Parachutes
If something is dropped, gravity will make it fall faster and faster. If a person
jumps out of an airplane, they will start to fall very fast. While falling, a person will fall
at 118 miles per hour. To keep from hitting the ground so fast, the parachute was
invented.
How a Parachute Works
A parachute looks a lot like a large umbrella. It is used to slow down a person’s
fall – rather than going 118 miles per hour, a person may go 15 miles per hour. A
parachute is very simple. It uses air resistance. Air resistance
is a force that helps slow things down. If you have held your
hand out of a car window while the car was moving, you have
felt air resistance. Something large and flat gives more air
resistance but something thin and sharp, like a knife or a
needle, gives very little air resistance. Think about it – if you
drop a sheet of paper and a pencil at the same time, which one
will hit the ground first?
The Parachute Designers
Leonardo da Vinci (1452-1519), a great artist,
designed the first parachute. He drew a parachute shaped
like a pyramid with four strings holding a man. Although
Leonardo designed the first parachute, the first parachute
wasn’t built until two hundred and fifty years later.
Inventors finally made a parachute in 1777. That year,
Joseph Montgolfier dropped a sheep attached to a parachute.
Later, in 1785, J.P. Blanchard dropped a dog from a balloon.
Can you guess why they didn’t use their own parachute?
The First Parachute Jumps
The first person to use a parachute was L.S.
Lenormand – he jumped from a tower in 1783. With Lenormand’s jump and those that
followed, the parachutes were dropped. In other words, the parachutes were already open
and the man was just hanging there before they let go of the parachute. Later, in 1797,
the first high parachute jump was made. On October 22, 1797 André Jacques Garnerin
made the first high parachute jump above Paris, France. He rode a balloon up to 3,200
feet (975 m) and then he jumped from the basket.
He was definitely a daredevil.
Garnerin’s design had a problem – his parachute did not have a vent at the top to let the
air out, so he spun wildly as he fell. Luckily, he landed unhurt half a mile from the
balloon. Garnerin was the first man to design a parachute that could slow a man's fall
from a high altitude.
Parachute Design
The first parachutes were rigid. They didn’t fold into a bag. Instead, they had
ribs covered with material. The ribs were usually made of a lightweight wood. The first
non-rigid parachute that was used was made in the 1880s. The first parachutes were
always dropped from a balloon. They were always open before being dropped. In 1908,
an American, A. L. Stevens made a parachute that was carried in a pack.
For many years, parachutes were made of
silk. Nowadays, silk is no longer used. However,
nylon is used. Nylon is stronger and cheaper. A
parachute for a person is usually 24 to 28 feet
across. A parachute for cargo can be very large.
Sometimes the army will drop a tank or a jeep from
a plane and those are very heavy so the parachute
must be very large. Sometimes a cargo parachute
can be over 100 feet wide.
Modern Parachutes
Today, a parachute is kept in a pack –
similar to the way people wear a backpack. A
parachute is held on with a harness. A harness
holds the person safely to the canopy. Between the
harness and the canopy are suspension lines, or
ropes.
The canopy is the largest part of the
parachute – this is what provides the air resistance.
Comprehension Questions:
1.
Look up the word gravity in a dictionary – write the definition below.
______________________________________________________________
______________________________________________________________
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2.
Look up the word gravity in a bilingual dictionary – write the word gravity in
your own language. ____________________
3.
If a person jumps out of a plane, how fast will they fall? _________________
4.
Do not use a dictionary for this question – guess what the word invented
means. ________________________________________________________
______________________________________________________________
5.
What does a parachute look like? ___________________________________
6.
Can a parachute slow a person’s fall? ________________________________
7.
What does a parachute use to slow things down? _______________________
8.
Who designed the first parachute? ___________________________________
9.
The first parachute was designed in the 1400s. How many years later did
someone make the first parachute? __________________________________
10.
Draw a picture of the first time a parachute was used:
11.
Who was the first person to use a parachute? __________________________
12.
Who made the first high parachute jump? _____________________________
13.
How high up was he when he jumped from the hot air balloon?____________
_______________________________________________________________
14.
Did he have a problem? If so, what was the problem? ___________________
_______________________________________________________________
_______________________________________________________________
15.
The first parachutes were rigid. This means that they were _______________
______________________________________________________________.
16.
When was the first parachute made that was carried in a pack? ____________.
17.
Who invented the parachute that could be carried in a pack? ______________
______________________________________________________________.
18.
What are parachutes made of today? ________________________________.
19.
How wide is a parachute that is made to carry people? __________________.
20.
What is another way to call suspension lines? _________________________.
Make a Parachute
Build your own parachute using Leonardo da Vinci's design for the first ever parachute. It looks like a
pyramid! Here’s how.
1. Take a sheet of
fairly stiff paper 30
cm long and 16cm
wide.
Fold it in half.
2. Open it out and
draw a line 1cm
from the long edge
to the middle fold.
