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Boom (navigational barrier)

technology Maturity 11-13 Next article →

A boom is a barrier placed across water.

Siege of Londonderry boom detail
Siege of Londonderry boom detail

It helps people control or block boats. This barrier can be used for many reasons. Some booms keep boats away from a dangerous river. Other booms might make ships pay a toll to pass. In the past, they were used for war. They stopped enemy ships from entering a port.

Castillosferrol
Castillosferrol

There are different ways a boom might work. A boom usually floats on the top of the water. A chain is a different kind of barrier. A chain can float on top or sit below the water. Sometimes, people attach a chain to logs or rafts. This makes the chain act like a floating boom. This helps the barrier stay in place.

In medieval times, people used special towers for chains. These were called boom towers. A chain could be attached to these towers. This allowed people to raise or lower the barrier. They used machines like a windlass or a capstan. This meant they could let safe ships pass. They did not have to leave the water blocked all the time.

Booms were often very well guarded. People used forts or artillery batteries to protect them. Sometimes, several ships would stand near a boom. They would use their guns to stop any attacks. A very large ship could sometimes break a boom. This happened during the Battle of Vigo Bay. During the siege of Derry, sailors cut a boom using a longboat.

Castillosferrol
Castillosferrol

We can see how these barriers work in many places. In the American Civil War, a chain blocked the Mississippi River. It went from Kentucky across to Missouri. This stopped Union ships from moving through. Today, we use similar ideas for other jobs. We use booms to contain oil spills in the ocean. We also use nets to stop submarines.

Siege of Londonderry boom detail
Siege of Londonderry boom detail
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File:Siege of Londonderry boom detail.jpg
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Castillosferrol.PNG
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