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. 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 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 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
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 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, 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 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 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 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, 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 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 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 at night,