical summary of the design, development, and analysis of the disk-gap-band parachute |date=2017-06-08 |chapter-url=https://ieeexplore.ieee.org/document/7943854 |pages=1–17 |doi=10.1109/AERO.2017.7943854 |isbn=978-1-5090-1613-6 |s2cid=40095390 |via=IEEE}}</ref> parachute.]]

Ribbon and ring parachutes have similarities to annular designs. They are frequently designed to deploy at [[supersonic]] speeds. A conventional parachute would instantly burst upon opening and be shredded at such speeds. Ribbon parachutes have a ring-shaped canopy, often with a large hole in the centre to release the pressure. Sometimes the ring is broken into ribbons connected by ropes to leak air even more. These large leaks lower the stress on the parachute so it does not burst or shred when it opens. Ribbon parachutes made of [[Kevlar]] are used on nuclear bombs, such as the [[B61 nuclear bomb|B61]] and [[B83 nuclear bomb|B83]].<ref>{{Cite journal| last1=Mitcheltree| first1=R| last2=Witkowski| first2=A| title=High Altitude Test Program for a Mars Subsonic Parachute| journal=American Institute of Aeronautics and Astronautics| url=http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/37615/1/05-0981.pdf| archive-url=https://web.archive.org/web/20090703083934/http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/37615/1/05-0981.pdf| url-status=dead| archive-date=2009-07-03}}</ref>

=== Ram-air ===
{{Main|Parafoil}}

The principle of the Ram-Air Multicell Airfoil was conceived in 1963 by Canadian Domina "Dom" C. Jalbert, but serious problems had to be solved before a ram-air canopy could be marketed to the sport parachuting community.<ref>{{cite book |last=Ryan |first=Charles W. |date=1975 |title=Sport Parachuting |location=Chicago |publisher=Henry Regnery Company |page=191 |isbn=0-8092-8378-6}}</ref> Ram-air parafoils are steerable (as are most canopies used for sport parachuting), and have two layers of fabric—top and bottom—connected by airfoil-shaped fabric ribs to form "cells". The cells fill with higher-pressure air from vents that face forward on the leading edge of the airfoil. The fabric is shaped and the parachute lines trimmed under load such that the ballooning fabric inflates into an airfoil shape. This airfoil is sometimes maintained by use of fabric one-way valves called ''[[Airlock (parachute)|airlocks]]''. "The first jump of this canopy (a Jalbert Parafoil) was made{{when|date=June 2020}} by International Skydiving Hall of Fame member Paul 'Pop' Poppenhager."<ref name="Ram-air">{{cite web |url=https://skydivingmuseum.org/hall-of-fame/inductee/domina-c-jalbert |title=International Skydiving Hall of Fame Member Domina C. Jalbert |access-date=6 June 2020 |author=International Skydiving Museum & Hall of Fame}}</ref>

==== Varieties ====
[[File:Ram air square.jpg|thumb|upright|A [[United States Navy]] Parachute Team "Leap Frogs" jumper landing a "square" ram-air parachute.]]

Personal ram-air parachutes are loosely divided into two varieties – rectangular or tapered – commonly called "squares" or "ellipticals", respectively. Medium-performance canopies (reserve-, [[BASE jumping|BASE]]-, canopy formation-, and accuracy-type) are usually rectangular. High-performance, ram-air parachutes have a slightly tapered shape to their leading and/or trailing edges when viewed in plan form, and are known as ellipticals. Sometimes all the taper is on the leading edge (front), and sometimes in the trailing edge (tail).

