Current Affairs Current Affairs - 20 May 2015 - Vikalp Education

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Current Affairs - 20 May 2015

PM visits Hyundai Heavy Industries shipyard, seeks partnership
  • ULSAN (South Korea): Prime Minister Narendra Modi today visited Hyundai Heavy Industries here to seek increased partnership between Indian shipyards and the South Korean giant to ensure that India's shipbuilding industry can benefit from its expertise and experience.

    Modi, who flew in here, about 400km, from Seoul and drove 85km from the airport to Hyundai Heavy Industries (HHI), was received by Choi Kil-seon, the Chairman and CEO of HHI, and Kwon Oh-gap, the President and CEO of HHI, besides Mayor of Ulsan Kim Gi Hyeon.

    The Prime Minister, who spent about an hour, discussed various ways to expand cooperation in naval defence, LNG carrier construction and shipbuilding technology. 

    "Shipbuilding is a top priority for us," Modi told Choi.

    Modi showed particular interest in HHI's technological prowess in building a wide range of naval vessels as well as high-value added vessels such as LNG carriers. 

    India's state-run gas company GAIL is likely to place an order of 11 LNG carriers to haul LNG from the US to India for 20 years, starting 2017. 

    HHI recently signed a MoU with India-based engineering major Larsen and Tubro on technological support for construction of LNG carriers. 

    The company has undertaken a total of 30 offshore projects for India, beginning with the Mumbai offshore oil platform project in 1982. 

    Also, the company has operated construction equipment production lines in Pune since 2008. 

    HHI has specialised in shipbuilding, offshore and engineering, marine engines and machinery, electro electric systems, green energy and construction equipment. 

    Officials said India wants Korea's involvement in some of the LNG container ships. 

    Indian defence sector is also seeking enhancement of cooperation with Korea in shipbuilding.

#ModiInsultsIndia trends on Twitter: Here's why
  • #ModiInsultsIndia trends on Twitter: Here's whyNEW DELHI: Prime Minister Narendra Modi's statement during his recent three-nation tour that Indians earlier 'felt ashamed' of being born in the country has not gone down well on Twitter.

    "Earlier you felt ashamed of being born Indian," the Prime Minister had said, according to reports. "Now you feel proud to represent the country. Indians abroad had all hoped for a change in government last year," he added.

    Many users lambasted Modi for his comments and #ModiInsultsIndia was one of the top trends on Twitter.

    @TheTweetOfGod tweeted, "Just talked to Brahma. He's not ashamed to have been born Indian either."

    His comments also gave an opportunity to the opposition Congress to target him.

    Sanjay Jha of the Congress tweeted, "#ModiInsultsIndia is a worldwide top trend because it has offended the sensibilities of every Indian. A national disgrace beyond description."

    Pawan Khera, also of the Congress, tweeted, "India was not ashamed despite your shenanigans in Gujarat. India is more, much more than you can ever understand #ModiInsultsIndia"

LG Najeeb Jung meets President Pranab Mukherjee
  • LG Najeeb Jung meets President Pranab Mukherjee
    NEW DELHI: Lieutenant governor Najeeb Jung on Tuesday met President Pranab Mukherjee and briefed him about issues relating to transfer and posting of senior bureaucrats in Delhi.

    After meeting the President, LG Jung also met Union home minister Rajnath Singh and informed him about the stand-off on appointment of senior bureaucrats.

    The President is scheduled to meet Delhi CM Arvind Kejriwal later in the evening

    The confrontation over appointment of Shakuntala Gamlin as acting chief secretary of Delhi had turned into a full-blown war between the ruling AAP and Jung with Kejriwal alleging that the LG was trying to take over the administration.

    Despite Kejriwal's strong opposition, Jung had appointed her to the post on Friday.

    The AAP government on Monday directed all its officials to apprise the chief minister or Minister concerned about any oral or written direction from the LG or his office before following them.

    The LG has also hardened his stand maintaining that he was the main authority in dealing with transfers and postings of senior bureaucrats. The BJP has been severely critical of AAP government.

