Ion Drive Propulsion: An Overview

Ion Drive Propulsion: An Overview TANG,YOUHENG Ion Drive propulsion, also called ion engine, which is a technology that involves gas ionization and can be used instead of standard chemicals. Give an electrical charge or ionize the gas xenon, which is like neon or helium, but heavier, the ionized gas can be electrically accelerated a speed of about 30km/s by the electric field force. When xenon ions are emitted at such high speed as exhaust from a spaceship, the spacecraft can be pushed in the opposite direction. The ion engine was firstly demonstrated by Emst Stuhliger, the German-born NASA scientist. Then at NASA Lewis Research Center (now called Glenn research center) from 1957 to the early 1960s IDP was developed in form by Harold R.Kaufman. Moreover, the ion drive propulsion was first demonstrated in space in â€Å"Space Electric Rocket Test (SERT)† I and II by NASA Lewis Research Center. The SERT-1, which is the first test was launched in July 20, 1964, proved the technology operated as predicted in space successfully. Furthermore, the second test SERT-II, which was launched on February 3rd 1970, verified the thousands of running hours operation of two mercury ion drive propulsions, though IDP were seldom used before the late 1990s. â€Å"Electric propulsion works by using electrical energy to accelerate a propellant to much higher velocities than is possible using chemical reactions. The most common propellant used in ion engines is xenon. Early ion engines used mercury and cesium, but they proved hard to work with. At room temperature, mercury is liquid and cesium is solid; they both must be heated to turn them into gases. Also, as mercury or cesium exhaust cooled, many of their atoms would condense on the exterior of the spacecraft, contaminating solar cells and instruments. Eventually researchers turned to xenon as a cleaner, simpler fuel for ion engines.† (De Felice, 1999). For IDP’s operation system, it uses an electric field to accelerate charged atoms or molecules to a high velocity. Ion thrusters generally use a cathode to generate a stream of electrons, which form an electric circuit with a positively charged ring the anode. A small magnetic field is used to aid this process (electrons spiral around the magnetic field lines, increasing the chance of electron-atom collisions). The ionized gas is accelerated out of the thruster and drifts towards an extraction grid system, so it can produce thrust. A neutraliser similar to the cathode is used to generate free electrons and balance the overall space charge of the outgoing beam so that the spacecraft does not charge itself up. To deal with this problem NASAs Deep Space 1 probe is testing a new type of ion thruster. The following description of DS-1s ion thrusters is from the official DS-1 Website: â€Å"Its ion propulsion system (IPS) utilizes a hollow cathode to produce electrons, used to ionize xenon. The Xe+ is electrostatically accelerated through a potential of up to 1280 V and emitted from the 30-cm thruster through a molybdenum grid. A separate electron beam is emitted to produce a neutral plasma beam. The power-processing unit (PPU) of the IPS can accept as much as 2.5 kW, corresponding to a peak thruster operating power of 2.3 kW and a thrust of 92 m N. Throttling is achieved by balancing thruster and Xe feed system parameters at lower power levels, and at the lowest thruster power, 500 W, the thrust is 20 m N. The specific impulse decreases from 3100 s at high power to 1900 s at the minimum throttle level. (De Felice, 1999)† Mostly, IDP is being used in aerospace application. Here are a couple of simple examples. Deep Space 1 which is a spacecraft of the NASA New Millennium Program dedicated to testing a payload of advanced, high risk technologies.Also it is the first spacecraft which used ion drive propulsion. Hayabusa which is an unmanned spacecraft developed by the Japan Aerospace Exploration Agency (JAXA) to return a sample of material from a small near-Earth asteroid named 25143 Itokawa to Earth for further analysis and used xenon ion engines Dawm which is a space probe launched by NASA on September 27, 2007, to study the two most massive objects of the asteroid belt–the protoplanet Vesta and the dwarf planet Ceres. It is the first NASA exploratory mission to use ion propulsion to enter orbits. There are three advantages of Ion Drive Propulsion which can probably explain why IDP is being used. First, it uses much less propellant than chemical rocketry so it may promise better reliability and simplicity than chemical rocketry or, from another perspective, it gets much more mileage out of a given quantity of propellant. Third, it could use 100% lunar or asteroid derived propellant. IDP can push a spacecraft up to about ten times as fast as chemical propulsion comparing IDP with chemical propulsion under the circumstances which ion propulsion is appropriate for. To sum up, the ion propulsion systems efficient use of electrical power and fuel enables modern spacecraft to travel farther, and it is cheaper than any other propulsion technology currently available. Ion drive propulsion is currently used for main propulsion on deep space probes and for station keeping on communication satellites. Ion thrusters expel ions to create thrust and can provide higher spacecraft top speeds than any other rocket which is available currently. In addition, the top speed of ion drive propulsion is startling. By using the principle of relativity, a physical situation could be analyzed from any reference frame as long as it moves with some constant speed relative to a known inertial frame. As a function of the proper time Ï„ experienced on the rocket, the acceleration of the rocket is a (Ï„),in Newtonian mechanics there is a quantity which increases the way velocity called the rapidity of the rocket . The rapidity ÃŽ ¸ will be ÃŽ ¸(Ï„)=∠« Ï„ 0 a(Ï„)dÏ„ The velocity is then v(Ï„)=tanhÃŽ ¸ . If a=g ,v(Ï„)=tanh(gÏ„) So if one year has passed on the rocket, the time on Earth will be tanh(1.05)=0.78C which means 78% of light. Since the limit of tanh is one as τ→∞, so the velocity of rocket will never get light speed. A more important limiting factor is the fuel. Fusion isnt a way around this because of E=mc^2 there is a limited energy can be calculate from a given mass of fuel. If a fraction (f) of the rocket is fuel, if all the fuel are burned, the momentum of the rocket will be ÃŽ ³m(1−f)ÃŽ ², with m the original mass. The conservation of momentum and energy give m=ÃŽ ³m(1−f)+E fuel 0=ÃŽ ³mÃŽ ²(1−f)+p fuel ÃŽ ²=−p fuel m−E fuel According the formulas and result shows that the fuel and rocket go opposite directions. To maximize ÃŽ ², make p fuel as large as possible and subject to a fixed E fuel so assume the fuel is massless with ÃŽ ² fuel =1 p fuel =−E fuel . ÃŽ ²=1−(1−f) 2 1+(1−f) 2 à £Ã¢â€š ¬Ã¢â€š ¬Ãƒ £Ã¢â€š ¬Ã¢â€š ¬ To sum up, even the fuel has 50% of the rockets original mass it just can get 3/5C. Researching in the area of ion propulsion is pushing the envelope of propulsion technology. To achieve higher power levels and speeds, longer durations advancements are being made. As new power sources become available, higher power thrusters will be developed that provide greater speed and more thrust. Nowadays, PPU and PMS technologies are being developed that will allow NASA to build lighter and more compact systems while increasing reliability. These technologies will allow humankind to explore the farthest reaches of our solar system also it will allow humankind to explore the farthest reaches which is out of our solar system. Work Cited List NASA:â€Å"New Millennium Program† http://nmp.jpl.nasa.gov/ds1/tech/ionpropfaq.html Lucian Dorneanu : â€Å"How Does Ion Drive Propulsion Work?† May 10th, 2007, 21:06 GMT http://news.softpedia.com/news/How-Does-Ion-Drive-Propulsion-Work-54439.shtml Permanent.com: â€Å"Electric Propulsion for Inter-Orbital Vehicles†Ã‚  http://www.permanent.com/space-transportation-electric.html Dennis Ward:â€Å"Electric(Ion)Propulsion†Ã‚  http://eo.ucar.edu/staff/dward/sao/fit/electric.htm

