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    Space Propulsion Essay (2412 words)

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    The following is a research project on Space Vehicle Propulsion. It shallconsist of four sections, each discussing specific topics.

    Section One lays outthe basic ideas of rocketry. Section Two compares Rocket Propulsion Systems, andshows the basis for the comparison. It also shows how each specific RocketSystem works and Section Three gives a description of how Space Propulsion hasevolved and contains a conclusion. SECTION 1 The Basics Section One is a briefdescription of the basic properties of Rocket Systems. It defines the key termsand shows how a basic rocket works. It also shows the State if The Art.

    I havechosen to do my project on space vehicle propulsion. Basically, this means thatmy research shall be based primarily on rocketry. Rocketry is a way ofpropulsion that has developed in numerous ways since it was first used to propelfireworks in the 16th century. It has emerged into an extremely complicatedscience that few actually understand.

    Most space rocketry in America is used inNASA (National Aeronautics and Space Association) space projects. NASA, agovernment association that focuses on space exploration, is the main user ofrocket technology. It is used mostly to power their satellites and shuttles intospace. Pushing an object that weighs as much as a space shuttle does directlyvertical until escaping the Earths atmosphere requires a tremendous amount ofpower. This is why NASA uses rockets.

    Rockets are essentially the most powerfulforms of propulsion there is today. Space Vehicle Propulsion is based rocketengines. The basic principle of rocket engine is that when fuel is burned in theengine, the reaction mass is expelled at high speeds. As a result of Newtonslaw of action and reaction this pushes the vehicle in the opposite direction ofthe one in which the reaction mass is moving.

    Thrust is the force that theengine exerts on all space behind it in order to “push” the vehicle forward. Efficiency is the way that the quality of rocket engines is measured by. It ismeasured by the time it takes for one kilogram of propellant to create onekilogram of thrust. The goal of my research is to find out what makes theseengines more efficient. In rocketry, the state of the art is extremely hard todefine, since there are so many different forms of rocketry ranging from liquidpropellant rockets to fireworks. The state of the art though is probably nuclearpowered rockets.

    It is much more efficient because it does not use chemicalcombustion like most rockets do. Instead NFRRs (Nuclear Fission Reactor Rockets)heat hydrogen in a fission reactor which expels the propellant at blisteringspeeds. Much research is being done with NFRRs. They are still highlyexperimental because of the dangers that could be associated with them.

    TheNERVA (Nuclear Engine for Rocket Vehicle Application) was one of the mostextensive NFRR research projects, however it failed because of the inabilityfigure out an approach to putting the research into a developmental stage. SECTION 2 Specific Rocket Propulsion Systems Section One has laid the foundationfor further research in the are of rocketry. Section two shall discussproperties of efficiency in more depth, it shall lay out the types of rockets inexistence now. It shall also show which type of rocket is the most efficient. After this section, the next one shall describe how the reasons for thesespecific rockets efficiency and depending on the outcome of that report, thetopic of the fourth shall be decided. EFFICIENCY Efficiency is the mostimportant part of my research as yet.

    Since the object of my research is to findout which type of rockets are the most efficient and why, the reader of thispaper must have a basic understanding of efficiency. Once this is established,new definitions will come into play, all of these shall be crucial in theunderstanding of the paper. Terms Needed To Understand Efficiency G- a unit ofacceleration equal to 9. 8 meters/second/second (accelerating at a pace of 9. 8meters per second every second) Specific Impulse (Isp)- A measurement inseconds of efficiency. Properties of Efficiency Efficiency is the most accurateindicator of rockets performance.

    As stated in the aforementioned definitions,specific impulse is the basic unit of measurement of rocket efficiency. Isp isfound by dividing the exhaust velocity by g (definition also mentioned above). Since velocity is measured in m/s (meters per second) and each g is equal to 9. 8m/s/s (meters per second every second), the terms cancel to leave just a unit inseconds. The resulting figure, is the duration of time for which one kilogram ofpropellant can produce one kilogram of thrust. Thus, a higher number representsa better, and more efficient rocket.

    To give the reader an idea of the averageIsp of several type of rockets, I have listed some average figures forefficiency of certain types of rockets below. Average Efficiencies of CertainRockets Next, I have listed the Isp values for some basic types of rockets. After that I shall explain some of the most well known types of rockets. BasicRocket Types An RPS (rocket propulsion system) is a powerplant that pushes avehicle forward by ejecting matter that is stored within the vehicle. Thismatter is called propellant. The propellant is the most crucial part of moving avehicle through space.

