Nuclear marine propulsion
Nuclear marine propulsion is propulsion of a ship or submarine with heat provided by a nuclear power plant. The power plant heats water to produce steam for a turbine used to turn the ship's propeller through a gearbox or through an electric generator and motor. Naval nuclear propulsion is used within naval warships such as supercarriers. A small number of experimental civil nuclear ships have been built. Compared to oil or coal fuelled ships, nuclear propulsion offers the advantages of long intervals of operation before refueling. All the fuel is contained within the nuclear reactor, so no cargo or supplies space is taken up by fuel, nor is space taken up by exhaust stacks or combustion air intakes. However, the low fuel cost is offset by the high operating costs and investment in infrastructure, so nearly all nuclear-powered vessels are military ones. Naval reactors are of the pressurized water type. A primary water circuit transfers heat generated from nuclear fission in the fuel to a steam generator.
This circuit operates at a temperature of around 250 to 300 °C. Any radioactive contamination in the primary water is confined. Water is circulated by pumps; the hot water from the reactor heats a separate water circuit in the steam generator. The water passes through steam driers on its way to the steam turbine. Spent steam at low pressure is run through a condenser cooled by seawater and returns to liquid form; the water continues the cycle. Any water lost in the process can be made up by desalinated sea water added to the steam generator feed water. In the turbine, the steam expands and reduces its pressure as it imparts energy to the rotating blades of the turbine. There may be many stages of fixed guide vanes; the output shaft of the turbine may be connected to a gearbox to reduce rotation speed a shaft connects to the vessel's propellers. In another form of drive system, the turbine turns an electrical generator, the electric power produced is fed to one or more drive motors for the vessel's propellers.
The Russian, US and British navies rely on direct steam turbine propulsion, while the French and Chinese ships use the turbine to generate electricity for propulsion. Most nuclear submarines have a single reactor, but Russian submarines have two, so had USS Triton. Most American aircraft carriers are powered by two reactors; the majority of marine reactors are of the pressurized water type, although the US and Soviet navies have designed warships powered with liquid metal cooled reactors. Marine-type reactors differ from land-based commercial electric power reactors in several respects. While land-based reactors in nuclear power plants produce up to around 1600 megawatts of electrical power, a typical marine propulsion reactor produces no more than a few hundred megawatts. Space considerations dictate that a marine reactor must be physically small, so it must generate higher power per unit of space; this means. Its mechanical systems must operate flawlessly under the adverse conditions encountered at sea, including vibration and the pitching and rolling of a ship operating in rough seas.
Reactor shutdown mechanisms cannot rely on gravity to drop control rods into place as in a land-based reactor that always remains upright. Salt water corrosion is an additional problem; as the core of a seagoing reactor is much smaller than a power reactor, the probability of a neutron intersecting with a fissionable nucleus before it escapes into the shielding is much lower. As such, the fuel is more enriched than that used in a land-based nuclear power plant, which increases the probability of fission to the level where a sustained reaction can occur; some marine reactors run on low-enriched uranium which requires more frequent refueling. Others run on enriched uranium, varying from 20% 235U, to the over 96% 235U found in U. S. submarines, in which the resulting smaller core is quieter in operation. Using more-highly enriched fuel increases the reactor's power density and extends the usable life of the nuclear fuel load, but is more expensive and a greater risk to nuclear proliferation than less-highly enriched fuel.