Third jail breaker nabbed in MP; remaining two on radar
  • Nagpur: Akash Thakur alias Golu, is the third jail breaker to be netted after being picked up from Pandhurna in Madhya Pradesh on Monday. Crime branch squad had earlier nabbed two other jail breakers Mohd Shoaib Khan and Prem Khatri alias Nepali and one Uttar Pradesh-based criminal last week.

    Two other fugitives, Satyendra Gupta alias Rahul and Bisen Singh Uikey, are already on police radar and likely to be tracked down soon. The five prisoners had escaped from Nagpur central jail on March 31.

    A squad of crime branch under PI Chandrashekar Dhole and Girish Tattod and assistant PI Mangesh Desai spearheaded the covert operation to nab Thakur. Sources stated that the crime branch squad, under additional CP Shrikant Tarwade and DCP Deepali Masirkar, had already left for Pandhurna on Sunday after learning that from the arrested duo, Khan and Khatri, that Thakur may be holed up there along with others.

    Sources stated that Thakur had grown beard in an attempt to look different. The Whatsapp images available with the undercover cops and Thakur's present look had left them baffled. Thakur also tried to mislead the cops by claiming his name as 'Gaurav' from Chandrapur.

    It was reliably learnt that the cops disguised themselves as farmers, tourists and local citizens while conducting searches at markets, lanes, malls, bus stops and other places until they traced Thakur on the highway along the city. The cops had fanned out to different parts of the city but maintained coordination. They tried to befriend Thakur who started replying evasively before giving up.

    Police stated that Thakur and others had gone on different trails after the firing incident at Beitul where the five had shot at a constable during checking. The fugitives were being sheltered by local criminals and helped them with cash and other logistics support. Some of these criminals were befriended by the fugitives while being in Nagpur central jail.

Air India plane with 169 on board makes emergency landing
  • Air India plane with 169 on board makes emergency landingBHUBANESWAR: A Delhi-Bhubaneswar Air India flight (AI 873) made an emergency landing at Lucknow airport with 169 passengers onboard at about 12.30 pm on Tuesday. All the passengers were safe after the landing.

    Airport sources here said that there was minor crack in the windshield forcing the pilot to land at Lucknow airport. The flight left Delhi at 11.30 am and was to land in Bhubaneswar at 1.15 pm.

    According to airport officials the flight AI 873 was flying thousands of feet above Khajuraho when the pilot detected a crack on the rear side of the nose. It was 11.57 am when the pilot finally decided to contact the air traffic control at the Amausi airport. 

    Airport director SC Hota said that the flight eventually made a safe landing at around 12.35 pm. "All passengers are safe. The aircraft is being attended by the engineers. If the problem is found to be major the passengers would be sent through an alternate flight. Otherwise the same flight will take off," he said. 
    Relatives of passengers are having an anxious moment at the airport.

    "There was some technical failure which forced the pilot to choose Lucknow airport for an emergency landing. The reason of technical failure is being investigated," said Biju Patnaik airport director Sharad Kumar.

    CEO, Indian Metals and Ferro Alloys (IMFA) Limited, Subhrakanta Panda, who was in the flight tweeted, "Air India flight to Bhubaneswar diverted to Lucknow due to a cracked windshield. First emergency diversion in all my years of flying. Just caught a glimpse. It was hardly a crack and more like a shattered windshield! Have to commend pilots for cool, professional approach".

No LTC in case of posting in home town: Govt
  • No LTC in case of posting in home town: GovtNEW DELHI: Employees who are posted in their home town cannot take Leave Travel Concession (LTC), the Centre has said. 

    "Government employees whose headquarters or place of posting and home town are one and the same are not eligible for home town LTC," it said. 

    Besides, these employees cannot convert home town LTC to avail special concession scheme to travel to North-East region, Jammu and Kashmir, and Andaman and Nicobar Islands, the Department of Personnel and Training said in an order. 

    However, government employees whose headquarters are Delhi and reside in cities or towns outside the national capital and falling in other states of National Capital Region (NCR) are eligible for home town concession, the order said.

