Every July 6th, at 12:00 noon, a small rocket launched from the main balcony of the City Hall marks the official beginning of the San Fermin festival. Although it lasts only a few seconds, behind that moment lies a fascinating combination of chemistry, physics, acoustics, engineering, and complex organization.
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Aplicaciones anidadas
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The rocket measures approximately 1.20 meters in length and contains about 25 grams of black powder. This mixture, invented in China more than a thousand years ago, is mainly composed of potassium nitrate, charcoal, and sulfur. Each component plays a specific role: potassium nitrate provides the oxygen needed for the reaction, charcoal acts as the fuel, and sulfur facilitates ignition and accelerates the combustion process.
When the fuse is lit, the black powder in the rocket motor begins to burn. The reaction generates extremely hot gases that are expelled at high speed through the bottom of the rocket. According to Newton’s principle of action and reaction, these gases push the rocket upward. Within a few seconds, it reaches an altitude of several hundred meters.
Inside the rocket, there is also a fuse, a second slow-burning ignition cord. Its purpose is to delay the explosion until the rocket has risen between 500 and 1,000 meters. When the fuse reaches the explosive charge, it ignites and suddenly releases all the stored energy. Since the gases have no space to escape, the casing breaks apart abruptly, producing the characteristic blast of the Chupinazo.
Unlike other fireworks, the Chupinazo rocket is not designed to create spectacular visual effects. Its main purpose is to produce a powerful and unmistakable sound. The detonation can reach approximately 133 decibels, an intensity comparable to that of an aircraft during takeoff. The white smoke that appears afterward is caused by particles produced during combustion, which scatter light in all directions.
The stick attached to the lower part of the rocket also plays an important role. It acts as an aerodynamic stabilizer and helps maintain a straight trajectory during ascent. Without it, the rocket could spin or veer off course unpredictably.
Nothing is left to chance. Several minutes before noon, the municipal protocol coordinates the opening of the balconies, the appearance of the trumpeters and kettledrummers, the presence of the authorities, and the exact moment of the launch. After the explosion, the municipal band performs the traditional "Biribilketa" as the celebration spreads throughout the city.
The Chupinazo is much more than an explosion. It is an example of how chemistry becomes sound, physics becomes motion, and a reaction lasting only a few seconds becomes an emotion shared by thousands of people.
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In summary: The Chupinazo marks the beginning of the San Fermin festival
A rocket explodes and makes a very loud noise
People celebrate the start of the festival.
Aplicaciones anidadas
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Audio:
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· Avenida Juan Pablo II (intersection with Cataluña Avenue) · Avenida Bayona (Avenida Sancho el Fuerte)