A marine nuclear propulsion plant must be designed to be reliable and self-sufficient, requiring minimal maintenance and repairs, which might have to be undertaken many thousands of miles from its home port. One of the technical difficulties in designing fuel elements for a seagoing nuclear reactor is the creation of fuel elements which will withstand a large amount of radiation damage. Fuel elements may crack over time and gas bubbles may form; the fuel used in marine reactors is a metal-zirconium alloy rather than the ceramic UO2 used in land-based reactors. Marine reactors are designed for long core life, enabled by the high enrichment of the uranium and by incorporating a "burnable poison" in the fuel elements, depleted as the fuel elements age and become less reactive; the gradual dissipation of the "nuclear poison" increases the reactivity of the core to compensate for the lessening reactivity of the aging fuel elements, thereby lengthening the usable life of the fuel. The life of the compact reactor pressure vessel is extended by providing an internal neutron shield, which reduces the
Los Angeles the City of Los Angeles and known by its initials L. A. is the most populous city in California, the second most populous city in the United States, after New York City, the third most populous city in North America. With an estimated population of four million, Los Angeles is the cultural and commercial center of Southern California; the city is known for its Mediterranean climate, ethnic diversity and the entertainment industry, its sprawling metropolis. Los Angeles is the largest city on the West Coast of North America. Los Angeles is in a large basin bounded by the Pacific Ocean on one side and by mountains as high as 10,000 feet on the other; the city proper, which covers about 469 square miles, is the seat of Los Angeles County, the most populated county in the country. Los Angeles is the principal city of the Los Angeles metropolitan area, the second largest in the United States after that of New York City, with a population of 13.1 million. It is part of the Los Angeles-Long Beach combined statistical area the nation's second most populous area with a 2015 estimated population of 18.7 million.
Los Angeles is one of the most substantial economic engines within the United States, with a diverse economy in a broad range of professional and cultural fields. Los Angeles is famous as the home of Hollywood, a major center of the world entertainment industry. A global city, it has been ranked 6th in the Global Cities Index and 9th in the Global Economic Power Index; the Los Angeles metropolitan area has a gross metropolitan product of $1.044 trillion, making it the third-largest in the world, after the Tokyo and New York metropolitan areas. Los Angeles hosted the 1932 and 1984 Summer Olympics and will host the event for a third time in 2028; the city hosted the Miss Universe pageant twice, in 1990 and 2006, was one of 9 American cities to host the 1994 FIFA men's soccer World Cup and one of 8 to host the 1999 FIFA women's soccer World Cup, hosting the final match for both tournaments. Home to the Chumash and Tongva, Los Angeles was claimed by Juan Rodríguez Cabrillo for Spain in 1542 along with the rest of what would become Alta California.
The city was founded on September 4, 1781, by Spanish governor Felipe de Neve. It became a part of Mexico in 1821 following the Mexican War of Independence. In 1848, at the end of the Mexican–American War, Los Angeles and the rest of California were purchased as part of the Treaty of Guadalupe Hidalgo, becoming part of the United States. Los Angeles was incorporated as a municipality on April 4, 1850, five months before California achieved statehood; the discovery of oil in the 1890s brought rapid growth to the city. The completion of the Los Angeles Aqueduct in 1913, delivering water from Eastern California assured the city's continued rapid growth; the Los Angeles coastal area was settled by the Chumash tribes. A Gabrieleño settlement in the area was called iyáangẚ, meaning "poison oak place". Maritime explorer Juan Rodríguez Cabrillo claimed the area of southern California for the Spanish Empire in 1542 while on an official military exploring expedition moving north along the Pacific coast from earlier colonizing bases of New Spain in Central and South America.
Gaspar de Portolà and Franciscan missionary Juan Crespí, reached the present site of Los Angeles on August 2, 1769. In 1771, Franciscan friar Junípero Serra directed the building of the Mission San Gabriel Arcángel, the first mission in the area. On September 4, 1781, a group of forty-four settlers known as "Los Pobladores" founded the pueblo they called El Pueblo de Nuestra Señora la Reina de los Ángeles,'The Town of Our Lady the Queen of the Angels'; the present-day city has the largest Roman Catholic Archdiocese in the United States. Two-thirds of the Mexican or settlers were mestizo or mulatto, a mixture of African and European ancestry; the settlement remained a small ranch town for decades, but by 1820, the population had increased to about 650 residents. Today, the pueblo is commemorated in the historic district of Los Angeles Pueblo Plaza and Olvera Street, the oldest part of Los Angeles. New Spain achieved its independence from the Spanish Empire in 1821, the pueblo continued as a part of Mexico.