    Every new recruit in government service is required to declare his or her home town to avail the benefits of LTC. 

    The LTC allows grant of leave and ticket reimbursement to eligible central government employees to travel to their home towns. 

    However, the government has recently allowed employees to visit North-East region and Jammu and Kashmir, among others, in order to promote tourism and increase people-to-people contact. 

Indian subcontinent's quake-causing collision course
  • When an unstoppable force like the Indian subcontinent crashes into an immovable object like the Eurasian plate, the consequences include the tallest mountains in the world and a cadence of earthquakes like the magnitude 7.8 one that struck Nepal last month and a major aftershock in the same region last week.

    Many of the geological questions about the collision remain unanswered. How did the Indian subcontinent get so quickly to where it is today? How big was India originally? Even the simplest of questions — when did India meet Eurasia, the tectonic plate that Europe and Asia sit on? — is up for debate, with researchers offering answers that differ by some 30 million years.

    "It's going to be hard to convince anyone," said Oliver E. Jagoutz, a geologist at M.I.T. and part of a team that outlined its ideas about the collision in the journal Nature Geoscience.

    Another mystery is why India is still moving at a quick pace — one and a half to two inches a year — driving the devastating earthquakes.

    "That is one of the biggest problems that we have in plate tectonics," said Douwe J.J. van Hinsbergen, a professor of earth sciences at Utrecht University in the Netherlands. "It may not seem much, but it's the rate at which your fingernails grow."

    The geologists are like accident investigators trying to decipher what happened from the wreckage, pondering how rocks from the ocean floor ended up high in the Himalayas. Much of the evidence, namely the chunk of India that is now jammed under Tibet and the Himalayas, is out of reach.

    Still, until about a decade ago, scientists thought they had the story essentially figured out.

    Throughout Earth's four-and-a-half-billion-year history, the hulking chunks of land have alternated between periods of combining into supercontinents like Pangea 300 million years ago and periods like today when they are moving apart.

    At the height of the age of dinosaurs, Pangea had broken into two giant continents, Laurasia and Gondwana, and India was a piece of Gondwana, in the Southern Hemisphere, attached to Antarctica and nestled between Africa and Australia.

    More than 100 million years ago, India broke away and accelerated northward. According to the widely accepted picture, that runaway continental fragment collided with Eurasia 50 million to 55 million years ago in one of the few places today where a piece of continent runs into a continent rather than an ocean plate.

    But not all of the pieces of the conventional wisdom fit together.

    New analyses of the magnetism preserved in rocks suggested that the southern edge of Eurasia was farther north than some had thought, raising the question of whether India was close enough to make contact with Asia by then.

    "In the old days, we thought that when India collided with southern Asia, southern Tibet was 2,000 kilometers south of where it is now," said Peter H. Molnar, a professor of geological sciences at the University of Colorado. "And that all made sense. If you collide 40 to 50 million years ago, and southern Asia was down there, you have one collision, bang, you're done."

    The revised magnetic measurements suggest that southern Tibet was 1,000 kilometers south at most. "Suddenly you have this huge space," Dr. Molnar said. "Where was India 50 million years ago? Well, India was way south of where southern Asia was. So you have a choice: You have to make northern India be enormous or you have to put an ocean in there."

    Others pointed out that the most obvious effects of a continental collision, like the raising of the Tibetan plateau, did not start until later, perhaps 10 million years later. The rocks in the western Himalaya region also point to two collisions, not one.

    "The jury was in," said Simon L Klemperer, a geophysicist at Stanford. "The jury is out again."

    Another key question: How much of India has disappeared? If the collision occurred more than 50 million years ago, almost 2,000 miles of India must have been pushed under Asia. A piece of continent this large would appear to be too big to fit the available space in ancient Gondwana.

    And yet scientists agree that something collided 50 million to 55 million years ago, clearly seen in an uplifted seafloor of this age in the northern Himalaya region.

    "That is why people said there is a collision between two continents," Dr. van Hinsbergen said. "Which is true. That is the best conclusion you can draw. The question is not so much whether there is a continent colliding 50 million years ago. The question is whether that is India."

