Parachutes

by Chris Woodford . Last updated: May 13, 2021.

Y ou’re screaming through the sky, safely tucked up in the cockpit of a jet fighter, when there’s a sudden loud bang and the engine judders to a halt. Well that’s just great, isn’t it? Here you are zooming along at maybe 2000 km/h (1200mph), several kilometers/miles above the ground and your plane has chosen this exact moment to break down! What do you do? Eject as soon as you possibly can, wait for the plane to fly clear, and then hit your parachute . With luck, you glide safely to the ground and live to fly another day. When it comes to saving lives, parachutes are among the simplest and most effective of inventions. How exactly do they work? Let’s take a closer look!

Photo: A traditional round parachute. Although military paratroopers still use them, they are now largely obsolete for recreational diving. Photo by Chris Desmond courtesy of US Navy.

Contents

  1. How does a parachute work in theory?
    • What causes air resistance?
    • Terminal velocity
    • How much does a parachute slow you down?
  2. What shape are parachutes?
  3. What are the parts of a traditional, round parachute?
  4. How does a parachute work in practice?
    • Softer landings
  5. Find out more

How does a parachute work in theory?

Photo: Square-shaped “ram-air” parachutes are much more common than round parachutes because they’re easier to steer and control. Photo by Shannon K. Cassidy courtesy of US Navy.

Throw a ball up in the air and, sooner or later, it always falls back to the ground. That’s because Earth pulls everything toward it with a force called gravity. You’ve probably learned in school that the strength of Earth’s gravity is roughly the same all over the world (it does vary a little bit, but not that much) and that if you drop a heavy stone and a light feather from the top of a skyscraper, gravity pulls them toward the ground at exactly the same rate.

If there were no air, the feather and the stone would hit the ground at the same time. In practice, the stone reaches the ground much faster, not because it weighs more but because the feather fans out and catches in the air as it falls. Air resistance (also called drag) slows it down.

Photo: Parachutes are made from strong lightweight nylon and have to be packed very carefully if they’re to open correctly when they’re deployed. Photo by Gary Ward courtesy of US Navy.

What causes air resistance?

Just because the air’s invisible, doesn’t mean it’s not there. Earth’s atmosphere is packed full of gas molecules, so if you want to move through air—by walking, in a car, in a plane, or dangling from a parachute—you have to push them out of the way. We only really notice this when we’re moving at speed.

Air resistance is a bit like the way water pushes against your body when you’re in a swimming pool—except that air is invisible! If you jump off a diving board or do a belly flop, the awkward shape of your body will create a a lot of resistance and bring you rapidly to a halt when you crash into the water. But if you make a sharp pointed shape with your arms and dive in gracefully, your body will part the water cleanly and you’ll continue to move quickly as you enter it. When you jump or belly flop, your body slows down quickly because the water can’t get out of the way fast enough. When you dive, you part the water smoothly in front of you so your body can glide through it quickly. With parachutes, it’s the slowing-down effect that we want.

If you fall from a plane without a parachute, your relatively compact body zooms through the air like a stone; open your parachute and you create more air resistance, drifting to the ground more slowly and safely—much more like a feather. Simply speaking, then, a parachute works by increasing your air resistance as you fall.

Terminal velocity

When a force pulls on something, it makes that object move more quickly, causing it to gain speed. In other words, it causes the object to accelerate. Like any other force, gravity makes falling objects accelerate—but only up to a point.

If you jump out of a plane, your body ought to speed up by 10 meters per second (32ft per second) every single second you’re falling. We call that an acceleration of 10 meters per second per second (or 10 meters per second squared, for short, and write it like this: 10m/s/s or 10m/s 2 ). If you were high enough off the ground, then after about a minute and a half (let’s say 100 seconds), you’d theoretically be falling at about 1000 meters per second (3600km/h or 2200 mph), which is about as fast as the fastest jet fighters have ever flown!

Artwork: When you reach terminal velocity, the upward force of air resistance exactly balances the downward pull of gravity and you stop accelerating.

In practice, that simply doesn’t happen. After about 12 seconds, you reach a speed where the force of air resistance (pushing you upward) increases so much that it balances the force of gravity (pulling you downward). At that point, there is no net acceleration and you keep on falling at a steady speed called your terminal velocity . Unfortunately, the terminal velocity for a falling person (with arms stretched out in the classic freefall position) is about 55 meters per second (200km/h or 125 mph), which is still plenty fast enough to kill you—especially if you’re falling from a plane!

