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How many folks knew the term "supercavitation"
Count me in. At least at a rather basic level of understanding.
Cavitation (in this setting) is typically the process of a propeller creating a low pressure area in water - low enough that the water changes state into a gas bubble. As the propeller continues to move, the low pressure area moves and the gas bubble collapses quite violently. You can pop onto your favorite video site and find plenty of videos showing this cavitation. You've probably seen one - it's the bubbles that form around a boat propeller. (Since boat propellers are typically pretty close to the surface, the gas bubbles form easier and don't collapse as violently or as completely. They often hang around forming a trail in the water.)
That collapse does several things. It makes a lot of noise in the water. So submarines do their best to avoid it, as that sound can help the enemy locate the sub. It also tends to erode the propeller, wearing it away. That shortens the usable life of a propeller. Another problem of cavitation is that it causes drag, making the propeller less efficient.
Supercavitation is what you may have seen in slow motion photography of bullets going through water or ballistics gel. The speed of the projectile creates a low pressure area and resulting gas bubble that completely surrounds the bullet. Maintaining supercavitation around anything larger than a bullet would take a significant amount of energy. And you'd also have problems with control, as control surfaces would need to extent into the water to be at all useful.
Anything else you think us liberals are too stupid to understand?
--Peter