    In 2007, Jonathan Aitchison, now a professor of geosciences at the University of Queensland in Australia, put together an alternative timeline. The collision that people thought was India meeting Asia was actually India running into an arc of islands south of Asia, and India then pushed these islands like a snowplow into Asia 20 million years later. "We believe the evidence shows India bumped into other things before Asia," Dr. Aitchison said.

    His hypothesis was widely dismissed.

    Dr. van Hinsbergen came up with a different idea. He proposed that 70 million to 120 million years ago, India split in two as it was moving north. The first piece reached Asia 50 million to 55 million years ago, as dictated by the conventional picture, but the main part lagged behind, not colliding until 20 million to 25 million years ago.

    That would make India small enough to fit into Gondwana. Tectonic plates are known to break apart — India was once connected to Madagascar, before splitting away in its northward sprint — but other scientists are skeptical, citing the lack of any geological evidence of an ocean crust separating two pieces of India.

    Dr van Hinsbergen replies that missing ocean crust is no more unlikely than missing continent. "Whatever was there disappeared without a trace," he said. "Then the question is, what was it?"

    Dr van Hinsbergen does not find the island arc hypothesis compelling, and Dr Aitchison is equally unconvinced by the suggestion of India breaking in two before colliding with Asia.

    Dr. Jagoutz and Leigh H. Royden, a professor of geology and geophysics at MIT. looking at rocks in the western Himalaya, have come to a conclusion similar to Dr. Aitchison's — that India ran into an island arc before it hit Asia — put the second collision about five million years earlier.

    In the Nature Geoscience paper, Dr Royden and Dr. Jagoutz show that the island arc could explain the swiftness of India's travels. About 80 million years ago, India was barreling north at half a foot a year, a pace it maintained for 30 million years.

    Generally, the motion of continents is driven by subduction zones — where one tectonic plate passes beneath another and then descends into the Earth's mantle, pulling everything behind it.

    Geologists knew there was one subduction zone where the Indian plate dived under Asia. With an island arc between Asia and India, there would have been two subduction zones pulling on India, which could explain the high velocity of India.

    But none of this explains why India is still so moving so fast. Whatever was north of India has long since disappeared into the mantle, and continental crust does not provide the same downward pull.

    "It's yet to be resolved what keeps India moving to the north," Dr. Royden said. "At the moment, it's still a work in progress."

    Geologists will be hard pressed to deduce what happened to India from the seismological data. Dr. Klemperer says he hopes that the mix of helium isotopes in geothermal springs will help tell whether the mantle below the Himalayan crust is part of the Indian plate or Asian plate.

    "I agree the jury should still be out," Dr. Klemperer said. "If I want to hold onto my view, then I need to eventually be able to demolish the arguments."

ISC topper scores 399 out of 400
  • NEW DELHI/KOLKATA: Kolkata, Bangalore and Mumbai shared honours as students registered all time high scores in the class X and XII results conducted by the Council for the Indian School Certificate Examinations, led by a Kolkata boy who had a near-perfect 99.75% in the class XII exam.

    Arkya Chatterjee of Kolkata's Vivekananda Mission School scored 399 out of 400 in his best-of-four subjects, beating the previous highest of 398 registered in 2012. Arkya had three perfect scores — 100 out of 100 in Mathematics, Physics and Computer Science.

    So, where did Arkya 'slip'? "A 99 out of 100 in English," said the 18-year-old, with a shy smile. He also notched up 99 in Chemistry.

    A Barcelona supporter and die-hard Messi fan, Arkya told TOI he spent 10 to 12 hours a day preparing for the board exams. "I am a little undecided between taking up pure science for graduation or going for engineering. Given a chance I would love to study physics at IISc, Bangalore," he said.

    The overall pass percentage in ISC (class XII) was 96.28, up by 1.01% from 2014. South India continued to dominate the pass percentages, registering 99.08 (English plus best three subjects).

