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According to a 22 July 2000 article in the New Scientist, by Duncan Graham-Rowe, "... It's loud, it's rocket powered and it's ... the supersonic sub ... Rather than being streamlined, a supercavitating object needs a flat nose ...
the body has to be going pretty fast--at least 180 kilometres an hour, or 50 metres per second ... Then, at high speeds, the fluid is forced to flow off the edge of the nose with such speed and at such an angle that it can't wrap around the surface of the body ... [so that the sub is in] ... a single bubble or supercavity ... A supercavitating body has extremely low drag, because its skin friction almost disappears. Instead of being encased in water, it is surrounded by the water vapour in the supercavity, which has much lower viscosity and density. ... in a supercavitating vehicle, only the nose of the craft causes significant drag, because this is the only part of the body actually in contact with the water. ... The overall drag reduces enormously once you reach the supercavitating regime ... and then increases only linearly with speed. ... the early 1990s ... the Russians ... produce[d a supercavity] ... torpedo .... Called Shkval, meaning squall, it is said to be capable of speeds as high as 500 kilometres an hour. ... the US Naval Undersea Warfare Center (NUWC), in Newport, Rhode Island. ... established its own supercavitation programme ... In 1997 ... NUWC researchers announced they had gone supersonic. An unpowered projectile, with a carefully designed flat nose and fired from an underwater gun, broke the sound barrier in water. That's nearly 5400 kilometres per hour--or 1.5 kilometres per second. ... Already they aren't very far off the 2.5 kilometre-per-second speed record for conventional munitions in air ... For ... supersonic underwater travel ... , probably only a nuclear reactor is a compact enough power source. ...".
"... Eight whales beached and died
soon after the U.S. Navy conducted anti-submarine exercises off the northern Bahamas,
... Navy Cmdr. Greg Smith said the sonar tests were scheduled only one day and took place from about 1 p.m. to 5 p.m. March 15  off Abaco Island. Marine biologist Ken Balcomb of the Earthwatch environmental group said beachings began that same day and within two days at least 14 whales had grounded themselves on Abaco, Grand Bahama to the north, and Eleuthera to the south. Eight died ... the Navy planned to continue such tests. ... Naomi Rose of the Washington-based Humane Society of the United States ... said ... "These signals, depending on frequency, could travel quite a distance and could even wrap around the island, ... One could argue that they [the whales] fled the area where the sonar was being transmitted.'' ... Balcomb said the mammals included several deep-water beaked whales, goose beaked whales measuring 16-19 feet, dense beaked whales measuring 10-13 feet, baleen whales measuring up to 27 feet and some small minke whales. Michael Breynan, director of the Bahamian Fisheries Department, said ``I am not aware of any similar incident (having occurred) in the Bahamas.'' ... [Navy Cmdr.] Smith said the exercise was testing for upgrades of what the Navy calls the Directional Command Activated Sonobuoy System. The exercise involved a Navy P-3 aircraft dropping two buoys north of Abaco, one as close as 35 miles to the island, the other 70 to 75 miles from the island. One buoy emitted a sonar signal which was received by the other, and a submarine was moving between the two buoys. He said the exercise had nothing to do with low frequency active sonar, a new and controversial system that transmits sonar pulses so loud they can match the roar of a rocket launch. ...", according to a 21 March 2000 AP article by Jessica Robertson.
The office of naval research high speed undersea weapons project has three tasks: 1. supercavittation physics 2. vehicle guidance 3. vehicle control. Supercavitation phyics deals with the fundamental understanding of supercaviation, and numerical of two phase flows. Vehicle guidance deals with acoustic and non acoustic sensors, signal processing, waveform design, homing techniques ad the auto pilot and controller that are used to guide the weapon to its target.