Ellipticals are usually used only by sport parachutists. They often have smaller, more numerous fabric cells and are shallower in profile. Their canopies can be anywhere from slightly elliptical to highly elliptical, indicating the amount of taper in the canopy design, which is often an indicator of the responsiveness of the canopy to control input for a given wing loading, and of the level of experience required to pilot the canopy safely.<ref>{{Cite journal |last=Dhiman, Chakraborty |date=June 2011 |title=Parachute: The aerodynamic lifting and deaccelerating device |url=https://www.researchgate.net/publication/298449819 |journal=Asian Textile Journal |issue=June 2011 |pages=65–75}}</ref>

The rectangular parachute designs tend to look like square, inflatable air mattresses with open front ends. They are generally safer to operate because they are less prone to dive rapidly with relatively small control inputs, they are usually flown with lower wing loadings per square foot of area, and they glide more slowly. They typically have a lower [[glide ratio]].

Wing loading of parachutes is measured similarly to that of aircraft, comparing exit weight to area of parachute fabric. Typical wing loading for students, accuracy competitors, and BASE jumpers is less than 5&nbsp; kg per square meter – often 0.3 kilograms per square meter or less. Most student skydivers fly with wing loading below 5&nbsp; kg per square meter. Most sport jumpers fly with wing loading between 5 and 7&nbsp; kg per square meter, but many interested in performance landings exceed this wing loading. Professional canopy pilots compete with wing loading of 10 to over 15 kilograms per square meter. While ram-air parachutes with wing loading higher than 20 kilograms per square meter have been landed, this is strictly the realm of professional test jumpers.

Smaller parachutes tend to fly faster for the same load, and ellipticals respond faster to control input. Therefore, small, elliptical designs are often chosen by experienced canopy pilots for the thrilling flying they provide. Flying a fast elliptical requires much more skill and experience. Fast ellipticals are also considerably more dangerous to land. With high-performance elliptical canopies, nuisance malfunctions can be much more serious than with a square design, and may quickly escalate into emergencies. Flying highly loaded, elliptical canopies is a major contributing factor in many skydiving accidents, although advanced training programs are helping to reduce this danger.{{Citation needed|date=March 2018}}

High-speed, cross-braced parachutes, such as the Velocity, VX, XAOS, and Sensei, have given birth to a new branch of sport parachuting called "swooping." A race course is set up in the landing area for expert pilots to measure the distance they are able to fly past the {{convert|1.5|m|ft|adj=on}} tall entry gate. Current world records exceed {{convert|180|m|ft}}.

Aspect ratio is another way to measure ram-air parachutes. Aspect ratios of parachutes are measured the same way as aircraft wings, by comparing span with chord. Low aspect ratio parachutes, i.e., span 1.8 times the chord, are now limited to precision landing competitions. Popular precision landing parachutes include Jalbert (now NAA) Para-Foils and John Eiff's series of Challenger Classics. While low aspect ratio parachutes tend to be extremely stable, with gentle stall characteristics, they suffer from steep glide ratios and a small tolerance, or "sweet spot", for timing the landing flare.

Because of their predictable opening characteristics, parachutes with a medium aspect ratio around 2.1 are widely used for reserves, BASE, and canopy formation competition.  Most medium aspect ratio parachutes have seven cells.

High aspect ratio parachutes have the flattest glide and the largest tolerance for timing the landing flare, but the least predictable openings. An aspect ratio of 2.7 is about the upper limit for parachutes. High aspect ratio canopies typically have nine or more cells. All reserve ram-air parachutes are of the square variety, because of the greater reliability, and the less-demanding handling characteristics.