Ghost Solder

Stirrup-a loop, ring, or other contrivance of metal, wood, leather, etc. , suspended from the saddle of a horse to support the rider's foot. Her foot was stuck in the stirrup. Musket-a heavy, large-caliber smoothbore gun for infantry soldiers, introduced in the 16th century. He shot the musket. Hospitable-receiving or treating guests or strangers warmly and generously. That was a vary hospitable family. Siege-the act or process of surrounding and attacking a fortified place in such a way as to isolate it from help and supplies, for the purpose of lessening the resistance of the defenders and thereby making capture possible. Sherman’s March was a siege. Archives-documents or records relating to the activities, business dealings, etc. , of a person, family, corporation, association, community, or nation. That drawer is felled with archives Mortars-a receptacle of hard material, having a bowl-shaped cavity in which substances are reduced to powder with a pestle. Minie ball-a conical bullet with a hollow base that expanded when fired, used in the 19th century. when he shot the gun a minie ball fired. Cretin-a stupid, obtuse, or mentally defective person. He is cretin. Mellow-soft and rich, as sound, tones, color, or light. That color is mellow Percussion-a sharp blow for detonating a percussion cap or the fuze of an artillery shell. The percussion of all the gun fire hurt my ears. Conflict- Alexander dose not want to go to his dads girlfriends house in NC. And dose not want his dad to remarry his mom left him. He has to help richeson find out what happened to his family. s Climax-When Alexander goes throw the window of time and Richeson asks for his help. Resolution-Alexander helps Richeson’s and come to terms with his own past.

