From Drones to Augmented Reality: Exciting New Tech Trends for July 4th
Traditional fireworks and new technologies light up the sky in the annual celebration of independence. Here, discover how fireworks are made and launched, how to calculate the trajectory of fireworks, and the new technology behind July 4th celebrations.
In 1776, the U.S. Continental Congress voted for independence, and two days later, on July 4, delegates from the 13 colonies signed the Declaration of Independence. A federal holiday since 1941, traditional Independence Day/4th of July celebrations date back to the 18th century.
Fireworks displays are the most spectacular part of these celebrations.
Traditional fireworks light up a 4th of July celebration. Image used courtesy of Jim.Henderson, CC BY 4.0 via Wikimedia Commons
The Invention of Fireworks: Bamboo and Gunpowder
The invention of fireworks is attributed to ancient China, likely dating back to the second century BC in Liuyang. The earliest firecrackers were bamboo stalks that exploded when thrown into a fire due to the overheating of hollow air pockets within them. During 600-900 AD, a Chinese alchemist discovered that a mixture of potassium nitrate, sulfur, and charcoal produced the first form of "gunpowder." This powder was poured into hollowed bamboo sticks and became an early precursor to rockets.
The concept of fireworks made its way to Europe in the 13th century, with Italy being the first to manufacture them. They became widely used for religious festivals and public entertainment by the 15th century and eventually became popular with royalty celebrating special occasions.
Fireworks. Image used courtesy of Pexels
How Are Fireworks Made?
Commercial fireworks shells are typically paper cylinders containing various sections. A simple shell that explodes into stars may consist of numerous sparkler compound pieces. These stars are poured into the paper tube and surrounded by a bursting charge of black powder. A fuse is ignited as the shell is launched, burning into the shell, and igniting the black powder, causing the shell to burst. Simultaneously, the sparkler compound ignites, filling the sky with a shower of brightly burning stars.
More intricate shells can be created with different sections containing various colors and star effects that burst in two or three distinct phases. Different shell sections can be ignited at various times using separate fuses. Patterns can be formed by outlining figures with star pellets, which are then blown apart by explosive charges to make the figure appear larger. Proper timing is crucial to ensure the figure grows correctly.
How Are Fireworks Launched?
Launching fireworks into the sky involves using a mortar, a short steel pipe from which commercial fireworks shells are propelled. A lifting charge of black powder explodes in the mortar, propelling the shell outward at high speed. The lifting charge also typically ignites the shell fuse, which burns as the shell ascends to the correct altitude for the bursting charge to explode. Fireworks can reach launch speeds of up to 150 mph and soar to heights as high as 1,000 feet above the ground. The largest shells can have diameters of two to three feet.
Fireworks. Image used courtesy of Pexels
Rockets are another means of launching fireworks shells into the sky. The simplest version is the bottle rocket, where igniting the fuse causes the propellant to burn, expelling hot gases through the nozzle and propelling the rocket forward (by Newton's Third Law of Motion). Basic bottle rockets can ascend as high as 50-75 feet. Larger rockets are sometimes used for commercial shells, although this method can be more costly than mortar systems, which are more commonly employed.
Calculating Fireworks’ Trajectory
The trajectory of a fireworks projectile launched from a mortar tube can be calculated using basic two-dimensional kinematics. Because the initial launch velocity is positive and the acceleration due to gravity is negative, the maximum altitude depends only on the vertical component of the initial speed (neglecting air resistance on the shell). How far the display moves downrange depends on the time of flight.
Planning a professional fireworks show involves significant preparation, much of which is done using computers and simulation programs. Choreography software tools like Finale Fireworks or ShowSim allow designers to preview their creations without needing actual explosives. Interactive 3D perspectives enable creative developers to visualize the show from various audience viewpoints.
Before the advent of "e-match," pyrotechnics were manually fired using switch panels. Now, however, script files can be exported to the firing system when after the show has been fully programmed, ensuring precise timing for each launch and explosion. This advancement leads to better and safer shows.
Colorful Sizzles, not Fizzles
The vibrant colors seen during fireworks displays result from the combustion of metal salts. Commonly used metal salts include strontium carbonate (red), calcium chloride (orange), sodium nitrate (yellow), barium chloride (green), and copper chloride (blue). The selection of materials requires careful consideration, avoiding substances like sodium chloride (table salt), which absorbs water and would result in fizzling rather than sizzling. While we may favor bright reds and yellows, firework designers find that pure white and dark blues often present more challenges.
The brilliant red color is a favorite among fireworks enthusiasts, but it has a dark side. It primarily comes from the combustion of strontium monochloride, produced by burning strontium compounds with polyvinyl chloride and other pyrotechnic compounds. However, this combustion also generates various polychlorinated aromatic compounds, many of which are highly carcinogenic. These cancer-causing chemicals descend to the ground and can pollute soils and waterways.
