Parachute Shape and Falling Speed
Date: December 2007
How does the shape of a parachute affect its falling
speed, when all the shapes have a relatively similar surface area?
The basic principle of a standard parachute is drag. Drag is the
amount of force required to keep an object moving through the air
at a given speed, and it increases with speed. The design of a
standard parachute (for someone jumping from a plane we will say)
is to have enough surface area that the amount of drag equals their
weight at a relatively slow and safe speed.
Now for the less than standard part. You may have seen some pictures
with parachutes that were pulled into a much longer, narrower shape.
This is done by restricting how far the same parachute can open. This
way, the rate at which the jumper slows down is not so great right at
the start of their jump. Consider that a human body can fall at around
120 MPH, and a 'safe' landing speed might be closer to 5 MPH. At 120
MPH, the force of drag on that parachute would be so great, it would
likely injure the skydiver, or just break the lines it is attached with.
Now for even LESS standard parachutes. The large, square parachutes
you have probably seen do not rely solely on drag to slow their user
down. They are cut and trimmed so they form an airfoil as they
descend. This airfoil acts like a wing, and even begins producing
lift! The trade off for the reduced drop rate though is an increased
forward momentum the skydiver will have to deal with once they touch
down. (instead of coming straight down, they are now moving forward
at the speed of a good run!) Usually, this can be turned to the
skydiver's advantage though, to counter wind, or aim for a specific
spot on the ground.
That is an excellent question, especially since the sport parachute has
undergone so much development in the past 30 years that I have been
Today's chutes, called wings, are just that. They are shaped so that
they fly forward and develop lift just like an airplane wing. As such,
they are very maneuverable and land far easier than the old round ones.
They are, however, a little more likely to malfunction. If a modern
chute stops moving forward with respect to the wind, it "stalls" and
falls pretty much straight down rather quickly. The lift you get
depends upon the surface area of the chute, its design and your weight.
On the whole, they stay in the air longer than the old designs.
The older chutes, called conical or spherical or just round, depended on
their design to catch air to slow descent. To provide some little
forward motion and control, panels of cloth were left out of the backs
of the chute. Air spilled out of the gores and forced the chute
forward. The mushroom shape of the canopy gave some lift, but not much.
These canopies are great for going pretty much straight down and they
deliver you to the ground with a pretty good thump (up to 20 mph)
depending upon your weight and canopy size. Again, the rate of descent
was controlled by the size of the canopy. They maneuver like a wounded
elephant with a broken leg - that is rather poorly. It was impossible
to "fly back up" in one of these as you can with a wing if conditions
Go to a local drop zone for more information. Believe me, like all
folks who have hobbies, parachutists will love to talk with you and give
you all sorts of ideas, prejudices and stories.
The shape of the parachute affects the parachute's drag. If the shape of
the parachute is aerodynamic (spherical or tear drop shaped), the drag will
be reduced, making the parachute ineffective.
Scott P. Smith
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Update: June 2012