    The commerce toppers this year were S Kavya from Vidya Niketan School, Bangalore, and Rounak Agarwal of Delhi Public School Megacity, Kolkata, who scored 99.50%. Priyanka Sen of G D Birla Centre for Education, Kolkata, with a score of 99.50% was the arts topper for 2015.

    The familiar story of girls beating boys continued. The girls' pass percentage in ISC was 97.24 as against the boys' 94.29. A total of 71,141 candidates appeared for the exams conducted in 52 written subjects. The maximum number of candidates were from the northern region. The southern region, though, had the highest percentage of girls, 49.49, who had appeared for the examination.

    A total of 138 candidates with special difficulties took the exam, of which six dyslexic candidates and four visually challenged scored over 90%. One of the four candidates who took their exams from hospital also scored more than 90%.

    The northern region, where Delhi/NCR falls, was fourth in overall pass percentage among the five regions, registering 96.04%. The north topper was Rupal Goel of Holy Child School, Ghaziabad who scored 99% in commerce.

    The council also announced the class X results on Monday, whose overall pass percentage registered a marginal increase. The overall pass percentage was 98.49 up by 0.21% from 2014. Girls' pass percentage was 98.95 as opposed to 98.12 among boys. South zone again topped with 99.66 pass percentage.

    The top position was being shared by three candidates — Sougata Chowdhury, St Xavier's Collegiate School, Kolkata, Ananya Harshad Patwardhan, Chatrabhuj Narsee Memorial School, Mumbai, and Tezan Tapan Sahu, St Mary's ICSE School, Navi Mumbai, all scoring 99.2% (496/500).

    The topper from Delhi/NCR region was Harshita Choudhary of Sri Ram School, Gurgaon, scoring 98.8%. The pass percentage of Delhi/NCR region was 98.50%.

    Category wise results have also improved significantly, with 97.18% of the SC, 96.48% of ST and 98.28% of the OBC candidates qualifying the class X exam. Similarly 95.02% of SC, 93.22% of ST and 95.71% of OBC candidates qualified the class XII exam.