    Their energy source, the vehicles they are used on, andthe type of propellant classify the specific types of systems. Liquid PropellantRockets All LPRs (Liquid Propelled Rockets) contain the same basic devices. Thenext paragraph shall discuss these functions and examine their purpose. Thefirst such device is the thrust chamber.

    The thrust chamber contains aninjector, a combustion chamber and a nozzle. The thrust chamber is the placewhere the propellants are injected, atomized, then mixed and finally burned toform reaction products in the form of gas. Next, the products are acceleratedand ejected at extremely high velocities to create thrust. The injector is aseries of pipes that allow the liquid propellant to move into the combustionchamber chamber to be made into thrust while atomizing and mixing them. Theexhaust nozzle is the last step in the releasing of thrust.

    It allows the hotgas to expand and then accelerates them to supersonic velocities. On somevehicles, the nozzle acts as a steering mechanism by placing it on an electronicaxis for which it can be turned by an automated steering wheel. There are twomajor types of feed systems used by LPRs; one uses pumps to move propellants tocombustion chambers; the other, uses high pressure to expel propellants fromtheir tanks. On most space vehicles the engines are mounted in pairs at theperimeter of the craft.

    Normally to opposite facing thrust chambers arecontrolled automatedly to turn the ship. Generally, a minimum of 12 thrustchambers is required for turning. Solid Propellant Rockets Solid PropellantRockets (SPRs) contains a huge number of types of engines. The propellant thatis to be burned is held in the combustion chamber.

    The propellant charge (grain)contains chemical elements for complete burning. When it is ignited, it burns onall its exposed sides. If the design of the grain is changed, then less can beexposed; the less exposed, the less fuel burned. The average burning rate isaround 1.

    8 cc per second. The rate normally depends on the propellantingredients. The more chamber pressure, the more propellant burnt. The way tomake an efficient SPR is to pack as much solid propellant into a chamber volumeas possible. Theoretically, it would be ideal to burn the propellant like acigar, from one end to the other.

    For this reason, scientists created anend-burning grain, which has proved extremely successful. Electric Rockets Thereare three types of electric propulsion systems (EPS); the three includeelectromagnetic, electrothermal and electrostatic. They are, in some ways more arocket of the future then one of the present, somewhat like the NERVA project(see next section). In the electrothermal system the propellant is heated orvaporized electric heaters. The hot gas is then expanded through a nozzle theway it is in a chemical rocket. In an electrostatic system, interactingelectrostatic fields and small charged particles such as colloidal particlesachieve acceleration.

    In an electromagnetic rocket, acceleration is achieved byplacing propellant plasma (a high temperature, electrically natural gas thatcontains electrons, ions and neutral molecular species) in an electromagneticfield thus causing a reaction that releases thrust. Nuclear Rockets Unlike theaforementioned rockets, nuclear rockets do not generate its power throughchemical combustion. The way its power is formed, is through nuclear fission. Itheats a propellant like hydrogen in a fission reactor and the explosion expelsthe propellant at amazing speeds, which exceed twice what any other rocket canproduce.

    Its efficiency rating is around 850, as compared to the 450 of the nextbest type, the cryogenic rocket. Unfortunately due to the extreme dangers ofnuclear fission inside a shuttle, the main project for researching the nuclearrockets, NERVA, was scrubbed. Most likely, in the future, scientists will devisea plan to minimize the risks, whereupon research will begin again. SECTION 3 AHistory INTRODUCTION The third section of this report shall begin by indicatingthe steps in which rocketry was created, as to allow the reader of this paper tobetter understand the way rockets work. It shall show the works of Tsiolkovsky,Goddard, Oberth and a few others.

    The report shall then end in a detailedconclusion. The conclusion will be based on the summary and discuss all that hasbeen written. It shall end in giving opinions as to the future uses of thespecific areas found in the research. Development of Modern Rocketry EARLYHISTORY In around 1232 AD, in China, rockets were created. During the war withthe Mongols, the Chinese would strap an early form of gunpowder to the shaft ofan arrow. This made them fly longer and faster than any of the regular arrowsthat the Mongols used.

    About ten years later, in Europe, another major discoverywas made. An Englishman, Robert Bacon, created a more practical formula forgunpowder. He did this by mixing 41. 2 parts saltpeter, 29. 4 parts charcoal and29. 4 parts sulfur.

