12 Ways That The Technology Of Fireworks Might Surprise You

Here are a dozen things you might not have known about the science and engineering that goes into fireworks.
  • INTRODUCTION

    For a product that was first developed in the 6th Century AD, it’s surprising how much technology and innovation still goes into a modern fireworks display. The combination of chemistry, physics, electronics, and even computer simulations that are applied to aerial explosions and starbursts is impressive. So this Independence Day, as you and your family ooh and ah over the display, give a moment’s thought to the engineers and technicians who make it all possible.

    Here are some interesting fireworks facts to help you understand the science behind the boom.

    Senior Editor Kevin Clemens has been writing about energy, automotive, and transportation topics for more than 30 years. He has masters degrees in Materials Engineering and Environmental Education and a doctorate degree in Mechanical Engineering, specializing in aerodynamics. He has set several world land speed records on electric motorcycles that he built in his workshop.

    (Image source: US Department of Defense)

  • EARLY HISTORY

    The general agreement is that fireworks were invented in China, probably sometime in the second century B.C. in ancient Liuyang. The first natural "firecrackers" were bamboo stalks that would explode with a bang when thrown into a fire because of overheating of the hollow air pockets in the bamboo stalk.

    Later, during 600-900 AD, a Chinese alchemist mixed potassium nitrate, sulfur, and charcoal to produce the first “gunpowder.” When this powder was poured into hollowed out bamboo sticks and ignited, the result was fireworks and eventually early rockets.

    The concept made its way to Europe in the 13th century, and by the 15th century Fireworks were widely used for religious festivals and public entertainment. The Italians were the first Europeans to manufacture fireworks, which became a popular way for royalty to celebrate special occasions.   

    (Image source: American Pyrotechnics Association)

  • JULY 4th

    The US Independence Day on July 4th has been a federal holiday since 1941. Independence Day celebrations, however, go back to the 18th century and have their origin with the American Revolution. On July 2nd, 1776, the Continental Congress voted in favor of independence, and two days later delegates from the 13 colonies adopted the Declaration of Independence, which had been drafted by Thomas Jefferson. From 1776 until today, July 4th is celebrated as the birth of American independence, and the most spectacular part of those celebrations have been the fireworks displays.

    (Image source: Jean Leon Gerome Ferris/American Museum)

  • LAUNCHING INTO THE SKY

    The commercial fireworks shell is launched from a short steel pipe called a mortar. A lifting charge of black powder explodes in the pipe and pushes the shell outward at great speed. The lifting charge also usually lights the shell fuse, which burns while the shell is rising to the correct altitude for the bursting charge to blow the shell apart. The launch speed of a firework can be as high as 150 mph and the altitude can be as high as 1,000 feet above the ground. The largest shells can be two to three feet in diameter.

    Rockets can also be used to launch shells into the sky. The simplest version is probably the bottle rocket, where igniting the fuse causes the propellant to burn, pushing hot gasses out of the nozzle and propelling the rocket forward (see Newton’s Third Law of Motion). Simple bottle rockets can travel as high as 50-75 feet into the air. Sometimes larger rockets are used to launch commercial shells, however the cost can be significantly higher than the mortar system that is in more general use.

    (Image source: Skylighter)

  • COLORS AND WHERE THEY COME FROM

    The bright colors that occur during a fireworks display are the result of the combustion of metal salts. Commonly used are strontium carbonate (red), calcium chloride ( orange), sodium nitrate (yellow), barium chloride (green) and copper chloride (blue). The materials have to be chosen carefully avoiding ones like sodium chloride (table salt) that absorb water and would produce a fizzle rather than a sizzle. We may like the brightest reds and yellows, but firework designers say it is actually pure white and dark blues that give them the most trouble.

    (Image source: sciencenotes.org)

  • DANGEROUS REDS

    The brilliant red color that is a favorite among fireworks aficionados has a dark side. The red hue comes primarily from strontium monochloride, which comes from burning strontium compounds with polyvinyl chloride and a range of other pyrotechnic compounds. But the combustion of this mixture also produces a variety of polychlorinated aromatic compounds, most of which are highly carcinogenic. The cancer causing chemicals fall back to earth after the oohs and ahs are over.

    Looking for an environmentally-friendly to produce the red, researchers have found that replacing the polyvinyl chloride compound with a citrus preservative (hexamine) or a material used in airbag propellants. This removes the cancer-causing chlorine and results in a relatively safe compound, strontium monohydroxide, that produces bright reds while avoiding the production of strontium oxide, which has a less-pleasing orange color.

