Why do skydivers use parachutes?

Oct 3, 2022

Skydivers need to use parachutes because those are the apparatuses that give human beings the ability to reduce their falling speed enough that they are able to land safely on the ground.

That’s the short version, so let’s look at the physics behind this answer from a scientific position.

Skydiving & Falling Apples

Sir Isaac Newton [1] , well-known for his penchant for apples [2] , is better remembered for his formulation of the three Laws of Motion, the basic principles of modern physics.

The first law of motion describes inertia :

An object at rest stays at rest and an object in motion stays in motion with constant speed and in the same direction unless acted upon by an unbalanced force. [3]

Inertia is like momentum. The first law basically implies: if a thing isn’t moving, it will not start moving by itself. If a thing is moving, it will not stop or change direction unless some external force acts upon it. [4] A skydiver falling through the air cannot stop or slow down without the intervention of another force, which in this case would be the air resistance caused by a parachute.

The second law of motion addresses the cause and effect portion of falling. It states:

Acceleration of an object is dependent on the forces acting upon the object and the object’s mass. [5]

Keep in mind that acceleration exists whenever speed is changing, up or down. So it does not just mean going faster, it also refers to slowing down. In the case of skydiving, the second law of motion (F=m*a) or, Force = mass x acceleration, refers to the mass of the jumper plus their gear, as well as the forces it takes to speed them up (gravity) as well as the force that slows their descent (drag). We’ll get deeper into that a bit further down. * See illustrations below.

The third law of motion refers to a kind of natural symmetry, or the action/reaction effect.

Whenever one body exerts a force on a second body, the first body experiences a force that is equal in magnitude and opposite in direction to the force that it exerts. [6]

When you stub your toe on the corner of a door, both objects involved (your toe and the door) experience a force. That force translates into movement for the door, and pain for the toe. This applies during skydiving as air resistance acts on our body surface, creating the slowing down effect, or drag that we just mentioned .

Why Skydivers ReachTerminal Velocity

While the skydiver is in the airplane getting ready to jump, she is traveling horizontally through the air in tandem with the airplane. At this moment, gravity is being neutralized by the lift force caused by the air passing through the plane’s wings. This is true until she steps out of the aircraft and begins to accelerate on the vertical axis.

As the skydiver accelerates she gains momentum, and the air she passes through creates a resistance that pushes back up at her, increasing drag.

Eventually, the force of the resisting air balances out with the force of gravity, and the skydiver stops speeding up. Once she has reached this balance and is no longer accelerating, she has reached terminal velocity. Which is to say: drag is equal to weight, acceleration is zero, so velocity is constant.

Terminal velocity is a weird term because it sounds scary, but is really quite the opposite. When you are no longer accelerating, you feel almost like you’re floating. On a skydive, everything that happens to your body is according to its natural physical motion. It is nothing like a roller coaster or bungee jumping, because you are not suspended or attached to an object that drags you out of you body natural acceleration range. Skydiving is a magical feeling!

What happens when the parachute is deployed?

When the skydiver reaches “pull altitude” (the height at which she needs to deploy the parachute), she pulls a mini parachute called pilot chute from a special pocket in her parachute container, flinging it into the wind. The wind catches the pilot chute and the drag it creates initiates the parachute opening sequence. Once out of the container, the main canopy is inflated by the wind, causing the amount of air resistance to increase even more, and neutralizing the force of gravity at a much lower velocity .

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Modern parachute canopy designs are made in a way that after inflated, the parachute becomes a wing. This creates lift as it glides thru the air, and also allows full controllability of the parachute’s heading direction as well as control over the glide, which is especially important for the landing.

So there you have it! Real facts for a valid question: why do skydivers use parachutes? You know, this article was almost much shorter. This was the first draft: “Because it saves their lives.”

How a parachute works and the design behind it

For the newcomer, skydiving equipment can seem a bit bewildering. How does a parachute work? Are there different kinds of parachutes? How could a big bunch of fabric possibly carry someone safely to the ground?

There’s no need to wonder any longer, as we unfold the mystery of the skydiving parachute right here.

Parachute History and Development

The parachute has a history that extends further back in time than you might think. A historical record written in 90 B.C. by historian Sima Chian describes a parachute legend predating present day by nearly 4,000 years. In this legend, the Emperor Shun utilized two large bamboo hats and the principles of air resistance to escape from the roof of a burning building.

This may have not been the ideal parachute equipment, but sometimes necessity is the mother of invention! Physical parachute designs were committed to paper as early as the 15th century by Leonardo da Vinci. Although, this design detailed a triangular shaped parachute very different from the parachute equipment that would eventually be utilized for successful parachute jumps. A few hundred years later, André-Jacques Garnerin constructed the first parachute that made effective use of air resistance and made the first parachute jump from 3,200 feet over Paris, on October 22, 1797. This general design of a “round parachute” to lower terminal velocity is still used today in military operations.

Military Rounds to RAM Air Squares

Skydiving gear varies based on its application. Parachutes used in military operations are round, dome-shaped canopies. Likewise, the surplus parachute equipment that was first used at civilian skydiving’s inception was also round.

