Supercavitation is the use of cavitation effects to create a large bubble of gas inside a liquid, allowing an object to travel at great speed through the liquid by being wholly enveloped by the bubble. The cavity (the bubble) reduces the drag on the object and this makes supercavitation an attractive technology; drag is normally about 1,000 times greater in water than in air. This article or section does not cite any references or sources. ... Soap bubbles Bubble may refer to: Soap bubble, spherical liquid film, also possibly of bubble gum Cavitation, pocket of air caught in a liquid Bubble (economics), where speculation causes prices to rise to unsustainable levels a (normally) transparent dome Light bulb, in theater lighting terminology [1] in poker tournaments, the... This article or section does not cite its references or sources. ... A liquid will usually assume the shape of its container A liquid is one of the main states of matter. ... This article or section does not cite its references or sources. ... An object falling through a gas or liquid experiences a force in direction opposite to its motion. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... Layers of Atmosphere - not to scale (NOAA)[2] Earths atmosphere is a layer of gases surrounding the planet Earth and retained by the Earths gravity. ...

A cavitation forms behind an object passed by a rapidly streaming liquid

Image File history File links Download high resolution version (1856x828, 12 KB) Description: Schema: Superkavitation in schnell strömender Flüssigkeit Source: http://de. ... Image File history File links Download high resolution version (1856x828, 12 KB) Description: Schema: Superkavitation in schnell strömender Flüssigkeit Source: http://de. ...

From cavitation to supercavitation

To hydroengineers, cavitation is a known phenomenon. Cavitation happens when water pressure is lowered below its vapor pressure or vapor pressure is increased to water pressure. This often happens at extremely high speed though can happen at any speed and even when still. Cavitation occurs inside a pump or around an obstacle, such as a rapidly spinning propeller or in a body of liquid (such as a kettle) due to temperature and/or pressure change. The pressure of the fluid can drop due to its high speed (Bernoulli's principle) and when the pressure drops below the vapor pressure of the water or the temperature increases thus vapor pressure increses reaching water pressure, it vaporizes — typically forming small bubbles of water vapour, (water in its gas phase). In ordinary hydrodynamics, cavitation is a mostly unintended and undesirable phenomenon: the bubbles are typically not sustained but implode as they and the water around them suddenly slows down again, with a resulting sudden rise in ambient pressure. These small implosions can even lead to physical damage, for instance to badly designed rotating propellers. This article or section does not cite any references or sources. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... The use of water pressure - the Captain Cook Memorial Jet in Lake Burley Griffin, Canberra. ... Bernoullis Principle states that in an ideal fluid (low speed air is a good approximation), with no work being performed on the fluid, an increase in velocity occurs simultaneously with decrease in pressure or gravitational energy. ... In chemistry and physics, Vapor pressure is the pressure of a vapor in equilibrium with its non-vapor phases. ... Boundaries: Phase, Pressure, Temperature Evaporation/Sublimation Whenever a water molecule leaves a surface, it is said to have evaporated. ... This article or section does not cite its references or sources. ... Hydrodynamics is fluid dynamics applied to liquids, such as water, alcohol, oil, and blood. ...

A supercavitating object uses this phenomenon in a much larger (and sustained) manner (hence the name supercavitation). A supercavitating object's main features are a specially shaped nose, typically flat with sharp edges, and a streamlined, hydrodynamic and aerodynamic shape. When the object is traveling through water at speeds of above roughly one-hundred miles per hour, the nose deflects the water outward so fast that it flies free of the surface. Water pressure takes time to collapse the wall of the resulting cavity, hence the nose opens an extended bubble of water vapor. Given sufficient speed, or by the injection of gas into a partially-developed bubble, the cavity can extend to envelop the entire body of the object. A supercavitating object quite literally 'flies' through the surrounding gas. Aerodynamics is a branch of fluid dynamics concerned with the study of gas flows, first analysed by George Cayley in the 1800s. ...

Various underwater methods of propulsion have been proposed to reach the necessary speed, with a possible concept being a rocket engine burning aluminum with water. A conventional rocket engine is used to propel the Shkval supercavitating torpedo. Aluminum is a soft and lightweight metal with a dull silvery appearance, due to a thin layer of oxidation that forms quickly when it is exposed to air. ... The VA-111 Shkval torpedo and its descendants are supercavitating torpedoes, developed by the Russian navy, which are capable of speeds of several hundred knots. ...

Current applications

The supercavitation principle is being used for very high performance supercavitating propellers and also for control surfaces such as rudders. The supercavitating propeller is a variant of a propeller for propulsion in water, where cavitation (formation of water vapour) is actively employed to gain increased speed by reduced friction. ... Stern-mounted steering oar of an Egyptian riverboat depicted in the Tomb of Menna (c. ...