    He was able to distill saltpeter, which produces oxygen, toallow the rocket to burn faster. In the 18th century, the British encounterencountered rocket warfare with India. The Indians probably learned the secretof rocket treat from Arab traders in the 17th century. The Indians, who were ledby Hyder Ali, gave thousands of men the task of throwing rockets. The rocketswere first thrown, then propelled itself. They attached an eight foot longbamboo stalk to six pound iron tube filled with fuse and powder.

    The rocketswere able to fly up to 1. 5 miles. Modern Discoveries Tsiolkovsky Tsiolkovsky, aRussian teacher, established that a rocket would work in the vacuum of space, in1883. In 1903, he wrote a book explaining how space travel was possible, usingliquid propelled rockets. He created drawings of possible space ships propelledby either liquid oxygen and liquid hydrogen or liquid oxygen and kerosene. Thesketches also show valves to transport the liquid propellant into a combustionchamber and showed how vanes could be created in the exhaust for steering.

    Healso illustrated the crew lying on their backs in a pressurized cabin in orderto withstand the pressure of such high speeds. Tsiolkovsky also thought ofrocket staging. Rocket staging is a series of rockets that fire one after theother. When one finishes and the other fires, the useless rocket is jettisoned. He thought this was the only way to put heavy objects such as satellites intospace. Goddard Although Tsiolkovsky thought up the ideas of advanced rocketry,still more had to be considered, and it had to become reality.

    The next pioneer,was the father of American rocketry, Robert Goddard. He first, created a bazookatype rocket. The bazooka was fairly large solid-propellant rocket. In 1919, hewrote a text called A Method of Reaching Extreme Altitudes. Two years later, hebagan to experiment with the liquid fuels that Tsiolkovsky.

    In 1926, Goddardfinally launched the first liquid propelled rocket. It was fueled by gasolineand liquid oxygen. It rose to a height of 41 feet and traveled at 60 miles perhour. It only traveled 56 meters but it set the foundation for the future ofrocketry. In May 1935, he released a rocket that featured gyro controlledexhaust vanes which pushed it to travel 1.

    5 miles above the ground at a totallyunprecedented 700 miles per hour. GERMAN ROCKET SCIENTISTS In 1923 a Germanrocket scientist Hermann Oberth published The Rocket Into Planetary Space. Hefavored liquid propellants, as Goddard, because of their power. Hisexperimentation inspired the creation of the Society for Space Travel. Thesociety passionately experimented with ways to improve the liquid propellantrocket. On February 21, 1931, a member of The Society for Space Travel, JohannesWinkler, launched the second liquid fuel rocket.

    Winklers rocket waspropelled by liquid methane and liquid oxygen. It failed totally, going a mereten feet forward. Three weeks later another rocket ascended to about 2000 feet. The entire Society for Space Travel began working on two rocket series, theMirak and Repulsor. The late model Repulsors could reach an altitude of 1 mile. When The Society for Space Travel ran out of money, they made a demonstration ofthe Repulsor for the German Army.

    A member, Werner Von Braun compiled somestatistics for the army who gave it to Hitler. They realized that this did notviolate the treaty which did not allow them to build airplanes. Hitler startedthe Army Weapons Department. Von Braun was placed in charge of rocketdevelopment. Within a few years Von Braun was experimenting with highlydeveloped rockets and was firing them in secret at the island of Birkum.

    In 1934he created two rockets, that could ascend to over 1. 5 miles. After that, TheSociety for Space Travel fell apart due to financial problems. In 1937, a rocketresearch station was constructed on the Baltic coast.

    Here the Germans createdsuch rockets as the famous V-1 Buzz Bombs, and the mammoth V-2 which were reallyrocket-powered flying bombs. Conclusion In this research, it has beendemonstrated how all rocket engines work. It illustrates how propellants aremoved into a combustion chamber, and expelled at extremely high speeds. It showsthe properties of efficiency, the basic measure by which all rockets arecompared. It shows how efficiency is measure by specific impulse, which iscalculated by the propellants exhaust velocity divided by g.

    It has given abasic comparison as to the efficiency of various rockets and has shown thereasons for being at their respective ranks. Also shown, is the pioneering ofrocketry starting in the mid 1200s. All this has shown the basic properties ofspace propulsion.Bibliography – the Rocket Engine Specifications pagefrom the Artemis Project ( ) Data Book Orbital Report News Agency’s Launch Vehicle database JPL’s Mission & Spacecraft Library Mark Wade’s “Encyclopedia Astronautica” The Space Shuttle Reference Manual -Solar electric propulsion on the Deep Space 1 probe “Rockets” Sutton, GeorgeP Groliers Online Encyclopedia

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