Photo: 1) Freefall in theory: In this training exercise, the skydiver is practicing freefall by floating over a huge horizontally mounted air fan. The force of the air pushing upward is exactly equal to the diver’s weight pulling him downward so he floats in mid-air. Photo by Gary L. Johnson courtesy of US Navy.

Photo: 2) Freefall in practice: In reality, it’s not the air that moves past you—you move through the air—but the physics is still the same: once you reach terminal velocity, the force of the air on your body pushing you upward exactly equals the force of gravity pulling you down. Photo by Ashley Myers courtesy of US Navy.

How much does a parachute slow you down?

Feathers fall more slowly than stones because their terminal velocity is lower. So another way of understanding how a parachute works is to realize that it dramatically lowers your terminal velocity by increasing your air resistance as you fall. It does that by opening out behind you and creating a large surface area of material with a huge amount of drag. Parachutes are designed to reduce your terminal velocity by about 90 percent so you hit the ground at a relatively low speed of maybe 5–6 meters per second (roughly 20 km/h or 12 mph)—ideally, so you can land on your feet and walk away unharmed.

What shape are parachutes?

Photo: Paratroopers often still use round chutes because they’re an effective way to get lots of people quickly and safely to the ground in a fairly small space. This parachute drop took place in Latvia in June 2018. Photo by Gina Danals courtesy of US Navy.

Traditionally, parachutes were round (dome-shaped) and, with their dangling suspension lines, looked a bit like jellyfish as they fell. They had vent holes that allowed air to escape, which helped to prevent them from rocking about as they came down, and their lines provided very basic steering. Most modern parachutes are rectangular (a design known as ram-air ). They have a number of cells that inflate as the air “rams” into them, so they form a fairly rigid, curved airfoil wing, which is much more steerable and controllable than a dome-shaped parachute. Round chutes are still widely used by military paratroopers, because they work well for dropping lots of people together, in a fairly small area, at relatively low altitudes; paratroopers are simply trying to get to the ground quickly, not show off their skydiving technique. Recreational divers, on the other hand, consider round chutes obsolete: virtually all of them now use the ram-air design instead.

What are the parts of a traditional, round parachute?

If you’ve ever seen a parachute spread out on the ground, you’ll know it has lots of separate parts, and it can be a very tricky thing to pack back into its container so it opens correctly next time. What are all the bits and what do they do? Here are some of the more important ones, but there are quite a few more that I’ve missed out for clarity.

  1. Pilot chute: A small parachute that opens the large, main parachute.
  2. Bridle: Connects the pilot chute to the main chute.
  3. Apex or top vent: Allows a slow escape of air from the top of the main chute. This prevents air from leaking out of the sides of the canopy, which tends to rock the parachute wildly as it falls.
  4. Canopy: Main part of the parachute.
  5. Skirt: Lower part of the canopy (think of a person’s skirt hanging down).
  6. Suspension lines: Spread the weight of the parachutist evenly across the canopy.
  7. Links: Connect the suspension lines to the risers.
  8. Risers: Connect the links to the harness
  9. Control lines: I’ve drawn only one, but there can be several different ones for steering and braking.
  10. Harness and container: The harness is the part you wear (itself made of numerous components); the container looks similar to a rucksack and holds the packed-up parachute and all its bits and pieces, ready for action!

How does a parachute work in practice?

Skydivers make parachuting look easy, but it’s all a bit more tricky in practice! What you’re trying to achieve is to get a large piece of super-strong material opening out above and behind you in a perfectly uniform way when you’ve just jumped from a plane screaming along maybe ten times faster than a race car! How can you possibly pull something safely behind you under those conditions?

Parachutes are actually three chutes in one, packed into a single backpack called the container . There’s a main parachute, a reserve parachute (in case the main one fails), and a tiny little chute at the bottom of the container, called the pilot chute , that helps the main chute to open. Once you’re clear of the plane, you trigger the pilot chute (either by pulling on a ripcord or simply by throwing the pilot chute into the air). It rapidly opens up behind you, creating enough force to tug the main chute from the container. The main chute has to be carefully packed so the ropes that connect it to your harness (known as suspension lines ) open correctly and straighten out behind you. The main chute is designed to open in a delayed way so your body isn’t braked and jerked too suddenly and sharply. That’s safer and more comfortable for you and it also reduces the risk of the parachute ripping or tearing.