A Discussion on Islamic Militancy

Islam is an age old religion that espouses spirituality, and calls for a life of worship, faith work and submission to the will of a supreme being called Allah by following rules, set forth in the pillars of the Islamic faith, in the teaching found in the holy book the Koran and teachings of prophets of the faith. How then can a religion that professes such benevolence and deep spirituality and obedience be linked to acts of terrorism?Perhaps, the most common connection is found in the first pillar of Islam faith, which is; to bear witness that there is no entity worthy of worship except Allah alone, and that Muhammad was his messenger. Taken out of context and blown out of proportions perhaps, to this effect, is the concept of Jihad or a holy war (Pipes, 2002).There is no straight-out definition of what a jihad is, one holds it to be holy war waged against other Muslims who are said to be infidels due to a difference in their interpretation of the fait. On the other hand, another de finition of jihad is the call for Muslims to reject the legal armed conflict in order to attain deeper spiritual state of enlightenment. Why then does this â€Å"militant† brand of Islam thrive?Warner (2001), an American writer, columnist who focuses on Islam posits that it is due to the victories that these militant groups have achieved, that is why this radical ideology thrives. He further said that in 2004, Muslims were on top of the heap, better off that most of their world contemporaries (Warner, 2001). He also said that some Muslims feel the need to be on top again; hence this implies hostile relations with the Western world, as this is seen as the source of their problems (Warner, 2001).While there are only 10 to 15 percent of the Muslim world currently espousing this belief, with approximately one billion Muslims in the world, there are easily 100 million to 150 million of them. Coupled with misinformation, and lack of understanding of the Islamic faith, this is the r eason for such ideology to thrive among Muslims or otherwise.REFERENCESArave, L. (n.d.). Militant Islam thrives on its success. Retrieved February 18, 2009, fromhttp://209.85.175.132/search?q=cache:RvCXXjWGddIJ:findarticles.com/p/articles/mi_qn4188/is_20040206 /ai_n11439530+why+does+militant+islam+thrive&hl=tl&ct=clnk&cd=6&gl=ph

Malnutrition Essay - 1715 Words

Cassidy Burkholder Informative Paper English Comp. 1 Mr. Broadfoot 20th of November 2012 Malnutrition Around the World For most us Americans, knowing when we’re going to eat next is something we very rarely think of, and when we do think about being hungry we still know where our food is coming from. Three big meals a day, and a few snacks in between, is how most of us live. It’s hard for us to imagine what its like for those who go days eating very little or nothing at all. But unfortunately that’s how it is for most of the world and surprisingly it happens in the United Sates as well. There are many reasons malnutrition can happen, and it happens to every age group. Even though there are many ways to treat it, in the†¦show more content†¦The ten states who felt it the most were Mississippi, New Mexico, Texas, South Carolina, Louisiana, Oklahoma, Utah, Arkansas, Kentucky, and Arizona. (Haerens 36) While there are malnourished people in America, it is much worse all around the world, mostly in third world countries. There are three pred ominate reasons why third world countries are hit hard with malnutrition, 1) poor families aren’t given government help, 2) difficulties with economy and 3) higher food prices. (â€Å"2012 World Hunger†¦Ã¢â‚¬ ) As stated in the website â€Å"2012 World Hunger and Poverty Facts and Statistics,† in the world there are 925 million hungry people, most of them in Asia, the Pacific and Africa. These people live on $1.25 or less a day. Minimum wage is $7.25 in the U.S., and most people work 8 hours a day, so that means they would be getting fifty-eight dollars a day. It would take someone in a third world country about forty-seven days to make what someone makes in America in 8 hours. And most of them spend that money on food and medical needs, but $1.25 is not enough. 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