In the search for more environmentally friendly alternatives, researchers have found that substituting the polyvinyl chloride compound with a citrus preservative (hexamine) or an airbag propellant material can eliminate the production of chlorine, resulting in a relatively safe compound called strontium monohydroxide. This compound produces bright red hues while avoiding the less desirable orange color associated with strontium oxide.
Fireworks can also write messages in the sky. Different colors of fireworks and shades of light create letters and numbers. Special fireworks are designed to explode in specific patterns. These fireworks can be used to create more complex messages than can be created with traditional fireworks.
Fireworks Are Big Business
With more than 14,000 fireworks displays across the U.S. every July 4th, commercial fireworks have become a significant industry. Large-scale events incorporating music and large-sized shells can cost around $2,000 per minute. Municipal shows typically range from $5,000 to $30,000, sometimes even more. Major displays in cities like New York, Washington D.C., and Philadelphia can involve over a thousand shells and exceed $6 million in cost.
According to the American Pyrotechnics Association, the revenue from display fireworks reached $400 million in 2022.
The world's largest fireworks display reportedly consisted of 810,904 fireworks at the Countdown to 2016 New Year Celebrations in the Philippine Arena in Ciudad de Victoria Bocaue Bulacan. Despite a heavy rainstorm, the aerial display lasted over an hour and a half.
Fireworks manufacturing is a significant industry in China, with around 2,800 factories. In the U.S., there are 407 fireworks manufacturers. This ancient industry, dating back more than 1,000 years, has faced stricter regulations in recent years due to concerns about worker safety.
Safety (Human and Environmental) First
While professionally-produced fireworks shows have an excellent safety record, consumer fireworks, commonly seen during celebrations like July 4th and New Year's Eve, pose greater dangers. In 2021, there were 11,600 fireworks-related injuries in the U.S., including burns, eye and hand injuries, and even fatalities.
Consumer fireworks aren’t legal in every state, and the American Pyrotechnic Association maintains a list of regulations for each.
Fireworks displays also have environmental implications. The launch of fireworks introduces various chemicals into the atmosphere, including oxidizers like perchlorates, which can contaminate water sources when they dissolve. Fireworks can create smoke and particulate matter, leading to poor air quality for hours after the display. Additionally, the metallic compounds and salts used to produce the colors in fireworks can harm both people and the environment.
Technology is providing a safer alternative to traditional fireworks aerial displays. Electronics are often used to create festive light displays. In many cases, cities and towns will light up their buildings and landmarks in red, white, and blue, and electronic devices often power these lights. Electronic light displays can also create more elaborate displays, such as laser shows or choreographed light shows.
In addition to the traditional uses of electronics in July 4th celebrations, there are several new and innovative ways that electronics commemorate the holiday. For example, some cities use drones to create light shows, while others use augmented reality to allow people to interact with virtual fireworks displays.
Drones provide an interesting alternative to traditional fireworks. Image used courtesy of Masahiko OHKUBO, CC BY 2.0, via Wikimedia Commons
Drone light shows are typically created using a fleet of drones equipped with LED lights. The drones are programmed to fly in formation and create specific patterns or images. The designs can be simple, such as a heart or a star, or more complex, such as a patriotic flag or a corporate logo. Drones can create messages in the sky by flying in formation and carrying lights, a newer technique that is becoming increasingly popular.
Lasers can also provide impressive light shows without the environmental hazards of exploding fireworks.
When the COVID pandemic was in full swing, many public gatherings for fireworks displays were canceled. Some towns used augmented reality (AR) fireworks to replace the traditional flash and bang of July 4th celebrations.
Augmented reality fireworks aren’t physical fireworks. They are images projected onto a digital device. AR fireworks can be used to create a variety of effects, like making it appear as if fireworks are exploding in the sky overhead or shooting out of your hands.
Many different AR fireworks apps are available, some of which are free to try. These apps typically work by using your device's camera to track your movements and then projecting the fireworks onto your screen in the correct location. Some apps also allow you to customize the fireworks display by choosing the type of fireworks, the colors, and the patterns. They can also be obtained for holographic viewing devices and glasses.
Significantly, AR fireworks are completely safe as there are no explosions and air pollution, and even the sound can be reduced to make the entire experience less intimating. Judging from the number of cities and communities that have returned to traditional fireworks, however, the future of augmented reality fireworks might be limited.
Thank an Engineer
Modern fireworks displays continue to incorporate cutting-edge technology and innovation. The combination of chemistry, physics, electronics, and computer simulations used in creating aerial explosions and starbursts is truly impressive. Add in laser and drone technologies, and the results are amazing. Take a moment to appreciate the engineers and technicians who make it all possible.