Classification of Missile
  • Missiles are generally classified on the basis of their Type, Launch Mode, Range, Propulsion, Warhead and Guidance Systems.
    Cruise Missile
    Ballistic Missile
    Launch Mode:
    Surface-to-Surface Missile
    Surface-to-Air Missile
    Surface (Coast)-to-Sea Missile
    Air-to-Air Missile
    Air-to-Surface Missile
    Sea-to-Sea Missile
    Sea-to-Surface (Coast) Missile
    Anti-Tank Missile
    Short Range Missile
    Medium Range Missile
    Intermediate Range Ballistic Missile
    Intercontinental Ballistic Missile
    Solid Propulsion
    Liquid Propulsion
    Hybrid Propulsion
    Guidance Systems:
    Wire Guidance
    Command Guidance
    Terrain Comparison Guidance
    Terrestrial Guidance
    Inertial Guidance
    Beam Rider Guidance
    Laser Guidance
    RF and GPS Reference
    On the basis of Type:
    (i) Cruise Missile: A cruise missile is an unmanned self-propelled (till the time of impact) guided vehicle that sustains flight through aerodynamic lift for most of its flight path and whose primary mission is to place an ordnance or special payload on a target. They fly within the earth’s atmosphere and use jet engine technology. These vehicles vary greatly in their speed and ability to penetrate defences.ICBMCruise missiles can be categorised by size, speed (subsonic or supersonic), range and whether launched from land, air, surface ship or submarine.
    Depending upon the speed such missiles are classified as:
    1) Subsonic cruise missile
    2) Supersonic cruise missile
    3) Hypersonic cruise missile
    Subsonic cruise missile flies at a speed lesser than that of sound. It travels at a speed of around 0.8 Mach. The well-known subsonic missile is the American Tomahawk cruise missile. Some other examples are Harpoon of USA and Exocet of France.
    Supersonic cruise missile travels at a speed of around 2-3 Mach i.e.; it travels a kilometre approximately in a second. The modular design of the missile and its capability of being launched at different orientations enable it to be integrated with a wide spectrum of platforms like warships, submarines, different types of aircraft, mobile autonomous launchers and silos. The combination of supersonic speed and warhead mass provides high kinetic energy ensuring tremendous lethal effect. BRAHMOS is the only known versatile supersonic cruise missile system which is in service.
    Hypersonic cruise missile travels at a speed of more than 5 Mach. Many countries are working to develop hypersonic cruise missiles. BrahMos Aerospace is also in the process of developing a hypersonic cruise missile, BRAHMOS-II, which would fly at a speed greater than 5 Mach.
    (ii) Ballistic Missile: A ballistic missile is a missile that has a ballistic trajectory over most of its flight path, regardless of whether or not it is a weapon-delivery vehicle. Ballistic missiles are categorised according to their range, maximum distance measured along the surface of earth’s ellipsoid from the point of launch to the point of impact of the last element of their payload. The missile carry a huge payload. The carriage of a deadly warhead is justified by the distance the missile travels. Ballistic missiles can be launched from ships and land based facilities. For example, Prithvi I, Prithvi II, Agni I, Agni II and Dhanush ballistic missiles are currently operational in the Indian defence forces.
    On the basis of Launch Mode:
    (i) Surface-to-Surface Missile: A surface-to-surface missile is a guided projectile launched from a hand-held, vehicle mounted, trailer mounted or fixed installation. It is often powered by a rocket motor or sometimes fired by an explosive charge since the launch platform is stationary.
    (ii) Surface-to-Air Missile: A surface-to-air missile is designed for launch from the ground to destroy aerial targets like aircrafts, helicopters and even ballistic missiles. These missiles are generally called air defence systems as they defend any aerial attacks by the enemy.
    (iii) Surface (Coast)-to-Sea Missile: A surface (coast)-to-sea missile is designed to be launched from land to ship in the sea as targets.
    (iv) Air-to-Air Missile: An air-to-air missile is launched from an aircraft to destroy the enemy aircraft. The missile flies at a speed of 4 Mach.
    (v) Air-to-Surface Missile: An air-to-surface missile is designed for launch from military aircraft and strikes ground targets on land, at sea or both. The missiles are basically guided via laser guidance, infrared guidance and optical guidance or via GPS signals. The type of guidance depends on the type of target.
    (vi) Sea-to-Sea Missile: A sea-to-sea missile is designed for launch from one ship to another ship.
    (vii) Sea-to-Surface (Coast) Missile: A sea-to-surface missile is designed for launch from ship to land based targets.
    (viii) Anti-Tank Missile: An anti-tank missile is a guided missile primarily designed to hit and destroy heavily-armoured tanks and other armoured fighting vehicles. Anti-tank missiles could be launched from aircraft, helicopters, tanks and also from shoulder mounted launcher.
    On the basis of Range:
    This type of classification is based on maximum range achieved by the missiles. The basic classification is as follows:
    (i) Short Range Missile
    (ii) Medium Range Missile
    (iii) Intermediate Range Ballistic Missile
    (iv) Intercontinental Ballistic Missile
    On the basis of Propulsion:
    (i) Solid Propulsion: Solid fuel is used in solid propulsion. Generally, the fuel is aluminium powder. Solid propulsion has the advantage of being easily stored and can be handled in fuelled condition. It can reach very high speeds quickly. Its simplicity also makes it a good choice whenever large amount of thrust is needed.