=== Paragliders ===
{{main|paraglider}}
{{Unreferenced section|date=October 2021}}
[[File:Aerodyne shaolin.jpg|thumb|[[Paragliding]]]]
[[File:Apco_Starlite_26_paraglider_launch_inflating_cells_by_pulling_up_top_risers.jpg|thumb|Readying a paraglider for launch; inflating cells by pulling up top risers]]
[[File:Nas mãos do Cristo.JPG|thumb|Paragliding over ''[[Christ the Redeemer (statue)|Christ the Redeemer]]'' statue in Rio de Janeiro, Brazil, 2015]]
Paragliders - virtually all of which use ram-air canopies - are more akin to today's sport parachutes than, say, parachutes of the mid-1970s and earlier. Technically, they are ''ascending parachutes'', though that term is not used in the paragliding community, and they have the same basic airfoil design of today's 'square' or 'elliptical' sports [[parachuting]] canopy, but generally have more sectioned cells, higher aspect ratio and a lower profile. Cell count varies widely, typically from the high 20s to the 70s, while aspect ratio can be 8 or more, though aspect ratio (projected) for such a canopy might be down at 6 or so - both outrageously higher than a representative skydiver's parachute. The wing span is typically so great that it's far closer to a very elongated rectangle or ellipse than a ''square'' and that term is rarely used by paraglider pilots. Similarly, span might be ~15 m with span (projected) at 12 m. Canopies are still attached to the harness by suspension lines and (four or six) risers, but they use lockable [[carabiner]]s as the final connection to the harness. Modern high-performance paragliders often have the cell openings closer to the bottom of the leading edge and the end cells might appear to be closed, both for aerodynamic streamlining (these apparently closed end cells are vented and inflated from the adjacent cells, which have venting in the cell walls).

The main difference is in paragliders' usage, typically longer flights that can last all day and hundreds of kilometres in some cases. The harness is also quite different from a parachuting harness and can vary dramatically from ones for the beginner (which might be just a bench seat with nylon material and webbing to ensure the pilot is secure, no matter the position), to seatboardless ones for high altitude and [[Cross-country flying|cross-country flights]] (these are usually full-body cocoon- or hammock-like devices to include the outstretched legs - called ''speedbags'', ''aerocones'', etc. - to ensure aerodynamic efficiency and warmth). In many designs, there will be protection for the back  and shoulder areas built-in, and support for a reserve canopy, water container, etc. Some even have windshields.

Because paragliders are made for foot- or ski-launch, they aren't suitable for terminal velocity openings and there is no slider to slow down an opening (paraglider pilots typically start with an ''open'' but uninflated canopy). To launch a paraglider, one typically spreads out the canopy on the ground to closely approximate an open canopy with the suspension lines having little slack and less tangle - see more in [[Paragliding]]. Depending on the wind, the pilot has three basic options: 1) a running forward launch (typically in no wind or slight wind), 2) a standing launch (in ''ideal'' winds) and 3) a reverse launch (in higher winds). In ideal winds, the pilot pulls on the top risers to have the wind inflate the cells and simply eases the brakes down, much like an aircraft's flaps, and takes off. Or if there is no wind, the pilot runs or skis to make it inflate, typically at the edge of a cliff or hill. Once the canopy is above one's head, it's a gentle pull down on both toggles in ideal winds, a tow (say, behind a vehicle) on flat ground, a continued run down the hill, etc. Ground handling in a variety of winds is important and there are even canopies made strictly for that practice, to save on wear and tear of more expensive canopies designed for say, [[Cross-country flying|XC]], competition or just recreational flying.

==== General characteristics ====
Main parachutes used by [[skydiver]]s today are designed to open softly. Overly rapid deployment was an early problem with ram-air designs. The primary innovation that slows the deployment of a ram-air canopy is the [[slider (parachuting)|slider]]; a small rectangular piece of fabric with a [[grommet]] near each corner. Four collections of lines go through the grommets to the risers (risers are strips of webbing joining the harness and the rigging lines of a parachute). During deployment, the slider slides down from the canopy to just above the risers. The slider is slowed by air resistance as it descends and reduces the rate at which the lines can spread. This reduces the speed at which the canopy can open and inflate.

At the same time, the overall design of a parachute still has a significant influence on the deployment speed. Modern sport parachutes' deployment speeds vary considerably. Most modern parachutes open comfortably, but individual skydivers may prefer harsher deployment.

The deployment process is inherently chaotic. Rapid deployments can still occur even with well-behaved canopies. On rare occasions, deployment can even be so rapid that the jumper suffers bruising, injury, or death. Reducing the amount of fabric decreases the air resistance.  This can be done by making the slider smaller, inserting a mesh panel, or cutting a hole in the slider.