    (Image source: Fireworks International)

  • PATTERNS OF LIGHT

    The commercial fireworks shell is a container, usually made of paper and formed into a cylinder. A simple shell that explodes into stars might be pieces of sparkler compound, each about the size of a peak. The stars are poured into the paper tube and then are surrounded by black powder of the bursting charge. A fuse is lit as the shell is launched and when it burns into the shell it ignites the black powder, causing the shell to explode. At the same time the sparkler compound is ignited and the sky is filled with a shower of brightly burning stars.

    More complicated shells can be made with different sections containing different colors and star effects that burst in two or three different phases. Different sections of the shell can be ignited at different times using separate fuses.

    To create a pattern, the outline of a figure can be done with star pellets that can then be blown apart with explosive charges to make the figure grow larger. Timing is obviously critical or the figure won’t grow properly.

    (Image source: American Pyrotechnic Association)

  • CONTROLLED BY PHYSICS

    Calculating the trajectory for a fireworks projectile, launched from a mortar tube is a straightforward two-dimension kinematics problem. In this case the initial launch velocity is positive, the acceleration due to gravity is negative, and the maximum altitude depend only upon the vertical component of the initial velocity (neglecting air resistance on the shell). The horizontal velocity (moving downrange) is a constant (neglecting air resistance) and the position depends upon the time of flight.

    (Image source: study.com)

  • SOFTWARE AND SIMULATIONS

    Building a professional fireworks show takes a lot of planning, much of which is done using computers and simulation programs. Choreography using a software tool from Finale Fireworks or one from ShowSim allows designers to preview their creations without the explosives ever leaving the ground. Interactive 3D perspectives also let the creative developers view the show from different audience viewpoints.

    Prior to the invention of “e-match” the pyrotechnics were fired by hand using manual switch panels. But now, once the show has been fully programmed, script files can be exported to the firing system to make sure that each launch and explosion is timed to perfection. Better and safer shows are the result.

    (Image source: ShowSim)

  • COSTS FOR FIREWORKS

    With more than 14,000 fireworks displays across the US every July 4th, commercial fireworks are big business. A large scale event that incorporates music and large-sized shells can cost about $2,000 per minute. Typical municipal shows range from $5,000 to $30,000 or more—sometimes much more. Some of the largest shows in New York City, Washington D.C. and Philadelphia set off more than a thousand shells and can cost in excess of $6 million. According to the American Pyrotechnics Association, 2016 revenue for display fireworks was $332 million in the US.

    The world’s largest fireworks display is said to be the 2012 golden jubilee anniversary of Kuwait’s constitution. The display lasted for more than an hour and is reported to cost over $15 million.

    (Image source: Jakes Fireworks)

  • INJURIES ARE RARE

    Setting off commercial fireworks is a job that is not to be taken lightly. Although injuries are fairly rare, they can include burns, eye and hand injuries, and even death. A larger risk comes from pieces of burning firework landing on a building or in a field and starting a fire.

    Injuries in the factories that make fireworks can be deadly. In 2017, seven people were killed in Pingxiang, Jiangxi province in China in a factory explosion.

    Consumer fireworks, the kind that seem to flood your neighborhood on the 4th of July and New Year’s Eve, are much more dangerous. In 2016 for example, there were 11,000 fireworks-related injuries between June 16 and July 18th. There were also four deaths related to fireworks in the US in 2016.

    Consumer fireworks are not legal in every state and are banned outright in Massachusetts. The American Pyrotechnic Association maintains a list of the rules for each state.

    Be careful and be smart—you don’t want to add to this year’s injury statistics!

    (Image source: Consumer Products Safety Commission)

  • ENVIRONMENTAL CONCERNS

    When fireworks are launched into the sky, they introduce a variety of chemicals into the atmosphere. Launching the shell requires an oxidizer, which is also needed for the shell explosion, and many fireworks contain oxidizers such as perchlorates. These can dissolve in water, contaminating rivers, lakes and drinking water. Fireworks displays are often done over bodies of water to lessen the chances of brush fires starting from any residual glowing embers. The result is pollution of rivers and lakes from unburned perchlorate residues.

    The smoke and particulate matter created by the launch of the shell can result in locally poor air quality for hours after the display is over. The colors in firework displays come from metallic compounds and salts (such as barium or aluminum) and many of these chemicals can also be harmful to both people and the environment.

    Work is underway, using recycled materials and alternatives to the perchlorate rocket fuel used to launch the shells. Some newer, ‘cleaner’ fireworks replace perchlorates with safer alternatives, or use compressed air to reduce smoke created.

    (Image source: Andy Brunning/Compound Interest)

  • MANUFACTURING THE BOOM

    There are 2,800 fireworks factories in China. It is one of China’s oldest industries, dating back more than 1,000 years. Recently, licensing of fireworks factories in China has become more stringent as worker safety has become an issue. There are 407 fireworks manufacturers in the US.

    (Image source: Red Moon Fireworks)

 

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