The force on a parachute is considerable, so it has to be made from really strong materials. Originally, parachutes were made from canvas or silk, but inexpensive, lightweight, synthetic materials such as nylon and Kevlar® (a chemical relative of nylon) are now generally used instead.

Softer landings

Parachutes were invented about a century ago, but they continue to evolve, as inventors devise ever-better ways to improve their safety and handling. Here’s a more advanced ‘chute, designed for the US Army in 2001 (and patented in 2003). It contains the same basic features as other chutes: a canopy (10, blue), a skirt underneath (12), and suspension lines (14) in four groups called risers (16), attached to a bridle (22), which supports the harness (26) and parachutist (P). But it also has two improved safety features to reduce the risk of the parachutist landing too fast and too hard. At the top, the parachute has a bridle with an extra loop of rope on either side and an electrical cutting mechanism to release it (pink, top, labeled 28). In the middle, it has what’s known as a pneumatic muscle (bright green, 24). There’s an altitude measuring device (gray, top, 34, 36, 44), which projects radar beams to the ground to measure your height and speed and figure out when the safety mechanisms need to be deployed.

How does it work? That’s shown in the artwork on the right. If the wind blows you too fast horizontally, the appropriate electrical mechanism releases one of the extra side ropes, causing the parachute to tilt to the opposite side, so reducing your speed. When you near the ground, if you’re going too fast, the pneumatic muscle shortens, pulling you much closer toward the canopy, and so reducing your speed.

What a drag!

Photo: The Space Shuttle Endeavour, coming in to land on June 19, 2002. Photo courtesy of NASA Armstrong Flight Research Center.

Using a parachute to bring a person safely to the ground from a plane is one thing. But what if you had to bring an entire plane to rest the same way? That was the challenge facing NASA every time the Space Shuttle (the reusable space plane, now-retired) came back to Earth.

During its launch phase, the Shuttle had a powerful main engine and rocket boosters to power it into space. But when it came back again, it was nothing but a glider, drifting through the air and counting on its stubby wings to carry it home.

Once it was safely back inside Earth’s atmosphere, the Shuttle hit its 4.5km (2.8mile) long landing strip at about 350km/h (220mph)—rather faster than a typical jet airplane (which lands at speeds more like 240km/h or 150mph). When the wheels were on the ground, the crew applied the brakes to bring the craft safely to a halt, but they also used a horizontal parachute called a drag chute to help. It was about 12m (40ft) across and helped to cut the Shuttle’s speed by about 75 percent before it was jettisoned.

How Do Parachutes Slow You Down?

How do parachutes slow you down? Does your weight affect your speed? How does it feel when your parachute opens?

When you sign up for a skydive you are putting a lot of faith in the team, instructors, and equipment. Skydiving is incredibly safe. In fact, you are 24 times more likely to have a serious car accident on the way to the skydive. But it’s natural to have questions about how it all works…

Let’s break it down and have a look at how parachutes slow you down and bring you safely back to the ground.

How does a parachute slow you down?

skydiving over mountain

Parachutes slow down your terminal velocity

On a skydive, you will actually have 3 parachutes in your backpack: the main parachute, the pilot chute (a small parachute that helps open the main parachute), and the reserve (activated in an emergency). The pilot chute is the first to deploy, which creates the force to open up the main parachute. The main chute is designed to then open up in such a way that it doesn’t jerk the skydiver but opens smoothly.

Once the main parachute opens it creates a large surface area above you, creating a lot of drag force. This immediately reduces your terminal velocity and slows down your descent; a skydiver in freefall has a terminal velocity (maximum speed) of around 120 MPH, but with an open parachute above you that speed will reduce to just 10 to 20 MPH.

While parachutes are made out of lightweight nylon or Kevlar, once open they are incredibly strong. An open parachute gliding you to the earth is so stiff and strong that someone could safely walk across the top.

How does a parachute work?

teacher in school

How exactly do parachutes work?

