十万个为什么·科学启蒙30篇（2）

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潜艇如何控制水下的深度？

Submarines control depth using ballast tanks that fill with water to sink or air to rise.
When valves open, seawater rushes in and increases the sub’s overall density beyond seawater.
To ascend, compressed air pushes water out of the tanks, making the vessel lighter than water.
Hydroplanes—small wing-like fins—tilt upward or downward to steer while moving forward.
Even tiny imbalances in weight distribution require constant fine-tuning by onboard computers.
Nuclear-powered subs can stay submerged for months because they don’t need surface air for engines.
Modern subs also use sonar to map nearby terrain and avoid underwater mountains or cliffs.
Emergency blow systems release high-pressure air instantly if the crew must surface fast.
Saltwater density changes with temperature and salinity, so depth sensors adjust continuously.
Every dive begins with careful calculations to ensure safe pressure limits for the hull.