Round parachutes offer consistent, docile openings; however, they lack any real steering ability. Thankfully for civilian skydivers, in the 1960’s kite-maker Domina Jalbert invented the rectangular, RAM-air parachute. This is the basic type of parachute we use today.

Parachute equipment is a rapidly developing field, one in which improvements are still consistently made today. Despite an eve-changing industry, a few primary factors of physics are utilized in parachuting equipment of all kinds.

How do parachutes work? Parachutes, both round and square, work because of a phenomenon in physics called air resistance.

Air Resistance

While air seems to lack substance, it is composed of tons of gas molecules. As objects move through air, they push these molecules aside. When you increase surface area, the molecules cannot move out of the way as quickly, and the more air resistance you create. This air resistance is what lowers your terminal velocity and, in turn, enables a skydiving parachute to allow you to approach the ground slowly and safely.

Furthermore, many parachutes are made from a lightweight nylon material that has been chemically treated to be less porous. This allows less air to pass through the fabric and further increases the air resistance it creates.

Terminal Velocity

Both round and RAM-air parachutes lower the terminal velocity of the object or person falling through the air. So what is terminal velocity? Terminal velocity is a point at which no acceleration can occur. For skydiving, this occurs when the force of gravity is countered by an equal amount of air resistance.

RAM-air parachutes do more than simply increase air resistance. Instead of simply creating drag, modern parachute equipment allows you to fly. Modern parachutes are composed of two layers of material which are sectioned into long-tubular cells that open on the front end of the parachute and sealed at the back.

Air is forced into the cells as the parachute moves forward, and it stiffens the parachute and gives it shape. This, in effect, turns the parachute into a wing. The air beneath the parachute moves more quickly than the air over it, and this generates lift!

Staged Parachute Opening

In order to limit the amount of shock on the body and prevent significant snatch-force, parachutes are opened by a staged sequence. First, a mini-parachute is extracted from an elastic pouch that is sewn to the bottom of the parachute container. When this mini-parachute is extracted it inflates. As it inflates, it creates enough drag to extract the main parachute from the parachute container. The main parachute does not inflate all at once, but rather, it inflates with each of the airfoils (the long-tubular cells from above). This creates a nice soft transition from a freefall at terminal velocity to a gentle ride under canopy.

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Tandem Parachute

Tandem skydiving equipment operates in a very similar way to licensed skydiver equipment. Though because it bears a bit more weight, there are a few differences. The mini-pilot chute that extracts the main parachute is much larger. Additionally, the parachute itself is much larger. Tandem parachutes come in a range of sizes but most range from 366 square feet to 400 square feet. Whereas, a solo jumper canopy ranges in size from 260 square feet to an incredibly teeny tiny 67 square feet!

Feeling parachute savvy? Come visit Skydive OC, and let us show you how parachutes work firsthand!

Quick Skydiving Guide: How do skydivers move and breathe in the air? How do they land?

Skydiving is one of the most addictive extreme sports that you can do these days. As the saying goes, “If riding an airplane is flying, then riding a boat would be called swimming. If you want the true experience, get out of the vehicle.”

And it’s 100% true. Skydiving can even be therapeutic as it stimulates much-needed energy and positivity. One thing that makes skydiving so addictive is the idea of literally flying in the sky – that moment when there’s no difference between you and the birds.

That brings up a lot of questions though. How do you even navigate the skies, and more importantly, how do you land without any repercussions? When I first got into skydiving, I used to worry about all this too, but thankfully that didn’t stop me. I’ve been skydiving for 6+ years now and will answer all of your questions (and more) in this quick guide.

1. Do skydivers reach terminal velocity?

Skydivers reach terminal velocity about 10 to 12 seconds after jumping from the airplane. At that point, you reach maximum speed or the point of zero acceleration and begin to float in the sky as you descend to the ground.

Before I explain the steps, here’s what you need to know:

• Terminal velocity is the maximum velocity of the body when flowing through any fluid. If you didn’t know already, anything that “flows” is a fluid, i.e., air is also a fluid.
• Freefall is when you fall from the sky against only the force of gravity itself.
• Acceleration is the difference in speed. If your current speed is more than your actual speed, you’ve accelerated.

When you jump out of an airplane, you start falling because of Earth’s gravitational forces, right? Any object near Earth’s surface will accelerate at a constant rate of 9.8 m/s 2 . So, when you jump, you fall at a speed of 21.9mph after 1 second, 43.8mph after 2 seconds and so on. On average, skydivers can reach a maximum velocity of 200mph during freefall.

The terminal velocity of an average skydiver falling is 118.6 mph. In other words, after a few seconds, you’ll fall at a constant speed of 118.6 mph with zero acceleration, and this is where the fun begins!

A. How do skydivers float?

Does that mean gravity doesn’t affect you after a few seconds? No. This is where Archimedes’ principle of buoyancy comes into play. In layman’s terms, the principle states that “when something is flowing through a fluid, it displaces the tiny molecules and will be met by some resistance from the fluid particles.”

