How do blimps work?

Tune in to this episode of BrainStuff to learn more about blimps, from how they work to why they're a popular medium for advertisin

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Episode Transcript

Speaker 1 (00:00):
Welcome to brain Stuff from how stuff works dot com
where smart Happens. Hi Marshall Brain with today's question, how
do blimps work? At any major sporting event? There is
one thing that you're sure to see if the weather
is decent. It's that gigantic skywhale known as a blimp.

(00:25):
Like a helicopter, a blimp can provide a hovering platform
in the sky that makes them great for aerial photography.
But unlike a helicopter, a blimp does its hovering at
a much lower fuel cost. Blimps can stand the air
for days if they need to, and don't forget the
blimp bonus, there's a huge surface for advertising displays. The

(00:48):
obvious first question is the size. How big is an
actual blimp? They are immense by normal human standards. According
to Goodyear, you need to imagine a six story the
office building almost two feet long to get a sense
of a blimp scale. Or to put it another way,
imagine three eighteen wheelers parked end to end that handles

(01:11):
the length, and then imagine stacking four rows of those
on top of each other. A blimp is about sixty
feet high, while a tractor trailer is about thirteen and
a half feet high. An uninflated blimp, including the fabric
of the blimp itself, the gondola, and the motors, weighs
about thirteen thousand pounds. A blimp is a giant balloon

(01:34):
made out of fabric. There is no internal frame or structure.
You might remember the famous film of the Hindenburg exploding
with its immense aluminum framework falling from the sky. A
blimp has none of that. It's a big balloon with
a gas inside giving it its shape. That gas is

(01:54):
the key to the blimps ability to float. Blimps are
filled with helium, and a lot of it. Think about
a normal helium balloon that a child gets at a
birthday party. The balloon holds half a cubic foot or
about fourteen leaders, and can lift about fourteen grams. Keep
in mind that there are four hundred and fifty three
grams in a pound. To get a blimp off the ground, therefore,

(02:18):
you need a whole bunch of helium. Just think about
a fifty pound child. It would take about sixteen hundred
birthday balloons to get the kid off the ground. To
get a thirteen thousand pound blimp off the ground, Therefore,
you need a whole lot more helium over two hundred
thousand cubic feet to be exact. That's why blimps are

(02:39):
so gigantic compared to an airplane that can carry the
same number of people. Of course, an airplane can't cover
in the air for days at a time either. The
pilot who operates the blimp plus any passengers right in
the gondola. Inside the gondola looks a lot like the
cabin of an eight seater airplane. There are two pilot
seats at the runt and six passenger seats behind. The

(03:02):
controls that the pilot uses look a lot like the
controls of an airplane as well. At the back of
the blimp there are big fins that act as the
rudder and elevator for steering the blimp, and a blimp
has two piston engines spinning normal airplane propellers to get
the blimp moving forward through the air. You might have
noticed that a birthday balloon, once set free, has this

(03:26):
tendency to rise until it's out of sight. Essentially, a
birthday balloon goes up until it bursts. What keeps a
blimp from doing that? For one thing, a blimp starts
its trip with enough ballast on board to be just
slightly heavier than air. If you could put a blimp
on a bathroom scale, it would weigh about a hundred
pounds at take off. That keeps it on the ground,

(03:48):
but just barely The slightest gust of wind could kick
it up into the air. Plus, the blimp gets lighter
as it burns fuel. Therefore, inside the blimp there are
two large balloons called balonetts. These fill with air under
the pilot's control. Since air is a lot heavier than

(04:09):
helium relatively speaking, the pilot puts a lot of air
into the balonets when it's time to descend. To ascend,
the pilot lets the air out of the ballonets, allowing
the helium inside to uncompressed and have its full lifting power. Essentially,
the pilot is using big tanks of air as additional

(04:30):
adjustable ballast. The other big thing with blimps is the advertising.
It's possible to paint ads on the blimps fabric, and
people do, but those signs are invisible at night. Therefore,
blimps also have a rays of bright l ed s
for night advertising. A blimp becomes a giant floating JumboTron

(04:51):
at night,