Space Propulsion

Space Propulsion The following is a research project on Space Vehicle Propulsion. It shall consist of four sections, each discussing specific topics. Section One lays out the basic ideas of rocketry. Section Two compares Rocket Propulsion Systems, and shows the basis for the comparison. It also shows how each specific Rocket System works and Section Three gives a description of how Space Propulsion has evolved and contains a conclusion. SECTION 1 The Basics Section One is a brief description of the basic properties of Rocket Systems.

It defines the key terms and shows how a basic rocket works. It also shows the State if The Art. I have chosen to do my project on space vehicle propulsion. Basically, this means that my research shall be based primarily on rocketry. Rocketry is a way of propulsion that has developed in numerous ways since it was first used to propel fireworks in the 16th century.

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It has emerged into an extremely complicated science that few actually understand. Most space rocketry in America is used in NASA (National Aeronautics and Space Association) space projects. NASA, a government association that focuses on space exploration, is the main user of rocket technology. It is used mostly to power their satellites and shuttles into space. Pushing an object that weighs as much as a space shuttle does directly vertical until escaping the Earths atmosphere requires a tremendous amount of power. This is why NASA uses rockets.

Rockets are essentially the most powerful forms of propulsion there is today. Space Vehicle Propulsion is based rocket engines. The basic principle of rocket engine is that when fuel is burned in the engine, the reaction mass is expelled at high speeds. As a result of Newtons law of action and reaction this pushes the vehicle in the opposite direction of the one in which the reaction mass is moving. Thrust is the force that the engine 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 is measured by the time it takes for one kilogram of propellant to create one kilogram of thrust. The goal of my research is to find out what makes these engines more efficient. In rocketry, the state of the art is extremely hard to define, since there are so many different forms of rocketry ranging from liquid propellant rockets to fireworks. The state of the art though is probably nuclear powered rockets. It is much more efficient because it does not use chemical combustion like most rockets do. Instead NFRRs (Nuclear Fission Reactor Rockets) heat hydrogen in a fission reactor which expels the propellant at blistering speeds.

Much research is being done with NFRRs. They are still highly experimental because of the dangers that could be associated with them. The NERVA (Nuclear Engine for Rocket Vehicle Application) was one of the most extensive NFRR research projects, however it failed because of the inability figure out an approach to putting the research into a developmental stage. SECTION 2 Specific Rocket Propulsion Systems Section One has laid the foundation for further research in the are of rocketry. Section two shall discuss properties of efficiency in more depth, it shall lay out the types of rockets in existence 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 these specific rockets efficiency and depending on the outcome of that report, the topic of the fourth shall be decided. EFFICIENCY Efficiency is the most important part of my research as yet. Since the object of my research is to find out which type of rockets are the most efficient and why, the reader of this paper must have a basic understanding of efficiency. Once this is established, new definitions will come into play, all of these shall be crucial in the understanding of the paper. Terms Needed To Understand Efficiency G- a unit of acceleration [equal to 9.8 meters/second/second (accelerating at a pace of 9.8 meters per second every second)] Specific Impulse (Isp)- A measurement in seconds of efficiency. Properties of Efficiency Efficiency is the most accurate indicator of rockets performance.

As stated in the aforementioned definitions, specific impulse is the basic unit of measurement of rocket efficiency. Isp is found 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 9.8 m/s/s (meters per second every second), the terms cancel to leave just a unit in seconds. The resulting figure, is the duration of time for which one kilogram of propellant can produce one kilogram of thrust. Thus, a higher number represents a better, and more efficient rocket.

To give the reader an idea of the average Isp of several type of rockets, I have listed some average figures for efficiency of certain types of rockets below. Average Efficiencies of Certain Rockets 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. Basic Rocket Types An RPS (rocket propulsion system) is a powerplant that pushes a vehicle forward by ejecting matter that is stored within the vehicle. This matter is called propellant.

The propellant is the most crucial part of moving a vehicle through space. Their energy source, the vehicles they are used on, and the type of propellant classify the specific types of systems. Liquid Propellant Rockets All LPRs (Liquid Propelled Rockets) contain the same basic devices. The next paragraph shall discuss these functions and examine their purpose. The first such device is the thrust chamber.

The thrust chamber contains an injector, a combustion chamber and a nozzle. The thrust chamber is the place where the propellants are injected, atomized, then mixed and finally burned to form reaction products in the form of gas. Next, the products are accelerated and ejected at extremely high velocities to create thrust. The injector is a series of pipes that allow the liquid propellant to move into the combustion chamber chamber to be made into thrust while atomizing and mixing them. The exhaust nozzle is the last step in the releasing of thrust. It allows the hot gas to expand and then accelerates them to supersonic velocities.

On some vehicles, the nozzle acts as a steering mechanism by placing it on an electronic axis for which it can be turned by an automated steering wheel. There are two major types of feed systems used by LPRs; one uses pumps to move propellants to combustion chambers; the other, uses high pressure to expel propellants from their tanks. On most space vehicles the engines are mounted in pairs at the perimeter of the craft. Normally to opposite facing thrust chambers are controlled automatedly to turn the ship. Generally, a minimum of 12 thrust chambers is required for turning. Solid Propellant Rockets Solid Propellant Rockets (SPRs) contains a huge number of types of engines. The propellant that is 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 on all its exposed sides. If the design of the grain is changed, then less can be exposed; the less exposed, the less fuel burned. The average burning rate is around 1.8 cc per second. The rate normally depends on the propellant ingredients. The more chamber pressure, the more propellant burnt. The way to make an efficient SPR is to pack as much solid propellant into a chamber volume as possible.

Theoretically, it would be ideal to burn the propellant like a cigar, from one end to the other. For this reason, scientists created an end-burning grain, which has proved extremely successful. Electric Rockets There are three types of electric propulsion systems (EPS); the three include e …