In 1940, Herbert A. Wagner - Head of the Development Department for Guided Missiles at Henschel Flugzeugwerke (HFW), Berlin - started the development of two Guided Air-to-Sea Missiles: the Henschel Hs 293 and the larger Henschel Hs 294. Both missiles were supposed to be guided to a point in front of the water line of a ship. At water entry, the warhead would separate from fuselage and wings. Using its remaining kinetic energy, the (unguided) warhead-projectile would then follow an underwater path towards the ship target. The projectile body had a slender conical shape with an ogive nose. The underwater path could be curved slightly upward by means of a small ridge on the upper side of the ogive. The projectile had to be curved upward in order to achieve a nearly horizontal path at the point of impact. In order to stabilize the projectile under water within its supercavity bubble, a somewhat larger cone angle was used at the tail of the body. Tests with prototypes of the Hs 294 achieved velocities at water entry of approximately 150 to 180 m/s. Those values were corresponding with underwater paths of the warhead-projectile of about 60 to 80 meters. This article does not cite its references or sources. ... Trent Henschel- A young player with an ugly face from the Adelaide Crows (see Crows), he was known as Trent Potential until the day when it became apparant that he lacked potential. ... The Henschel Hs 293 was a German guided glide bomb used against ships during World War II. History The Hs 293 project was started in 1940, based on the Gustav Schwartz Propellerwerke glide bomb which was designed in 1939. ... The Henschel Hs 294 was a torpedo. ... An ogive is a curved shape, figure, or feature. ...

After World War II and until 2004, Russian Shkval torpedoes were the only publicly known application of supercavitation technology applied to an entire underwater vessel. The gas bubble these torpedoes fly in is formed partly due to the shape of the torpedo body, partly by rocket exhaust diverted to a nozzle on the front of the torpedo. Combatants Allied powers: China France Great Britain Soviet Union United States and others Axis powers: Germany Italy Japan and others Commanders Chiang Kai-shek Charles de Gaulle Winston Churchill Joseph Stalin Franklin Roosevelt Adolf Hitler Benito Mussolini Hideki Tōjō Casualties Military dead: 17,000,000 Civilian dead: 33,000... 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... Artists impression of a Shkval torpedo. ...

In 2004 the German weapons manufacturer Diehl BGT Defence announced their own supercavitating torpedo called the Barracuda. (English translation) Diehl BGT Defence GmbH & Ko KG is a German arms manufacturer with headquarters in Ãœberlingen. ...

Beginning in 1994, the US Navy began developing a sea mine clearance system known as RAMICS (Rapid Airborne Mine Clearance System), based on a supercavitating projectile, invented by C Tech Defense Corporation, that was stable in both air and water. These have been produced in .50cal (12.7mm), 20mm (.79"), and 30mm (1.19") [1]. The terminal ballistic design of the projectile allowed it to cause explosive destruction of sea mines as deep as 45 m (140 feet) underwater with a single round. (C Tech) In 2000 these projectiles were used to successfully destroy a range of live underwater mines when fired from a hovering Sea Cobra gunship at the Aberdeen Proving Grounds in Maryland. RAMICS is currently undergoing further development under a contract to Northrop Grumman for introduction into the fleet.

The darts of German (Heckler & Koch P11) and Russian underwater firearms [2], and other similar weapons are also supercavitating. The HK P11 is a special-purpose Heckler & Koch pistol designed to be used underwater, where ordinary-shaped bullets are inaccurate and have a very short range. ... Caliber: 5. ...

In 1999 the supercavitation technology was adopted to hunting projectiles. These "SuperPenetrator" bullets feature a very stable straight line penetration in aqueous media.[3]

To date, the main emphasis of research into supercavitation has been into the development of torpedoes, due to the fact supercavitating types can give an overwhelming advantage to a navy possessing them in quantity (assuming that the opposing navy doesn't possess them). A modern torpedo, historically called a locomotive torpedo, is a self-propelled projectile that (after being launched above or below the water surface) operates underwater and is designed to detonate on contact or in proximity to a target. ...

In 2005 DARPA announced the 'Underwater Express program', a research and evaluation bid to establish the potential of supercavitation. The program's ultimate goal is a new class of underwater craft for littoral missions that can transport small groups of Navy personnel or specialized military cargo at speeds up to 100 knots. The contracts were awarded to Northrop Grumman and General Dynamics Electric Boat in late 2006.

As of early 2006, Russia and China are known operators of supercavitating weapons. Germany and the United States have in-development weapons and may be fielding operational models secretly.

