Sunday, September 28, 2008

Aerial Fireworks

An aerial firework is normally formed as a shell that consists of four parts:
Container - Usually pasted paper and string formed into a cylinder
Stars - Spheres, cubes or cylinders of a sparkler-like composition
Bursting charge - Firecracker-like charge at the center of the shell
Fuse - Provides a time delay so the shell explodes at the right altitude
Located just below the shell is a small cylinder that contains the lifting charge.

These are small shells, about the size of a peach, that you can buy at roadside stands in some states. The sphere is the shell, and the small cylinder below is the lifting charge that shoots it out of the launch tube. The green fuse lights the lifting charge, which in turn lights the shell's fuse. Shells that you see at a show are typically the size of a cantaloupe or even larger.

The shell is launched from a mortar. The mortar might be a short, steel pipe with a lifting charge of black powder that explodes in the pipe to launch the shell. When the lifting charge fires to launch the shell, it lights the shell's fuse. The shell's fuse burns while the shell rises to its correct altitude, and then ignites the bursting charge so it explodes.

Simple shells consist of a paper tube filled with stars and black powder. Stars come in all shapes and sizes, but you can imagine a simple star as something like sparkler compound formed into a ball the size of a pea or a dime. The stars are poured into the tube and then surrounded by black powder. When the fuse burns into the shell, it ignites the bursting charge, causing the shell to explode. The explosion ignites the outside of the stars, which begin to burn with bright showers of sparks. Since the explosion throws the stars in all directions, you get the huge sphere of sparkling light that is so familiar at fireworks displays.
Multibreak ShellsMore complicated shells burst in two or three phases. Shells like this are called multibreak shells. They may contain stars of different colors and compositions to create softer or brighter light, more or less sparks, etc. Some shells contain explosives designed to crackle in the sky, or whistles that explode outward with the stars.
Multibreak shells may consist of a shell filled with other shells, or they may have multiple sections without using additional shells. The sections of a multibreak shell are ignited by different fuses. The bursting of one section ignites the next. The shells must be assembled in such a way that each section explodes in sequence to produce a distinct separate effect. The explosives that break the sections apart are called break charges.
Next, we'll look at how fireworks explode in various patterns during a display.

Thursday, September 25, 2008

Footprint Fireworks Were Faked into Olympics Opening TV Show

A local Beijing paper has revealed that some of the amazing fireworks in the Olympics opening show were digitally-crafted fakes, inserted into the live TV feed. The Beijing Times quotes the head of visual effects, who says that the 28 giant footprints that stomped through the air above the city, ending at the stadium, were advanced CGI. Though the pyrotechnics really were set off, the airborne camera view that the rest of the world watched was fake. Why go to these lengths? Apparently the Olympic committee decided that to follow the real trail of firework footprints was too dangerous for a helicopter camera. Instead a team spent almost a year crafting the fake segment, paying attention to even get the smog lighting effects correct.

China bans fireworks in clubs after deadly fire

Tue Sep 23, 2008 3:31pm BST
BEIJING (Reuters) - China banned on Tuesday fireworks displays in public entertainment venues, just days after 43 young revellers were killed in a fire at an illegal dance hall.

The fire in Shenzhen, just across the border from Hong Kong, broke out just before midnight last Saturday at the packed King of the Dancers club, sparked by a fireworks display.

"Any type of fireworks is banned in public entertainment places," State Council's Work Safety Committee said in an announcement, pointing to Saturday's fire as an example.

The announcement also required local governments to improve the safety of such venues and to shut down those that do not meet the stricter standards.

(Reporting by Yu Le; Editing by Kirby Chien and Valerie Lee.)