During Mexican rule, Governor Pío Pico made Los Angeles Alta California's regional capital. Mexican rule ended during the Mexican–American War: Americans took control from the Californios after a series of battles, culminating with the signing of the Treaty of Cahuenga on January 13, 1847. Railroads arrived with the completion of the transcontinental Southern Pacific line to Los Angeles in 1876 and the Santa Fe Railroad in 1885. Petroleum was discovered in the city and surrounding area in 1892, by 1923, the discoveries had helped California become the country's largest oil producer, accounting for about one-quarter of the world's petroleum output. By 1900, the population had grown to more than 102,000; the completion of the Los Angeles Aqueduct in 1913, under the supervision of William Mulholland, assured the continued growth of the city. Due to clauses in the city's charter that prevented the City of Los Angeles from selling or providing water from the aqueduct to any area outside its borders, many adjacent city and communities became compelled to annex themselves into Los Angeles.
Los Angeles created the first municipal zoning ordinance in the United States. On September 14, 1908, the Los Angeles City Council promulgated residential and industrial land use zones; the new ordinance established three residential zones of a single type, where industrial uses were
A fire-control system is a number of components working together a gun data computer, a director, radar, designed to assist a weapon system in targetting and hitting its target. It performs the same task as a human gunner firing a weapon, but attempts to do so faster and more accurately; the original fire-control systems were developed for ships. The early history of naval fire control was dominated by the engagement of targets within visual range. In fact, most naval engagements before 1800 were conducted at ranges of 20 to 50 yards. During the American Civil War, the famous engagement between the USS Monitor and the CSS Virginia was conducted at less than 100 yards range. Rapid technical improvements in the late 19th century increased the range at which gunfire was possible. Rifled guns of much larger size firing explosive shells of lighter relative weight so increased the range of the guns that the main problem became aiming them while the ship was moving on the waves; this problem was solved with the introduction of the gyroscope, which corrected this motion and provided sub-degree accuracies.
Guns were now free to grow to any size, surpassed 10 inches calibre by the turn of the century. These guns were capable of such great range that the primary limitation was seeing the target, leading to the use of high masts on ships. Another technical improvement was the introduction of the steam turbine which increased the performance of the ships. Earlier screw-powered capital ships were capable of 16 knots, but the first large turbine ships were capable of over 20 knots. Combined with the long range of the guns, this meant that the ships moved a considerable distance, several ship lengths, between the time the shells were fired and landed. One could no longer eyeball the aim with any hope of accuracy. Moreover, in naval engagements it is necessary to control the firing of several guns at once. Naval gun fire control involves three levels of complexity. Local control originated with primitive gun installations aimed by the individual gun crews. Director control aims all guns on the ship at a single target.
Coordinated gunfire from a formation of ships at a single target was a focus of battleship fleet operations. Corrections are made for surface wind velocity, firing ship roll and pitch, powder magazine temperature, drift of rifled projectiles, individual gun bore diameter adjusted for shot-to-shot enlargement, rate of change of range with additional modifications to the firing solution based upon the observation of preceding shots; the resulting directions, known as a firing solution, would be fed back out to the turrets for laying. If the rounds missed, an observer could work out how far they missed by and in which direction, this information could be fed back into the computer along with any changes in the rest of the information and another shot attempted. At first, the guns were aimed using the technique of artillery spotting, it involved firing a gun at the target, observing the projectile's point of impact, correcting the aim based on where the shell was observed to land, which became more and more difficult as the range of the gun increased.
