How computer geeks changed fireworks

by techtiptom

Originally posted on on 07/04/2010:

Devin Powell of Inside Science News Service (sponsored by the American Institute of Physics) has a pretty neat story about how computers have changed fireworks displays, enabling synchronization and sophistication that simply wasn’t possible not so long agos. Here’s the story:

WASHINGTON (ISNS) — This weekend, Tchaikovsky’s 1812 Overture will be played a thousand times across the country, accompanied by the bangs and booms of fireworks shows that have become more precisely choreographed than a Broadway musical.

Convincing a dozen fireworks to burst at exactly the same moment and in time with a cymbal crash requires split-second timing that wasn’t possible 25 year ago, when fireworks displays were lit by hand with road flares. Today, technological advances — including disposable computer chips implanted in the fireworks themselves — allow pyrotechnicians to fine tune their shows down to a thousandth of a second.

These pyrotechnicians are, in a sense, amateur neuroscientists who exploit the limits of the human eye. Lab experiments have shown that if two bright flashes are separated by less than a tenth of a second, our brains think that they happened at the same time. That’s why we don’t notice the flicker in our television screens, which display 30 or 60 images per second.

A synchronized pair of fireworks must explode less than a tenth of second apart. Every additional firework included raises the difficult level of beating this visual limit.

“At our high end shows, you should feel and see the fireworks and the music all as one emotion,” said Doug Taylor, President of Zambelli Fireworks Internationale in New Castle, Penn. “You can’t get that unless you’re exacting.”

To achieve this precision, fireworks show designers script their displays weeks ahead of time using a computer program. As the sound waves of the music roll by on the computer screen, they choose shells that translate the musical elements into the colors and shapes — the “rocket’s red glare” moment in “The Star-Spangled Banner” is a perfect spot for a Red Comet rocket, which leaves a trail of color in the sky.

The computer program consults a database to figure out how many seconds ahead of time each shell should be launched to explode at the right musical moment — heavier shells tend to fly slower than lighter shells — and saves the script as a “time code”.

Once the show starts, the humans step back, and the computer becomes the conductor for the night. A typical municipal Independence Day show costs up to $100,000 and consumes 15-20,000 fireworks, often launched from a dozen different locations. The central computer broadcasts the time code to all of the firing systems, which ignite each firework at the proper time using an electric match — a small bit of wire that heats up and ignites a lump of flammable material.

FireOne, one of the most commonly-used systems, can launch dozens of fireworks within a hundredth of a second of each other.

But even with such improvements in launching precision, the timing of a firework’s explosion also depends on the quality of its design and manufacture.

About 95 percent of all fireworks are made by hand in China. The basic design hasn’t changed much over the past 100 years — a round ball lifted is packed with black powder and chemicals that glow brightly when ignited. A timing fuse, lit when the firework is first lifted into the sky by smaller wad of powder, determines how long it will fly before bursting.

This timing fuse isn’t always exact. To achieve the most difficult effects, some companies have replaced it with a tiny computer chip clock. This clock starts ticking when the pyrotechnic is launched and dies a spectacular death when it sets off an electric match inside the firework, triggering the explosion at exactly the right moment.

These chips are accurate down to a thousandth of a second, less time than it takes the human eye to blink. This precision comes at a cost, however. Including a chip raises the price of a firework by 40 percent.

“On New Year’s Eve, we can put digits into the sky that replicate the numbers ten, nine, eight, etc.,” said Felix Grucci, Jr. of Fireworks by Grucci in Brookhaven, N.Y. “We launch hundreds of shells into the sky and, depending on the programming of the chips, they burst at the same time to form the digit.”

Grucci used these chips to create a fireworks rainbow over New York City’s East River in 2008 and to coordinate 10,000 fireworks launched within seconds of each other to form a swirling tornado of sparks over the skies of Washington in 2005.