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.
Some modern parachutes are classified as semi-rigid wings, which are maneuverable and can make a controlled descent to break on impact with the ground.
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 US Army 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.
A large (3-8 mph) forward speed and steering can be achieved by cuts in various sections (gores) across the back, or by cutting 4 lines in the back thereby modifying the canopy to allow air to escape from the back of the canopy, providing limited forward speed. Modifications can skirt bow out.[clarification needed] 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, enabling them to avoid obstacles and to turn into the wind to minimize horizontal speed at jumping.
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 less-efficient glide ratio.
Wing loading of parachutes is measured similarly to that of aircraft: comparing the number of pounds (exit weight) to square footage of parachute fabric. Typical wing loadings for students, accuracy competitors, and BASE jumpers are less than one pound per square foot—often 0.7 pounds per square foot or less. Most student skydivers fly with wing loadings below one pound per square foot. Most sport jumpers fly with wing loadings between 1.0 and 1.4 pounds per square foot, but many interested in performance landings exceed this wing loading. Professional Canopy pilots compete at wing loadings of 2 to 3+ pounds per square foot. While ram-air parachutes with wing loadings higher than four pounds per square foot 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.
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 5-foot (1.5 m) tall entry gate. Current world records exceed 600 feet (180 m).
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 small "sweet spots" for timing the landing flare.
Medium aspect ratio (i.e. 2.1) parachutes are widely used for reserves, BASE, and canopy formation competition because of their predictable opening characteristics. Most medium aspect ratio parachutes have seven cells.
High aspect ratio parachutes have the flattest glide and the largest "sweet spots" (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.
Some modern parachutes are classified as semi-rigid wings, which are maneuverable and can make a controlled descent to break on impact with the ground.
Round types
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 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 US Army 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.
A large (3-8 mph) forward speed and steering can be achieved by cuts in various sections (gores) across the back, or by cutting 4 lines in the back thereby modifying the canopy to allow air to escape from the back of the canopy, providing limited forward speed. Modifications can skirt bow out.[clarification needed] 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, enabling them to avoid obstacles and to turn into the wind to minimize horizontal speed at jumping.
Technical
or Specification
Approximate Parachute Sizes for a
Rocket Weighing 120 kilograms:
Descent
Rate |
Diameter
|
||
3 mps
|
19.37 m
|
||
4 mps
|
14.27 m
|
||
5 mps
|
|
||
6 mps
|
9.51 m
|
The above sizes are estimates based
on a parachute with a drag coefficient of 0.75.
You may use the form below to
calculate the parachute size for another rocket.
Parachute size calculator http://www.rocketreviews.com/parachute-size-calculator.html
Minimum height for jump: 400feet/122m
above ground level
Ram-air (square) types
Most modern parachutes are self-inflating "ram-air" airfoils known as a parafoil that provide control of speed and direction similar to paragliders. Paragliders have much greater lift and range, but parachutes are designed to handle, spread and mitigate the stresses of deployment at terminal velocity. All ram-air parafoils have two layers of fabric; top and bottom, connected by airfoil-shaped fabric ribs to form "cells." The cells fill with high 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 Airlocks. The first Ram-air test jump was made by Navy test jumper Joe Crotwell.
General
characteristics of ram-airs
Main parachutes used by skydivers 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; 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.
Technical
or Specification
Size
Sq. m.
|
Length
In
ft
|
Length
in meter
|
Breadth
in
ft
|
Breadth
in meter
|
Maximum
Exit Weight Recommended in kg
|
Aspect
Ratio
|
17.52
|
21.8
|
6.64
|
8.7
|
2.64
|
85.73
|
2.5
|
19.40
|
22.9
|
6.98
|
9.1
|
2.78
|
94.80
|
2.5
|
22.18
|
24.5
|
7.47
|
9.7
|
2.97
|
108.41
|
2.5
|
24.04
|
25.5
|
7.78
|
10.1
|
3.09
|
117.48
|
2.5
|
25.90
|
26.5
|
8.07
|
10.5
|
3.21
|
126.55
|
2.5
|
27.72
|
27.4
|
8.35
|
10.9
|
3.32
|
135.62
|
2.5
|
SPECIFICATIONS
|
|
Max Speed
|
150 keas / 278 kph
|
Max Altitude
|
20000ft / 6096m A.S.L
|
Max Weight
|
250 lbs / 114 kg
|
Glide Ratio
|
3.0:1
|
Minimum Height for jump
|
800ft/243.84m
|
SIZE
In sq ft/m
|
LENGTH
Ft/m
|
BREADTH
Ft/m
|
ASPECT
|
VOLUME
|
MAX. WEIGHT
|
170 /15.6
|
19.8 /6.0
|
8.6 /2.6
|
2.3
|
473
|
86
kg’s / 50 kg’s Student
|
185 /16.74
|
20.6 /6.2
|
8.9 /2.7
|
2.3
|
482
|
93
kg’s / 55 kg’s Student
|
200 /18.54
|
21.45/6.53
|
9.33 /2.84
|
2.3
|
516
|
100 kg’s / 60
kg’s Student
|
230 /21.28
|
23 /7.0
|
10 /3.04
|
2.3
|
580
|
105 kg’s / 70
kg’s Student
|
260 /23.99
|
24.4 /7.43
|
10.6 /3.23
|
2.3
|
600
|
109 kg’s
|
290 /26.91
|
27.6 /8.41
|
10.5 /3.2
|
2.6
|
627
|
114 kg’s (250
Lbs)
|
Varieties of personal ram-airs
Personal ram-air parachutes are loosely divided into two varieties: rectangular or tapered, commonly referred to as "squares" or "ellipticals" respectively. Medium-performance canopies (reserve-, 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 in the leading edge (front), and sometimes in the trailing edge (tail). Ellipticals are usually used only by sports parachutists. Ellipticals 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.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 less-efficient glide ratio.
Wing loading of parachutes is measured similarly to that of aircraft: comparing the number of pounds (exit weight) to square footage of parachute fabric. Typical wing loadings for students, accuracy competitors, and BASE jumpers are less than one pound per square foot—often 0.7 pounds per square foot or less. Most student skydivers fly with wing loadings below one pound per square foot. Most sport jumpers fly with wing loadings between 1.0 and 1.4 pounds per square foot, but many interested in performance landings exceed this wing loading. Professional Canopy pilots compete at wing loadings of 2 to 3+ pounds per square foot. While ram-air parachutes with wing loadings higher than four pounds per square foot 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.
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 5-foot (1.5 m) tall entry gate. Current world records exceed 600 feet (180 m).
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 small "sweet spots" for timing the landing flare.
Medium aspect ratio (i.e. 2.1) parachutes are widely used for reserves, BASE, and canopy formation competition because of their predictable opening characteristics. Most medium aspect ratio parachutes have seven cells.
High aspect ratio parachutes have the flattest glide and the largest "sweet spots" (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.
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