Parachutes are all designed to slow you down. An open parachute uses its large surface area to create drag or air resistance. The design of the parachutes and their cords allow for the parachute to unfold in a way that quickly traps air inside it.

By forcing air into the underside of the parachute it creates a wing structure under the canopy. As well as reducing the terminal velocity of the skydiver to a very safe 10-20 MPH. Modern parachutes are also designed for maneuverability. Using the steering lines the skydiver can change the shape of the wings and turn. These can also be used to increase and decrease the speed at which you drop.

You may have seen old footage of circular-looking parachutes but modern parachutes are actually rectangular. This new design gives skydivers much greater control over their descent.

Do heavier skydivers fall faster?

freefalling

Who falls faster?

Yes, it’s possible that a heavy skydiver would fall faster than a much lighter skydiver. But weight isn’t the defining factor over how fast we fall.

Weight actually makes a much smaller difference than you think. Try dropping a heavy object and a much lighter object of the same shape and size, and you may not notice which one falls fastest. But if you drop two pieces of paper at the same time, one flat and one rolled into a ball, the ball will fall much fast. This is because drag and air resistance make a big difference.

If two people of similar surface areas jump from a plane and one weighs 10kg more, they would fall at very similar speeds. But if one of those people curled their falling body into a ball, and the other spread their body wide, the person curled up would fall much faster.

This is why, regardless of your weight, a large canopy open above you will slow you down significantly. Try it for yourself with a freefall calculator. Changing the weight of an object makes only a minute difference to the terminal velocity. While changing the size and surface area can make a huge difference.

Do you go up when you open a parachute?

jumping from plane

Do parachutes lift you up briefly?

When parachutes are deployed they slow you down a safe speed. However, it still creates a very quick shift in terminal velocity. As the chute unfolds and creates significantly more air resistance, your speed reduces by around 100 MPH within a few seconds. But at no time would the parachute actually lift you up!

Such is the significant decrease in speed that it may feel like you are lifting for a brief moment. And if you see video footage of skydivers pulling their parachutes, it may also look like they are suddenly lifting up. This is usually because the camera shot or camera person is still moving down at the original speed, but the skydivers’ speed suddenly slows.

How late can you open a parachute?

skydiving landing

First-time skydivers open their parachute by 4,00 feet above ground

You have probably heard about base jumpers leaping from heights of 500 feet, 300 feet, even sub 200 feet! While it is possible to successfully deploy a parachute at these crazy low heights, that isn’t the norm! Base jumpers use very specific parachute designs and systems, and for skydivers, there are strict minimum heights. Safety is paramount!

The United States Parachute Association (USPA) lays out very clear guidelines on the minimum heights a parachute should be deployed. The minimum height recommended for you is based on your experience and expertise:

Novices and new students are required to deploy their parachutes by 4,000 feet above ground level.

Beginners (skydivers holding an ‘A’ license) must deploy their parachute by 3,500 feet above ground level.

Intermediate skydivers (holding a ‘B’ license) must deploy their parachutes by 3,000 feet.

Accomplished skydivers (holding ‘C’ or ‘D’ licenses) are recommended to deploy their parachutes by 2,500 feet. However, it is acceptable for more professional skydivers to drop to as low as 2,000 feet before deployment.

The absolute minimum height for safely deploying a parachute is considered to be 1,000 feet. This is strictly only recommended in emergencies, such as when being ejected from an aircraft; aircraft emergency parachutes are designed to open much faster.

How Do Parachutes Slow You Down?

How do parachutes slow you down? Does your weight affect your speed? How does it feel when your parachute opens?

When you sign up for a skydive you are putting a lot of faith in the team, instructors, and equipment. Skydiving is incredibly safe. In fact, you are 24 times more likely to have a serious car accident on the way to the skydive. But it’s natural to have questions about how it all works…

Let’s break it down and have a look at how parachutes slow you down and bring you safely back to the ground.

How does a parachute slow you down?

skydiving over mountain

Parachutes slow down your terminal velocity

On a skydive, you will actually have 3 parachutes in your backpack: the main parachute, the pilot chute (a small parachute that helps open the main parachute), and the reserve (activated in an emergency). The pilot chute is the first to deploy, which creates the force to open up the main parachute. The main chute is designed to then open up in such a way that it doesn’t jerk the skydiver but opens smoothly.

