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Diagram of launch tube and lift charge

Launching Tube

Most fireworks are launched from rows of steel tubes which are secured in troughs of sand. The tubes or "mortars" are three times as long as the firework shells, but are the same size in diameter. If a firework doesn't fit snugly in its launching tube the pressure created from the lift charge will escape, and the firework won't become airborne.

Lift Charge

When gunpowder burns in the open air, the heat and gas it generates quickly dissipates. But if the gunpowder is confined, say in a pouch at the bottom of a firework cylinder, the heat and gas are trapped and will push wildly at the inside of the launch tube until an explosion results. This explosion will free the heat and gas, and hurtle the firework shell as high as 1000 feet into the air.

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