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Fireworks Grow Up!

Science World, March 6, 2000 by Nicole Dyer

New technology lights up the millennium

One million people watched 20 tons of fireworks blaze over Harbour Bridge in Sydney, Australia

It may be one of the defining moments of the new millennium. As the 20th century drew to a close, millions watched as TV cameras around the world zoomed in at midnight, January 1, 2000. The planet was united in celebration as a sea of humanity witnessed the launch of a new century--and the most awesome fireworks shows in history.

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Twenty-four minutes of dazzling explosions glittered 1,000 meters (3,281 feet) above the Sydney Opera House in Australia. In Paris, fiery streams of red and blue transformed-the Eiffel Tower into a rocket ship ready for blastoff. And in Washington D.C., the 168-meter-high Washington Monument blazed with a cascade of electric white stars like a giant diamond water-fall. What was behind these showstoppers? Famous fireworks designers like the Grucci family (who created the Washington Monument spectacle), basic science, and new technology!

How FIREWORKS WORK

At the core of pyrotechnics (the science and art of fireworks) lies basic chemistry. Working in a lab, pyrotechnicians (fireworks experts) carefully pack papier-mache shells with powdered chemical compounds, molecules combining atoms of two or more elements. The compounds determine the color of a firework when it explodes. For example, shells stuffed with an aluminum mixture (containing barium, an element that stabilizes fireworks) produce brilliant white sparks. Compounds with the element strontium emit fluorescent red dazzlers, while lithium compounds create purple fireworks.

Shells launched into the sky are called aerials. But not all shells soar upwards. Some are mounted onto grids on the ground to form words or numbers like 2000. These shells, called set pieces, explode in place, lighting up the grid. When a shell is lit, chemicals inside react with each other--bonds between chemical atoms break and rearrange to form new chemicals. This exothermic, or energy-releasing, reaction releases energy in three forms: heat, light, and sound--key ingredients in any fireworks blowout.

ENTER COMPUTERS!

There's more to fireworks than chemical collisions. "Computers have revolutionized the way we design firework shows," says expert Philip Butler of Fireworks by Grucci. Computer programs help coordinate the synchronized firing of thousands of fireworks from just one or two stations called firing panels. also help trigger explosions faster and with more precision.

When President Clinton pushed the button on the firing panel for the Washington Monument fireworks, he launched a computer-generated display dreamed up by the Gruccis. To the eye it looked like a fireball on water. A two-story-high wall of electric white sparks raced over the 610-meter (2,001-ft)-long reflecting pool toward the monument base.

What's the pyrotechnic trick? First, the button sets off a moving electrical charge, or current. The current sends an electrical signal to a computer inside the firing panel that sends ignition cues to the fireworks. (For the fireball stunt, pyrotechnicians rigged fuses to tiny rockets set up every six meters.) A computer-generated electric signal races along a wire until it smashes into a metal match head, a small ball resembling a real match head. When the current hits a match head, the head ignites a spark. The spark lights a fuse, and the burning fuse lights the rocket. The resulting heat causes chemical gases inside the rocket to expand, creating pressure inside the rocket. This pressure forces gases to burst through a small hole at the top of the rocket, projecting giant sparks 12 meters into the air.

In less than a millisecond, the computer transmits another electrical signal to the next fuse. KABOOM again! A second burst of sparks shoots into the air. The computer continues to send firing signals to the rockets, igniting them one after another. Like falling dominoes, it appears as if the ball of sparks is speeding down a line.

A stunt like this would be impossible without computers, says Butler. "Only a computer is fast enough to send a firing signal every millisecond." In fact, computers are so fast and precise they allow technicians to match individual firework explosions to notes in a song!

AIR SHOW

Aerial fireworks work differently than ground pieces. An electric signal ignites two fuses attached to a shell--a quick-match fuse and a time-delay fuse connected to a lift charge--before it ever leaves the ground (see diagrams, p. 17). The quick-match fuse and lift charge send a jet of fire to black powder (similar to gunpowder) buried inside the shell. As the black powder bums, it emits the energy necessary to hurl the firework into the sky.

As the shell soars into the air, the burning time-delay fuse ignites chemical-packed pellets called stars, which are buried inside the shell. The heat transmitted by the time-delay fuse causes chemical bonds in the stars to shatter, releasing energy. The exothermic reaction transforms the mixture of chemical powders into hot gases that expand rapidly. Suddenly, the star blows the shell open, creating a dazzling show.

Fireworks Grow Up!

Science World, March 6, 2000 by Nicole Dyer

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