Between the American Civil War and 1905, numerous small improvements, such as telescopic sights and optical rangefinders, were made in fire control. There were procedural improvements, like the use of plotting boards to manually predict the position of a ship during an engagement. Sophisticated mechanical calculators were employed for proper gun laying with various spotters and distance measures being sent to a central plotting station deep within the ship. There the fire direction teams fed in the location and direction of the ship and its target, as well as various adjustments for Coriolis effect, weather effects on the air, other adjustments. Around 1905, mechanical fire control aids began to become available, such as the Dreyer Table and Argo Clock, but these devices took a number of years to become deployed; these devices were early forms of rangekeepers. Arthur Pollen and Frederic Charles Dreyer independently developed the first such systems. Pollen began working on the problem after noting the poor accuracy of naval artillery at a gunnery practice near Malta in 1900.
Lord Kelvin regarded as Britain's leading scientist first proposed using an analogue computer to solve the equations which arise from the relative motion of the ships engaged in the battle and the time delay in the flight of the shell to calculate the required trajectory and therefore the direction and elevation of the guns. Pollen aimed to produce a combined mechanical computer and automatic plot of ranges and rates for use in centralised fire control. To obtain accurate data of the target's position and relative motion, Pollen developed a plotting unit to capture this data. To this he added a gyroscope to allow for the yaw of the firing ship. Like the plotter, the primitive gyroscope of the time required substantial development to provide continuous and reliable guidance. Although the trials in 1905 and 1906 were unsuccessful, they showed promise. Pollen was encouraged in his efforts by the rising figure of Admiral Jackie Fisher, Admiral Arthur Knyvet Wilson and the Director of Naval Ordnance and Torpedoes, John Jellicoe.
Pollen continued his work, with occasional tests carried out on Royal Navy warships. Meanwhile, a group led by Dreyer designed a similar system. Although both systems were ordered for new and existing ships of the Royal Navy, the Dreyer system found most favour with the Navy in its definitive Mar
Pressurized water reactor
Pressurized water reactors constitute the large majority of the world's nuclear power plants and are one of three types of light water reactor, the other types being boiling water reactors and supercritical water reactors. In a PWR, the primary coolant is pumped under high pressure to the reactor core where it is heated by the energy released by the fission of atoms; the heated water flows to a steam generator where it transfers its thermal energy to a secondary system where steam is generated and flows to turbines which, in turn, spin an electric generator. In contrast to a boiling water reactor, pressure in the primary coolant loop prevents the water from boiling within the reactor. All LWRs use ordinary water as both neutron moderator. PWRs were designed to serve as nuclear marine propulsion for nuclear submarines and were used in the original design of the second commercial power plant at Shippingport Atomic Power Station. PWRs operating in the United States are considered Generation II reactors.
Russia's VVER reactors are similar to U. S. PWRs. France operates many PWRs to generate the bulk of its electricity. Several hundred PWRs are used for marine propulsion in aircraft carriers, nuclear submarines and ice breakers. In the US, they were designed at the Oak Ridge National Laboratory for use as a nuclear submarine power plant with a operational submarine power plant located at the Idaho National Engineering Lab. Follow-on work was conducted by Westinghouse Bettis Atomic Power Laboratory; the first purely commercial nuclear power plant at Shippingport Atomic Power Station was designed as a pressurized water reactor, on insistence from Admiral Hyman G. Rickover that a viable commercial plant would include none of the "crazy thermodynamic cycles that everyone else wants to build."The United States Army Nuclear Power Program operated pressurized water reactors from 1954 to 1974. Three Mile Island Nuclear Generating Station operated two pressurized water reactor plants, TMI-1 and TMI-2; the partial meltdown of TMI-2 in 1979 ended the growth in new construction of nuclear power plants in the United States for two decades.
The pressurized water reactor has three new Generation III reactor evolutionary designs: the AP-1000, VVER-1200, ACPR1000+, APR1400. Nuclear fuel in the reactor pressure vessel is engaged in a fission chain reaction, which produces heat, heating the water in the primary coolant loop by thermal conduction through the fuel cladding; the hot primary coolant is pumped into a heat exchanger called the steam generator, where it flows through hundreds or thousands of small tubes. Heat is transferred through the walls of these tubes to the lower pressure secondary coolant located on the sheet side of the exchanger where the coolant evaporates to pressurized steam; the transfer of heat is accomplished without mixing the two fluids to prevent the secondary coolant from becoming radioactive. Some common steam generator arrangements are single pass heat exchangers. In a nuclear power station, the pressurized steam is fed through a steam turbine which drives an electrical generator connected to the electric grid for transmission.