    (ii) Liquid Propulsion: The liquid propulsion technology uses liquid as fuel. The fuels are hydrocarbons. The storage of missile with liquid fuel is difficult and complex. In addition, preparation of missile takes considerable time. In liquid propulsion, propulsion can be controlled easily by restricting the fuel flow by using valves and it can also be controlled even under emergency conditions. Basically, liquid fuel gives high specific impulse as compared to solid fuel.
    (ii) Hybrid Propulsion: There are two stages in hybrid propulsion – solid propulsion and liquid propulsion. This kind of propulsion compensates the disadvantages of both propulsion systems and has the combined advantages of the two propulsion systems.
    (iii) Ramjet:  A ramjet engine does not have any turbines unlike turbojet engines. It achieves compression of intake air just by the forward speed of the air vehicle. The fuel is injected and ignited. The expansion of hot gases after fuel injection and combustion accelerates the exhaust air to a velocity higher than that at the inlet and creates positive push. However, the air entering the engine should be at supersonic speeds. So, the aerial vehicle must be moving in supersonic speeds. Ramjet engines cannot propel an aerial vehicle from zero to supersonic speeds.
    (iv) Scramjet: Scramjet is an acronym for Supersonic Combustion Ramjet. The difference between scramjet and ramjet is that the combustion takes place at supersonic air velocities through the engine. It is mechanically simple, but vastly more complex aerodynamically than a jet engine. Hydrogen is normally the fuel used.
    (v) Cryogenic: Cryogenic propellants are liquefied gases stored at very low temperatures, most frequently liquid hydrogen as the fuel and liquid oxygen as the oxidizer. Cryogenic propellants require special insulated containers and vents which allow gas to escape from the evaporating liquids. The liquid fuel and oxidizer are pumped from the storage tanks to an expansion chamber and injected into the combustion chamber where they are mixed and ignited by a flame or spark. The fuel expands as it burns and the hot exhaust gases are directed out of the nozzle to provide thrust.
    On the basis of Warhead:
    (i) Conventional Warhead: A conventional warhead contains high energy explosives. It is filled with a chemi al explosive and relies on the detonation of the explosive and the resulting metal casing fragmentation as kill mechanisms.
    (ii) Strategic Warhead: In a strategic warhead, radio active materials are present and when triggered they exhibit huge radio activity that can wipe out even cities. They are generally designed for mass annihilation.
    On the basis of Guidance Systems:
    (i) Wire Guidance: This system is broadly similar to radio command, but is less susceptible to electronic counter measures. The command signals are passed along a wire (or wires) dispensed from the missile after launch.
    (ii) Command Guidance: Command guidance involves tracking the projectile from the launch site or platform and transmitting commands by radio, radar, or laser impulses or along thin wires or optical fibres. Tracking might be accomplished by radar or optical instruments from the launch site or by radar or television imagery relayed from the missile.
    (iii) Terrain Comparison Guidance: Terrain Comparison (TERCOM) is used invariably by cruise missiles. The system uses sensitive altimeters to measure the profile of the ground directly below and checks the result against stored information.
    (iv) Terrestrial Guidance: This system constantly measures star angles and compares them with the pre-programmed angles expected on the missile’s intended trajectory. The guidance system directs the control system whenever an alteration to trajectory is required.
    (v) Inertial Guidance: This system is totally contained within the missile and is programmed prior to launch. Three accelerometers, mounted on a platform space-stabilised by gyros, measure accelerations along three mutually perpendicular axes; these accelerations are then integrated twice, the first integration giving velocity and the second giving position. The system then directs the control system to preserve the pre-programmed trajectory. This systems are used in the surface-to-surface missiles and in cruise missiles.
    (vi) Beam Rider Guidance: The beam rider concept relies on an external ground or ship-based radar station that transmits a beam of radar energy towards the target. The surface radar tracks the target and also transmits a guidance beam that adjusts its angle as the target moves across the sky.
    (vii) Laser Guidance: In laser guidance, a laser beam is focused on the target and the laser beam reflects off the target and gets scattered. The missile has a laser seeker that can detect even miniscule amount of radiation. The seeker provides the direction of the laser scatters to the guidance system. The missile is launched towards the target, the seeker looks out for the laser reflections and the guidance system steers the missile towards the source of laser reflections that is ultimately the target.
    (viii) RF and GPS Reference: RF (Radio Frequency) and GPS (Global Positioning System) are examples of technologies that are used in missile guidance systems. A missile uses GPS signal to determine the location of the target. Over the course of its flight, the weapon uses this information to send commands to control surfaces and adjusts its trajectory. In a RF reference, the missile uses RF waves to locate the target.

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