Almost as wildly anticipated as having a long weekend are the Fourth of July fireworks. We see them at every big holiday and event, yet we know next to nothing about them. So our inner pyro geek came out to investigate...
Aerial shells. Image from HowStuffWorks.com.
The large fireworks put on by your local government (or large retailer in NY) come in neat little packages called aerial shells. Aerial shells, pictured above, work a little like firecrackers and sparklers. The bottom cylinder part contains a lift charge of black powder (used in firecrackers) connected to the green string fuse. The spherical part contains a separate time fuse inside, a burst charge of black powder in the middle, and "stars" which are essentially the visible part of the fireworks. The stars, a bit like sparklers, are sometimes composed of aluminum, iron, steel, zinc, or magnesium to create the bright sparks.
The shells are placed in mortars, usually in the ground for safety reasons. When the fuse is lit, the lift charge is ignited, which in turn ignites the time fuse and shoots the spherical shell into the sky. Once the shell reaches the correct altitude, at the moment when it hangs in the air, the time fuse ignites the burst charge, creating a giant explosion. The shell explosion causes the stars to burn and give off sparks, and these create the fireworks that we see.
A diagram of how aerial shells vs. cylindrical shells work.
Image from Pyro Spectaculars, the team behind Macy's 4th of July and other national and international fireworks displays.
Different shapes, configurations, and colors in the fireworks are the result of various chemical composition and placements of the stars, and the placement of the time fuse. Cylindrical shells, pictured in the above diagram, have 2 sets of stars and the time fuse of the top set is ignited first before the lift charge. This lets the top set explode first, with the second set following immediately after.
Image taken from Pyro Spectaculars.
Imagine a thousand of varied shells and that is what we'll be seeing this Sunday.
Information gathered from How Stuff Works, Pyro Universe, and Pyro Spectaculars.
/////// V S
Tweet
0 comments:
Post a Comment