After passing through the turbine the secondary coolant is cooled condensed in a condenser. The condenser converts the steam to a liquid so that it can be pumped back into the steam generator, maintains a vacuum at the turbine outlet so that the pressure drop across the turbine, hence the energy extracted from the steam, is maximized. Before being fed into the steam generator, the condensed steam is sometimes preheated in order to minimize thermal shock; the steam generated has other uses besides power generation. In nuclear ships and submarines, the steam is fed through a steam turbine connected to a set of speed reduction gears to a shaft used for propulsion. Direct mechanical action by expansion of the steam can be used for a steam-powered aircraft catapult or similar applications. District heating by the steam is used in some countries and direct heating is applied to internal plant applications. Two things are characteristic for the pressurized water reactor when compared with other reactor types: coolant loop separation from the steam system and pressure inside the primary coolant loop.
In a PWR, there are two separate coolant loops, which are both filled with demineralized/deionized water. A boiling water reactor, by contrast, has only one coolant loop, while more exotic designs such as breeder reactors use substances other than water for coolant and moderator; the pressure in the primary coolant loop is 15–16 megapascals, notably higher than in other nuclear reactors, nearly twice that of a boiling water reactor. As an effect of this, only localized boiling occurs and steam will recondense promptly in the bulk fluid. By contrast, in a boiling water reactor the primary coolant is designed to boil. Light water is used as the primary coolant in a PWR. Water enters through the bottom of the reactor's core at about 548 K and is heated as it flows upwards through the reactor core to a temperature of about 588 K; the water remains liquid despite the high temperature due to the high pressure in the primary coolant loop around 155 bar. In water, the critical point occurs at 22.064 MPa.
Pressure in the primary circuit is maintained by a pressurizer, a separate vessel, conne
Refueling and overhaul
In the United States Navy and Overhaul refers to a lengthy process or procedure performed on nuclear-powered naval ships, which involves replacement of expended nuclear fuel with new fuel and a general maintenance fix-up, modernization of the entire ship. In theory, such a process could involve only refueling or only an overhaul, but nuclear refueling is combined with an overhaul. An ROH takes one to two years for submarines and up to three years for an aircraft carrier, performed at a naval shipyard. Time periods between ROHs on a ship have varied from about 5–20 years to up to 25 years. For modern submarines and aircraft carriers, ROHs are carried out about midway through their operating lifespan. There are shorter maintenance fix-ups called availabilities for ships periodically at shipyards. A lengthy refueling and modernization process for a nuclear aircraft carrier can last up to three years and be referred to as a Refueling Complex Overhaul. At a shipyard, a ship to undergo ROH goes into a drydock, closed off from the sea.
Water is evacuated from the drydock with keel blocks pre positioned under the hull, so the ship's keel area will rest on the blocks as the water is pumped out. At the end of the ROH, the drydock is refilled with water so the ship can be re-floated and removed from the dock. To start ROH, operating procedures are used to shut down and cool down the propulsion power plant to bring it to desired temperatures and other conditions. During the ROH, ship's Navy crew stand shutdown watches, civilian shipyard workers do much of the repair and installation work. During an ROH, all personnel in a maintenance work area are required to wear a hard hat. Land-based naval reactor prototype plants have undergone similar refueling and overhauls, not at a shipyard but at whatever facility they are located. In a nuclear-powered ship, the nuclear fuel is a solid inside a reactor core, inside the ship's nuclear reactor. Once a reactor core has gone critical, meaning it has been used during a reactor operation radioactive nuclear fission products have formed in the core, the core has become radioactive.