In a skydiver’s case, this resistance is air resistance. After a few seconds, your body stops accelerating and reaches the terminal velocity. The air resistance at that point is equal to gravity acting upon your body, and the net force becomes zero, making your body float in the air.

Yes! That’s what makes skydiving so addictive. There’s no fun in constantly falling or getting hung on a parachute. It’s those few minutes that make it truly blissful.

B. Can you breathe mid-air? Do your ears hurt while flying?

Even at 14,000 feet above ground, oxygen is still in the air.

Skydivers can breathe mid-air just like they would on the ground – while both free-falling at 160mph and floating at 120mph!

First-timers sometimes find it hard to breathe because of the extreme experience itself and not the lack of oxygen. But if you just take a deep breath and calm down, you can breathe normally. For the ears, it depends.

In general, your ears won’t hurt while skydiving. You’ll feel the altitude change a bit as it climbs, but that’s hardly a cause for concern. But skydiving when you’re congested can be dangerous. Worst case, your eardrums could puncture because of the congestion and blockage.

It won’t lead to permanent hearing loss, but it’ll hurt pretty bad. So, if you’re congested, you’re better off sitting one out.

2. Why do skydivers spread their arms and legs?

Skydivers spread their arms and legs to get in the “floater” position. This increases the air resistance (buoyancy force) on your body and slows down the rate of descent so you float longer.

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You can fly (float) in the air and move around however you want by positioning your arms and legs. Even though it feels like something straight out of a comic book, there’s a scientific principle behind it.

If you look closely at the definition of Archimedes’ principle, it works based on how many fluid molecules are being affected, i.e., it depends on the surface area.

This means, when skydivers spread their arms and legs to get into a “floater” position, they increase air resistance by increasing the body’s surface area.

A. How do skydivers regulate height?

For those who have played GTA games and jumped out of airplanes using parachutes, you already know these two positions.

Skydivers regulate their height by using two body positions: floater and diver. In the floater position, you spread your arms and legs to slow down the fall, while in the diver’s position, you keep straight (like a missile) to fall faster.

Different positions have different outcomes. You can move a knee and turn a full 360 degrees. Here’s a video on wind tunnel acrobatics that’ll give you a good idea of the effect of different positions while floating:

B. How do parachutes work, and when to open them?

Now that we’ve floated around enough, it’s time to start preparing for landing.

Parachutes work by taking advantage of Archimedes’ principle. Its large surface area and circular design trap much more air than your body so a huge amount of air resistance is created to deaccelerate your fall.

BUT, there’s one problem. You cannot trap fluids, especially gases, as they’ll start moving in random positions to try and escape. This can cause the parachute to flip upside down, which is very dangerous for the diver.

Here’s an excellent diagram by BBC.co.uk explaining the process:

This is why parachutes have a huge holes in the front.. Since the holes are much smaller than the parachute, the amount of air that’s trapped is more than the amount leaking out.

So, you can still accelerate while making sure your parachute doesn’t flip. This also helps skydivers change their direction by changing the angle of air leaking out of the parachute.

Skydivers open their parachutes based on the altitude. They usually carry two altimeters (one at the wrist and one at the helmet) to measure their distance above the ground. In case of failure, reserve parachutes have AADs to automatically open the ‘chute after a certain altitude.

If you want to know more about parachutes and AADs, read my ultimate guide on reserve parachutes and how they’re different.

3. How do skydivers know where to land?

First-time skydivers, especially tandem skydivers, are often worried about the landing and whether it’ll be dangerous. But in reality, modern landings are quite safe because of the flaring (the act of stopping the forward motion) of the parachute.

Nowadays, skydivers dive in pre-determined routes and landing destinations. You have to steer your parachute to a well-suited area and start flaring the parachute as you approach the ground for a successful and safe landing.

Skydivers generally land in one of two ways: feet-first or butt-first. Both are equally safe and can be used by tandem skydivers.

Here are some guidelines about choosing the right landing spot provided by The United States Parachute Association (USPA):

1. Always land under a flat and level parachute that’s not turning when you reach ground.
2. Steer your parachute to a clear and open, hazard-free area.
3. Use the parachute inputs to gradually bring it to a stop instead of hitting the ground hard.
4. Use the PLF maneuver to absorb any impact if things don’t go as planned.

That’s about everything you need to know about skydiving for the first time – from jumping off the plane to landing on the ground safely. I recommend trying skydiving at least once in your life. If you’re like me, you may even get hooked! If you have any questions, get in touch with me.

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I got into extreme sports about 20 years ago and am a die-hard adrenaline junkie. Just like in business, I choose my outdoor adventures based on how much they scare me. My goal is to share the lessons I’ve learned over the past couple of decades braving the unknown to encourage you to do the same.

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Elevated Adventurer is your go-to sherpa for all things adventure sports and outdoor exploration. Here you’ll learn everything you need to know about your favorite outdoor sports from rock climbing and scuba to skydiving and extreme sports.

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