3. Cut off this section
and fold back the
remaining piece –
it’s a tab so that you
can glue your
parachute together.
4. Now fold it along
the diagonal - from
corner to corner.
5. Open it out like a
book and measure
15cm up from the
centre fold. The
diagram will show
you exactly where
to measure.
6. Now join up the
points then cut out
your shape.
7. Fold it into a
pyramid shape and
glue it into place.
8. Make a small hole
near each corner at
the base.
9. Now tie strings,
each the same
length, to each hole.
You’ve made the Leonardo Da Vinci parachute!
Test it by attaching a weight (a piece of egg
carton makes a good basket for the weight) to
the strings and throwing it up into the air.
Experiment with different types of material.
Does newspaper or card or plastic carrier bag
work better?
How can you measure this?
Write up a report of your investigation of
different materials.
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Can you imagine you are Leonardo da
Vinci?
Find an illustration which shows you
how he might have worked.
Can you write out his thoughts as he
designed his parachute?
What did he know at that time?
What materials were available for
making his parachute?
What tools could he use?
Did he have scissors?
Can you illustrate your writing and make
it look “old”?
Science Projects with Toy Parachutes
By Dr. Jean Potvin
Parks College Parachute Research Group
There are many interesting scientific experiments that can be done to study the physics of parachutes.
These experiments involve dropping test parachutes of different designs in order to see their effects on the
payload's descent speed. Such design modifications include:
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changing the payload weight
lengthening or shortening the length of the suspension lines
changing the number of suspension lines
increasing or decreasing the radius of the parachute
cutting holes and/or slits in the parachute fabric
Some theory:
By virtue of being blunt and large, parachutes generate a lot of air resistance or "drag".
When attached to a freefalling payload, the large drag generated by a parachute helps in
reducing the payload's fall speed by acting against the payload's weight. In general,
parachute drag will increase with the radius of the chute and thus reduce the payload's
speed. Also, drag will be reduced when holes or slits are cut in the canopy fabric, i.e., the
more holes, the faster the descent. Finally, adding suspension lines will reduce the
effective parachute surface area; in contrast, lengthening them will increase it somewhat.
In terms of fall speeds, this means that adding suspension lines will increase the descent
rate while lengthening them will decrease descent rate.
The descent speed of a payload attached to a parachute is calculated by a well-known formula discussed in
another page on this web site, Calculating the Descent of a Round Parachute.
How to make small parachutes for science projects:
Toy parachutes can be purchased or made by using simple materials such as strings,
plastic from garbage bags or nylon fabric from old (discarded!) tents. These pictures
show some of the designs we have tested, a parachute without holes and a parachute with
holes.
Other sources of small parachutes:
Hobby stores that sell model rockets usually sell small rocket recovery parachutes, made
from both plastic for small rockets, and from fabric for the larger rockets. A parachute
supply company called Para-Gear also sells a small parachute. Item: A3333,
Name:Parachute Toy. Note: Before simply purchasing a parachute, make sure your
research or science project allows you to do so! An important part of your project might
be to make your own, which is easy, fun, and inexpensive anyway.
How to measure descent rates:
A typical experiment would consist in dropping different parachute designs and measure
the descent speed of each design. The easiest way to measure descent speed is by
suspending under the payload a long weighted line called a "plumb line", and by
measuring the time between the landing of the plumb line weight and the landing of the
payload. The length of the plumb line should be measured before or after the drops. The
descent speed is simply given by dividing the plumb line length be the landing time
interval of the payload and plumb line weight. An important note: the weight at the end
of the plumb line should be small relative to that of the payload so to not change the
desired descent speed of a given design. The weight is used to keep the plumb line
straight during the descent.
Some final remarks:
* In general, chutes that do not have holes and slits cut in the fabric tend to oscillate
wildly during their descent. This is due to the fact that the excess air caught by the
descending canopy spills to one side when there is too much of it in the canopy. This
sideways spill in turns pushes the canopy in the opposite direction to one side of the
payload, thus generating the oscillation when the spill is repeated. One way to reduce the
oscillations is to cut holes and slits that let some trapped air through. There are all sorts of
hole and slit patterns that can be cut as shown in an article by Dr. C. W. Peterson that was
published in Physics Today, August 1993 (the magazine Physics Today can be found at
university and college libraries).
* Tests chutes may be covering some horizontal distance while descending. This may be due to the
presence of winds, and/or to the parachute being unevenly trimmed. Uneven trim arises whenever the
suspension lines are not of the same length or when the holes/slits are not of the same size or located
symmetrically with respect to the parachute's center.
In the event that the chutes go forward, a proper measurement of the descent rate should involve the extra
measurement of the horizontal distance covered. This is easily done by measuring the horizontal distance
between the drop point and the landing point of the payload.
Then the descent speed is given by:
v =
travel distance
-----------------------landing time interval
where
(travel distance)^2
length)^2
= (horizontal distance)^2
+
(plumb line