Refueling involves taking the expended core out of the reactor and putting in a new core with fresh nuclear fuel. Because it is so radioactive, removing a core with spent nuclear fuel from a reactor requires elaborate radiological handling precautions. All materials that came in contact with the critical core, including the internal surfaces and coolant water, are considered radioactively contaminated and require special radiological handling and disposal precautions. In addition to radiological training and qualification required for working in radiation areas or with radioactive materials or contamination, radiation exposure to workers is monitored to ensure maximum exposure limits are not exceeded; the overhaul includes extensive maintenance and renovation work and checks of various systems and equipment aboard the ship. A major overhaul typically includes upgrading various systems and equipment to modernize them; the work for such overhauls is planned out by engineers well in advance and new equipment is obtained for any replacements or installations.
An example of renovation work done during refueling and overhauls of submarines is the conversion of a fleet ballistic missile submarine to a guided missile submarine. Such a conversion consists of taking the 24 ballistic missiles and their silos out of the missile section in the submarine, replacing them with 154 Tomahawk cruise missiles and special operations force insertion platforms which can carry up to 66 special operations personnel; the first four Ohio-class submarines have undergone such conversions during their midlife refueling and overhauls. For more details, see Ohio-class submarine § SSBN/SSGN conversions. During an overhaul, an extensive testing program is conducted. Numerous test procedures that have been written are followed, data is recorded as required, logs of the testing are kept. Tests that can be conducted include: radiography to test critical welds, testing of fluid systems and other pressure boundaries which includes hydrostatic testing to detect any leaks, testing of electrical and mechanical setpoints for various types of equipment such as sensor input setpoints for various kinds of automatic trips and safety valve relief pressure setpoints.
At the finish of the ROH, the testing data records are bound and retained as a permanent documentation record resulting from the ROH. As the ship is readied, toward the end of the ROH, the power plant is warmed or brought back up to the desired operating temperature and pressure so it can be started when ready. Refueling and Complex Overhaul is a process for refueling and upgrading nuclear-powered aircraft carriers in the US Navy; the nuclear reactors that power some aircraft carriers use up their nuclear fuel about halfway through their desired 50-year life spans. Because carriers can last so long before being retired, they are refueled and refurbished with an RCOH to extend their usable lifetime. At the same time a ship is refueled, it is given a complex overhaul in which broken, worn or obsolete parts are repaired or replaced and systems are modernized; the modernization includes an upgrade of ship’s combat systems and warfighting capabilities, its internal distribution systems are upgraded, allowance is made for future upgrades over the ship’s remaining operational service life.
Lockheed Martin Corporation is an American global aerospace, defense and advanced technologies company with worldwide interests. It was formed by the merger of Lockheed Corporation with Martin Marietta in March 1995, it is headquartered in Maryland, in the Washington, DC, area. Lockheed Martin employs 100,000 people worldwide as of December 2017. Lockheed Martin is one of the largest companies in the aerospace, defense and technologies industry, it is the world's largest defense contractor based on revenue for fiscal year 2014. In 2013, 78% of Lockheed Martin's revenues came from military sales. In 2009 US government contracts accounted for $38.4 billion, foreign government contracts $5.8 billion, commercial and other contracts for $900 million. Lockheed Martin operates in four business segments: Aeronautics and Fire Control and Mission Systems, Space Systems; the company has received the Collier Trophy six times, including in 2001 for being part of developing the X-35/F-35B LiftFan Propulsion System, most in 2006 for leading the team that developed the F-22 Raptor fighter jet.
Lockheed Martin is developing the F-35 Lightning II and leads the international supply chain, leads the team for the development and implementation of technology solutions for the new USAF Space Fence, is the primary contractor for the development of the Orion command module. The company invests in healthcare systems, renewable energy systems, intelligent energy distribution and compact nuclear fusion. Merger talks between Lockheed Corporation and Martin Marietta began in March 1994, with the companies announcing their $10 billion planned merger on August 30, 1994; the headquarters for the combined companies would be at Martin Marietta headquarters in North Bethesda, Maryland. The deal was finalized on March 1995, when the two companies' shareholders approved the merger; the segments of the two companies not retained by the new company formed the basis for the present L-3 Communications, a mid-size defense contractor in its own right. Lockheed Martin later spun off the materials company Martin Marietta Materials.
