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Speaker 1: Welcome to brain Stuff from how stuff works dot com

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Speaker 1: where smart Happens. Hi Marshall Brain with today's question, how

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Speaker 1: do blimps work? At any major sporting event? There is

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Speaker 1: one thing that you're sure to see if the weather

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Speaker 1: is decent. It's that gigantic skywhale known as a blimp.

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Speaker 1: Like a helicopter, a blimp can provide a hovering platform

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Speaker 1: in the sky that makes them great for aerial photography.

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Speaker 1: But unlike a helicopter, a blimp does its hovering at

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Speaker 1: a much lower fuel cost. Blimps can stand the air

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Speaker 1: for days if they need to, and don't forget the

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Speaker 1: blimp bonus, there's a huge surface for advertising displays. The

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Speaker 1: obvious first question is the size. How big is an

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Speaker 1: actual blimp? They are immense by normal human standards. According

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Speaker 1: to Goodyear, you need to imagine a six story the

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Speaker 1: office building almost two feet long to get a sense

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Speaker 1: of a blimp scale. Or to put it another way,

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Speaker 1: imagine three eighteen wheelers parked end to end that handles

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Speaker 1: the length, and then imagine stacking four rows of those

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Speaker 1: on top of each other. A blimp is about sixty

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Speaker 1: feet high, while a tractor trailer is about thirteen and

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Speaker 1: a half feet high. An uninflated blimp, including the fabric

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Speaker 1: of the blimp itself, the gondola, and the motors, weighs

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Speaker 1: about thirteen thousand pounds. A blimp is a giant balloon

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Speaker 1: made out of fabric. There is no internal frame or structure.

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Speaker 1: You might remember the famous film of the Hindenburg exploding

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Speaker 1: with its immense aluminum framework falling from the sky. A

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Speaker 1: blimp has none of that. It's a big balloon with

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Speaker 1: a gas inside giving it its shape. That gas is

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Speaker 1: the key to the blimps ability to float. Blimps are

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Speaker 1: filled with helium, and a lot of it. Think about

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Speaker 1: a normal helium balloon that a child gets at a

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Speaker 1: birthday party. The balloon holds half a cubic foot or

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Speaker 1: about fourteen leaders, and can lift about fourteen grams. Keep

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Speaker 1: in mind that there are four hundred and fifty three

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Speaker 1: grams in a pound. To get a blimp off the ground, therefore,

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Speaker 1: you need a whole bunch of helium. Just think about

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Speaker 1: a fifty pound child. It would take about sixteen hundred

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Speaker 1: birthday balloons to get the kid off the ground. To

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Speaker 1: get a thirteen thousand pound blimp off the ground, Therefore,

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Speaker 1: you need a whole lot more helium over two hundred

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Speaker 1: thousand cubic feet to be exact. That's why blimps are

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Speaker 1: so gigantic compared to an airplane that can carry the

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Speaker 1: same number of people. Of course, an airplane can't cover

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Speaker 1: in the air for days at a time either. The

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Speaker 1: pilot who operates the blimp plus any passengers right in

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Speaker 1: the gondola. Inside the gondola looks a lot like the

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Speaker 1: cabin of an eight seater airplane. There are two pilot

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Speaker 1: seats at the runt and six passenger seats behind. The

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Speaker 1: controls that the pilot uses look a lot like the

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Speaker 1: controls of an airplane as well. At the back of

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Speaker 1: the blimp there are big fins that act as the

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Speaker 1: rudder and elevator for steering the blimp, and a blimp

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Speaker 1: has two piston engines spinning normal airplane propellers to get

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Speaker 1: the blimp moving forward through the air. You might have

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Speaker 1: noticed that a birthday balloon, once set free, has this

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Speaker 1: tendency to rise until it's out of sight. Essentially, a

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Speaker 1: birthday balloon goes up until it bursts. What keeps a

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Speaker 1: blimp from doing that? For one thing, a blimp starts

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Speaker 1: its trip with enough ballast on board to be just

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Speaker 1: slightly heavier than air. If you could put a blimp

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Speaker 1: on a bathroom scale, it would weigh about a hundred

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Speaker 1: pounds at take off. That keeps it on the ground,

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Speaker 1: but just barely The slightest gust of wind could kick

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Speaker 1: it up into the air. Plus, the blimp gets lighter

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Speaker 1: as it burns fuel. Therefore, inside the blimp there are

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Speaker 1: two large balloons called balonetts. These fill with air under

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Speaker 1: the pilot's control. Since air is a lot heavier than

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Speaker 1: helium relatively speaking, the pilot puts a lot of air

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Speaker 1: into the balonets when it's time to descend. To ascend,

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Speaker 1: the pilot lets the air out of the ballonets, allowing

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Speaker 1: the helium inside to uncompressed and have its full lifting power. Essentially,

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Speaker 1: the pilot is using big tanks of air as additional

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Speaker 1: adjustable ballast. The other big thing with blimps is the advertising.

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Speaker 1: It's possible to paint ads on the blimps fabric, and

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Speaker 1: people do, but those signs are invisible at night. Therefore,

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Speaker 1: blimps also have a rays of bright l ed s

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Speaker 1: for night advertising. A blimp becomes a giant floating JumboTron

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Speaker 1: at night,