Once the main parachute opens it creates a large surface area above you, creating a lot of drag force. This immediately reduces your terminal velocity and slows down your descent; a skydiver in freefall has a terminal velocity (maximum speed) of around 120 MPH, but with an open parachute above you that speed will reduce to just 10 to 20 MPH.

While parachutes are made out of lightweight nylon or Kevlar, once open they are incredibly strong. An open parachute gliding you to the earth is so stiff and strong that someone could safely walk across the top.

How does a parachute work?

teacher in school

How exactly do parachutes work?

Parachutes are all designed to slow you down. An open parachute uses its large surface area to create drag or air resistance. The design of the parachutes and their cords allow for the parachute to unfold in a way that quickly traps air inside it.

By forcing air into the underside of the parachute it creates a wing structure under the canopy. As well as reducing the terminal velocity of the skydiver to a very safe 10-20 MPH. Modern parachutes are also designed for maneuverability. Using the steering lines the skydiver can change the shape of the wings and turn. These can also be used to increase and decrease the speed at which you drop.

You may have seen old footage of circular-looking parachutes but modern parachutes are actually rectangular. This new design gives skydivers much greater control over their descent.

Do heavier skydivers fall faster?

freefalling

Who falls faster?

Yes, it’s possible that a heavy skydiver would fall faster than a much lighter skydiver. But weight isn’t the defining factor over how fast we fall.

Weight actually makes a much smaller difference than you think. Try dropping a heavy object and a much lighter object of the same shape and size, and you may not notice which one falls fastest. But if you drop two pieces of paper at the same time, one flat and one rolled into a ball, the ball will fall much fast. This is because drag and air resistance make a big difference.

If two people of similar surface areas jump from a plane and one weighs 10kg more, they would fall at very similar speeds. But if one of those people curled their falling body into a ball, and the other spread their body wide, the person curled up would fall much faster.

This is why, regardless of your weight, a large canopy open above you will slow you down significantly. Try it for yourself with a freefall calculator. Changing the weight of an object makes only a minute difference to the terminal velocity. While changing the size and surface area can make a huge difference.

Do you go up when you open a parachute?

jumping from plane

Do parachutes lift you up briefly?

When parachutes are deployed they slow you down a safe speed. However, it still creates a very quick shift in terminal velocity. As the chute unfolds and creates significantly more air resistance, your speed reduces by around 100 MPH within a few seconds. But at no time would the parachute actually lift you up!

Such is the significant decrease in speed that it may feel like you are lifting for a brief moment. And if you see video footage of skydivers pulling their parachutes, it may also look like they are suddenly lifting up. This is usually because the camera shot or camera person is still moving down at the original speed, but the skydivers’ speed suddenly slows.

How late can you open a parachute?

skydiving landing

First-time skydivers open their parachute by 4,00 feet above ground

You have probably heard about base jumpers leaping from heights of 500 feet, 300 feet, even sub 200 feet! While it is possible to successfully deploy a parachute at these crazy low heights, that isn’t the norm! Base jumpers use very specific parachute designs and systems, and for skydivers, there are strict minimum heights. Safety is paramount!

The United States Parachute Association (USPA) lays out very clear guidelines on the minimum heights a parachute should be deployed. The minimum height recommended for you is based on your experience and expertise:

Novices and new students are required to deploy their parachutes by 4,000 feet above ground level.

Beginners (skydivers holding an ‘A’ license) must deploy their parachute by 3,500 feet above ground level.

Intermediate skydivers (holding a ‘B’ license) must deploy their parachutes by 3,000 feet.

Accomplished skydivers (holding ‘C’ or ‘D’ licenses) are recommended to deploy their parachutes by 2,500 feet. However, it is acceptable for more professional skydivers to drop to as low as 2,000 feet before deployment.

The absolute minimum height for safely deploying a parachute is considered to be 1,000 feet. This is strictly only recommended in emergencies, such as when being ejected from an aircraft; aircraft emergency parachutes are designed to open much faster.

Source https://www.explainthatstuff.com/how-parachutes-work.html

Source https://skydivingplanet.com/how-do-parachutes-slow-you-down/

Source https://skydivingplanet.com/how-do-parachutes-slow-you-down/

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