Both companies contributed important products to the new portfolio. Lockheed products included the Trident missile, P-3 Orion maritime patrol aircraft, U-2 and SR-71 reconnaissance airplanes, F-117 Nighthawk, F-16 Fighting Falcon, F-22 Raptor, C-130 Hercules, A-4AR Fightinghawk and the DSCS-3 satellite. Martin Marietta products included Titan rockets, Sandia National Laboratories, Space Shuttle External Tank, Viking 1 and Viking 2 landers, the Transfer Orbit Stage and various satellite models. On April 22, 1996, Lockheed Martin completed the acquisition of Loral Corporation's defense electronics and system integration businesses for $9.1 billion, the deal having been announced in January. The remainder of Loral became Loral Communications. Lockheed Martin abandoned plans for a $8.3 billion merger with Northrop Grumman on July 16, 1998, due to government concerns over the potential strength of the new group. For the Mars Climate Orbiter, Lockheed Martin incorrectly provided NASA with software using measurements in US Customary force units when metric was expected.
The development of the spacecraft cost $193.1 million. In addition to their military products, in the 1990s Lockheed Martin developed the texture mapping chip for the Sega Model 2 arcade system board and the entire graphics system for the Sega Model 3, which were used to power some of the most popular arcade games of the time. In May 2001, Lockheed Martin sold Lockheed Martin Control Systems to BAE Systems. On November 27, 2000, Lockheed completed the sale of its Aerospace Electronic Systems business to BAE Systems for $1.67 billion, a deal announced in July 2000. This group encompassed Sanders Associates, Fairchild Systems, Lockheed Martin Space Electronics & Communications. In 2001, Lockheed Martin won the contract to build the F-35 Lightning II. In 2001, Lockheed Martin settled a nine–year investigation conducted by NASA's Office of Inspector General with the assistance of the Defense Contract Audit Agency; the company paid the United States government $7.1 million based on allegations that its predecessor, Lockheed Engineering Science Corporation, submitted false lease costs claims to NASA.
On May 12, 2006, The Washington Post reported that when Robert Stevens took control of Lockheed Martin in 2004, he faced the dilemma that within 10 years, 100,000 of the about 130,000 Lockheed Martin employees – more than three-quarters – would be retiring. On August 31, 2006, Lockheed Martin won a $3.9 billion contract from NASA to design and build the CEV capsule named Orion for the Ares I rocket in the Constellation Program. In 2009, NASA reduced the capsule crew requirements from the initial six seats to four for transport to the International Space Station. On August 13, 2008, Lockheed Martin acquired the government business unit of Nantero, Inc. a company that had developed methods and processes for incorporating carbon nanotubes in next-generation electronic devices. In 2009, Lockheed Martin bought Unitech. On November 18, 2010, Lockheed Martin announced that it would be closing its Eagan, Minnesota location by 2013 to reduce costs and optimize capacity at its locations nationwide. In January 2011
A naval mine is a self-contained explosive device placed in water to damage or destroy surface ships or submarines. Unlike depth charges, mines are deposited and left to wait until they are triggered by the approach of, or contact with, any vessel. Naval mines can be used offensively, to hamper enemy shipping movements or lock vessels into a harbour. Mines can be laid in many ways: by purpose-built minelayers, refitted ships, submarines, or aircraft—and by dropping them into a harbour by hand, they can be inexpensive: some variants can cost as little as US$2000, though more sophisticated mines can cost millions of dollars, be equipped with several kinds of sensors, deliver a warhead by rocket or torpedo. Their flexibility and cost-effectiveness make mines attractive to the less powerful belligerent in asymmetric warfare; the cost of producing and laying a mine is between 0.5% and 10% of the cost of removing it, it can take up to 200 times as long to clear a minefield as to lay it. Parts of some World War II naval minefields still exist because they are too extensive and expensive to clear.
