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To make an airship work, you need a few basic things: First, you must use a lighter-than-air gas like helium to lift the airship off the ground. Because helium weighs less than air, it floats up; a rock, which is heavier than air, drops. Then you need something to hold the helium so that it won't float away. Something light, such as a balloon, is best. The large airships of the past used many giant airtight bags inside the rigid frame and then covered the outside with canvas.

So you won't float too high, you need weights on the airship. The weights are called ballast. Water is used most often. When you want to rise from the ground, you drain some water out. When you want to come back to the ground, you release some helium.

To steer to the left or right, you need flaps called rudders. To steer up and down, you use flaps called elevators. Some blimps have engines that can rotate in different directions to help steer.

To move forward, you need a motor with propellers.

In a blimp, the cockpit is inside a gondola, which is like a small room at the bottom of the blimp. This is where the pilot sits and controls the blimp.