Physics: Principles and Problems


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For use with Chapter 6

Wet Warp Speed
Posted November 1st, 2001

As transportation technology has improved over the decades, things are moving faster and faster. At one time, a carís maximum speed was around 35 miles per hour. Now, automobiles on the German autobahn exceed 120 miles per hour every day. In the past, propeller planes could barely travel faster than ground transportation, and now jet engines have now enabled aircrafts to break the sound barrier.

Watercrafts, however, have always been limited by the friction and drag from the water because water has more drag than air. This can be tested simply by sticking your hand in water and trying to wave as fast as you can. Also, try to run when you are hip-deep in water and see how much harder it is than running across dry land.

A craft completely submerged in water has 1,000 times more drag than it does if it were traveling through air. This drag results in a maximum speed of about 80 miles per hour for a submerged craft. However, scientists are finding a way around this limitation.

To achieve a new faster speed, underwater crafts use a phenomenon known as supercavitation. Supercavitation occurs when an underwater craft is enveloped in a gas bubble. This naturally occurs when water vapor forms in the wake of a fast-moving object underwater.

Engineers are developing ways to generate this gas pocket artificially and sustain it around the craft. It can be designed to be incredibly streamlined and slender, allowing it to travel smoothly through the long ellipsoid bubble. Because air causes much less drag than water, the craft does not touch the water, which results with only drag from the air Ė like a plane underwater.

However, once a craft is moving at supercavitation velocities, engineers must be absolutely sure that the craft never leaves the cavity. If the gas bubble folds and water strikes the hull, it would be like crashing a plane into the ocean at 230 miles per hour. Ivan Kirschner, an engineer at Anteonís Engineering Technology Center in Mystic, Connecticut, points out that such an even would turn the craft into "a crushed Coke can."

Scientists claim that supercavitation technology will represent a quantum leap in technology similar to what the development of the jet engine did for aircraft. The application for this underwater warp drive is mainly for the military. Supercavitation technology is a serious consideration for developing ultra-high speed submarines and torpedoes.

In fact, Russia developed a supercavitation torpedo known as the "Squall" in 1977 that can travel at speeds of 230 miles per hour. When Western countries heard about this technology, they started work on their own research. Now, the development budget in the U.S. is $50 million each year.

Use the Internet to research how submarines travel underwater. In your Science Journal, write a short story about submarines and how they travel in the ocean.



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Physics: Principles and Problems