It is possible for some of these 1940s-era mines to remain dangerous for many years to come. Mines have been employed as offensive or defensive weapons in rivers, estuaries and oceans, but they can be used as tools of psychological warfare. Offensive mines are placed in enemy waters, outside harbours and across important shipping routes with the aim of sinking both merchant and military vessels. Defensive minefields safeguard key stretches of coast from enemy ships and submarines, forcing them into more defended areas, or keeping them away from sensitive ones. Minefields designed for psychological effect are placed on trade routes and are used to stop shipping from reaching an enemy nation, they are spread thinly, to create an impression of minefields existing across large areas. A single mine inserted strategically on a shipping route can stop maritime movements for days while the entire area is swept. International law requires nations to declare when they mine an area, to make it easier for civil shipping to avoid the mines.
The warnings do not have to be specific. Precursors to naval mines were first invented by Chinese innovators of Imperial China and were described in thorough detail by the early Ming dynasty artillery officer Jiao Yu, in his 14th century military treatise known as the Huolongjing. Chinese records tell of naval explosives in the 16th century, used to fight against Japanese pirates; this kind of naval mine was loaded in a wooden box, sealed with putty. General Qi Jiguang made several timed, to harass Japanese pirate ships; the Tiangong Kaiwu treatise, written by Song Yingxing in 1637 AD, describes naval mines with a rip cord pulled by hidden ambushers located on the nearby shore who rotated a steel wheellock flint mechanism to produce sparks and ignite the fuse of the naval mine. Although this is the rotating steel wheellock's first use in naval mines, Jiao Yu had described their use for land mines back in the 14th century; the first plan for a sea mine in the West was by Ralph Rabbards, who presented his design to Queen Elizabeth I of England in 1574.
The Dutch inventor Cornelius Drebbel was employed in the Office of Ordnance by King Charles I of England to make weapons, including a "floating petard" which proved a failure. Weapons of this type were tried by the English at the Siege of La Rochelle in 1627. American David Bushnell developed the first American naval mine for use against the British in the American War of Independence, it was a watertight keg filled with gunpowder, floated toward the enemy, detonated by a sparking mechanism if it struck a ship. It was used on the Delaware River as a drift mine. In 1812 Russian engineer Pavel Shilling exploded an underwater mine using an electrical circuit. In 1842 Samuel Colt used an electric detonator to destroy a moving vessel to demonstrate an underwater mine of his own design to the United States Navy and President John Tyler. However, opposition from former President John Quincy Adams scuttled the project as "not fair and honest warfare." In 1854, during the unsuccessful attempt of the Anglo-French fleet to seize the Kronstadt fortress, British steamships HMS Merlin, HMS Vulture and HMS Firefly suffered damage due to the underwater explosions of Russian naval mines.
Russian naval specialists set more than 1500 naval mines, or infernal machines, designed by Moritz von Jacobi and by Immanuel Nobel, in the Gulf of Finland during the Crimean War of 1853-1856. The mining of Vulcan led to the world's first minesweeping operation. During the next 72 hours, 33 mines were swept; the Jacobi mine was designed by German-born, Russian engineer Jacobi, in 1853. The mine was tied to the sea bottom by an anchor. A cable connected it to a galvanic cell which powered it from the shore, the power of its explosive charge was equal to 14 kilograms of black powder. In the summer of 1853, the production of the mine was approved by the Committee for Mines of the Ministry of War of the Russian Empire. In 1854, 60 Jacobi mines were laid in the vicinity of the Forts Pavel and Alexander, to deter the British Baltic Fleet from attacking them, it phased out its direct competitor the Nobel mine on the insistence of Admiral Fyodor Litke. The Nobel mines were bought from Swedish industrialist Immanuel Nobel who had entered into collusion with Russian head of navy Alexander Sergeyevich Menshikov.
Despite their high cost t