Iran has claimed to have successfully tested its first supercavitation torpedo on 2 April and 3 April 2006. Some sources have speculated it is based on the Russian VA-111 Shkval Supercavitation torpedo, which travels at the same speed [4] [5] [6]. Russian Foreign Minister Sergei Lavrov denied supplying Iran with the technology [7]. Iran called this weapon the Hoot (Whale). April 2 is the 92nd day of the year (93rd in leap years) in the Gregorian calendar, with 273 days remaining. ... April 3 is the 93rd day of the year (94th in leap years) in the Gregorian calendar, with 272 days remaining. ... For the Manfred Mann album, see 2006 (album). ... Artists impression of a Shkval torpedo. ... Sergey Viktorovich Lavrov, in Russian Сергей Викторович Лавров, is the minister of foreign affairs of the Russian Federation. ... Hoot (Persian: حوت - Fish) is an Iranian underwater missile that travels at approximately 360 km/h, several times faster than a conventional torpedo. ...

Alleged applications

Josef Papp claimed in 1966 to have built an underwater propulsion system which took advantage of supercavitation to achieve incredibly high speeds.[8] However this is generally regarded as a hoax, due to circumstances surrounding his claim. In one of the most peculiar chapters in Canadian history, the story of Josef Papp and his jet submarine is still filled with controversy. ... A hoax is an attempt to trick an audience into believing that something false is real. ...

Drawbacks

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Though increasing the speed of a torpedo does theoretically confer a significant tactical advantage to the combatant employing them, supercavitation has its drawbacks as well. In short, naval tactics have evolved to the point that the use of supercavitation is not of undisputed benefit, and the navies that employ it tend to be those that have not perfected sophisticated guidance systems for their torpedoes. Naval combat frequently occurs over significant distances; the Honeywell Mk48, the U.S. Navy's staple torpedo, has a range of five miles, with unconfirmed reports of ranges in excess of twenty. The maximum speed of at least 32 miles per hour (unconfirmed reports indicate speeds upwards of 60 mph) mean it can reach its maximum range in a matter of minutes (ten to twenty, depending on the figures used). A supercavitating torpedo traveling at 230mph (though reports indicate the German Barracuda can reach speeds near 500mph) would still take over a minute to reach a destination five miles away, and around six minutes to reach a target twenty miles away. This is more than ample time for a target to avoid. Supercavitation also produces an incredible amount of noise, which alerts the target to both the torpedo and the location of the launching sub. A common submarine tactic is to quietly launch a torpedo, but not to activate it until the firing sub has moved a few hundred yards away, then activating it and guiding it to the target. Honeywell Heating Specialties Company Stock Certificate dated 1924 signed by Mark C. Honeywell - courtesy of Scripophily. ... Testing of the Mark 48: The Australian Collins class submarine, HMAS Farncomb, fired a Mark 48 torpedo at the 28-year-old destroyer escort Torrens. ...

References

• Office of Naval Research (2004, June 14). Mechanics and energy conversion: high-speed (supercavitating) undersea weaponry (D&I). Retrieved April 12, 2006, from http://www.onr.navy.mil/
• Savchenko Y. N. (n.d.). CAV 2001 - Forth Annual Symposium on Cavitation - California Institute of Technology Retrieved April 9, 2006, from http://cav2001.library.caltech.edu/159/00/Savchenko.pdf
• Hargrove, J. (2003). Supercavitation and aerospace technology in the development of high-speed underwater vehicles. In 42nd AIAA Aerospace Sciences Meeting and Exhibit. Texas A&M University.
• Kirschner et al. (2001, October) Supercavitation research and development. Undersea Defense Technologies
• Ashley, S. (2001, May). Warp drive underwater. Scientific American
• Deep Angel, (2001). Projectiles. Retrieved Apr. 12, 2006, from Projecticles Web site: http://supercavitation.com/html/projectiles.html
• Miller, D. (1995). Supercavitation: going to war in a bubble. Jane's Intelligence Review. Retrieved Apr 14, 2006, from http://www.janes.com/
• Graham-Rowe, & Duncan. (2000). Faster than a speeding bullet. NewScientist, 167(2248), 26-30.
• VA-111 Shkval. (2006, April 7). In Wikipedia, The Free Encyclopedia. Retrieved April 11, 2006, from http://en.wikipedia.org/wiki/VA-111_Shkval

External links

• Deep Angel — Science fiction website centered around envisaged supercavitation technology
• (German) German weapons design site about their supercavitating torpedo (English translation)
• Diehl BGT Defence's "Barracuda" - a german supercavitating Torpedo
• DARPA Underwater Express Program
• Global Security.org on Supercavitation