Satellites in space

Jeremy Curtis is an engineer and business development manager for space science at the Rutherford Appleton laboratory (RAL) in Oxfordshire. His job includes on the joint European telescope for X-ray astronomy (JET-X), due to have been launched in 1999 on the Russian Spectrum-X spacecraft. He says â€Å"I trained as a mechanical engineer, but I find space engineering exciting because I have to work with all kinds of experts such as astronomers, physicists, designers, programmers and technicians working around the world†. He was sponsored by RAL during his university degree and then spent several years on designs for a large proton synchrotron (a machine for accelerating protons to very high energies) before moving over to space instrument design. In the following passage he describes some of the aspects of space engineering. Why satellites? Getting spacecraft into orbit is a very expensive activity with typical launch costs generally measures in tens of thousands per kilogram. So what makes it worth the bother? There are three key reasons. First, a satellite is a good vantage point for studying the earth's surface and atmosphere – just think how many aircrafts would be needed to photograph the whole of the earth, or how many ships to monitor the temperature of the oceans. Second, if we want to study most of the radiation coming for distant parts of the universe we have to get above the atmosphere. The earth's atmosphere absorbs almost everything that tries to go through it – from X-rays to ultraviolet and from infrared to millimetre waves. Only visible light and radio waves can get through it. In fact, even visible light suffers – convection in the earth's atmosphere makes stars seem to jump about or twinkle, blurring telescope images, so a telescope in space produces sharper images than possible from earth. Finally, and not least, a communications satellite can beam TV pictures across the globe and link telephone users from different continents. The problem with space Once you've got through the huge trouble of expense of launching your satellite, a new set of problems confront you in space. First, a typical spacecraft may need several kilowatts of power – but where do you plug in? The only convenient renewable source of power is the sun, so most spacecrafts are equipped with panels of solar cells. You can see these on the Infrared space observatory (ISO). Unlike earth there is no worry about what to do on cloudy days, but batteries are still needed for periods when the satellite is in the earth's shadow (usually up to an hour or two per orbit) and the satellite has to be continually steered to keep the panels pointing at the sun. So now we have our spacecraft floating in orbit and pointing to face the sun all the time. Although the solar cells provide partial shade from sunlight the surface still starts to heat up, and with no air to convect the heat away the temperature can rise dramatically. To add to the difficulties, the other side of the spacecraft faces cold space (at about 3k or -270à ¯Ã‚ ¿Ã‚ ½C) and so begins to cool down, unchecked; this would distort the structure, wreck the electronics and decompose the materials that make up the spacecraft. So most surfaces of the spacecraft are covered in â€Å"space blanket† – multilayer insulation made of metallised plastic which reflects the radiation away and insulates the spacecraft. This is crinkly shiny material. 1.2 Studying with satellites The UoSAT satellites are very small, relatively low-cost, spacecraft whose purpose is to test and evaluate new systems and space technology and to enable students and amateur scientists to study the near-earth environment. They are designed and built by the university of Surrey spacecraft engineering research unit. UoSAT, also known as Oscar 11 has sensors to record the local magnetic field, providing information about solar and geomagnetic disturbances and there affects on radio communications at various frequencies. Instruments on board also measure some 60 items relating to the satellites operation. These include; the temperature of its faces, its batteries and other electronic devices; the current provided by its solar arrays; and the battery voltages. It can also receive store and transmit messages to simple radio receivers anywhere in the world. UoSAT's orbit takes it over both poles at a height of about 650km above the earth's surface, and the spinning of the earth allows it to receive data about six times a day. Each UoSAT spacecraft is designed to last about 7 years. Even small spacecrafts such as these need electricity to run all onboard systems, form the computer that controls it all, to the radio transmitters and receivers that send and receive all data to and from ground stations on the earths surface. UoSAT's are small, each with a mass of typically 50kg and about 0.5m across. For comparison, JET-X is about 540kg in mass and about 4.5m long. Communications satellites are larger still, with masses of typically 2 to 5 tonnes. At the top en of the scale is the proposed International Space Station (ISS) – a co-operative venture between 13 nations, including the UK. Construction and testing started in1995 and completion is due in 2002. The completed station will have a mass of about 470 tonnes, measure 110m from tip to tip of its solar arrays, and have pressured living and working space for its crew of six almost equal to the passenger space on two 747 jet airliners. It will have a demand of about 110kw. 1.3 Spacecraft power systems Schematic diagram of a spacecraft power system The below figure shows three main elements in a spacecraft power system. The primary source involves the use of fuel to produce electrical power. Primary sources include fuel cells in which a chemical reaction between hydrogen and oxygen produces electricity (with drinking water as a useful by-product), and radioisotope thermoelectric generators (RTG's) in which a radioactive decay process produces heating in a thermoelectric module that generates electricity. In spacecraft, the most common primary source s the photovoltaic cell, powered by solar radiation; here the initial fuel is protons in the sun, which undergo nuclear fusion. The secondary source is the energy storage system – usually a set of batteries. Sometimes regenerative fuel cells are used in which power from solar arrays electrolyses water to produce hydrogen and oxygen gases during the â€Å"charge† cycle, followed by hydrogen and oxygen recombining to make water during the â€Å"discharge† cycle. n electronic power control and distribution unit controls and adjusts the voltage and current inputs and outputs, often using primary and secondary sources together to boost the overall output power. There are other systems available and these are shown in figure 8 in the textbook, on page 69. Here are some listed: * Chemically fuelled turbines and reciprocating engines. * Chemical turbines and batteries. * Batteries. * Cryogenic hydrogen/oxygen expansion engines. * Cryogenic engines and fuel cells. * Fuel cells. * Nuclear dynamic systems. * Solar and nuclear dynamic systems. * Photovoltaic and radioisotope thermoelectric systems. A useful link to research this further is http://spacelink.msfc.nasa.gov/ Question 1, Page 70 Using figure 8 on page 69, decide which would be the most suitable power source(s) for a spacecraft needing; (a) 1kw power output for just one week. Cryogenic engines and fuel cells. (b) 10kw for 10 years. Solar and nuclear dynamic systems. The most common primary source of energy used in satellites is the photovoltaic cell or solar cell. Hundreds of thousands of such cells are connected together to make up solar arrays. UoSAT 2 and the ISS have many arrays of solar arrays attached to them. Solar cells have one important characteristic; they only generate electricity when illuminated. Orbiting satellites undergo between 90 and 5500 eclipses, moving into the shadow of the earth, each year. The former is typical of a geostationary telecommunications satellite, the latter of a satellite is in a low orbit like UoSAT 2. The ISS will have sixteen thirty minute periods of shadow each day. The secondary power supply is therefore vital, because during eclipse electrical power has to be supplied by batteries. There are also occasions when batteries are needed to provide power in addition to that of the solar panels. The spacecraft's solar panels are used to recharge its batteries when it emerges into sunlight. To do this they must provide a high enough voltage – higher than the batteries own voltage. (A charger for a 12v car battery provides about 30v.) The power system must therefore be carefully designed to ensure that the solar panels can charge the batteries and that the batteries can operate the electrical equipment on-board. So what voltage does a solar cell provide? How does this voltage vary with the brightness of the light? How can we connect up solar cells in order to charge batteries and operate equipment? These are questions I will explore in part two of this unit.

Data analysis Essay Example | Topics and Well Written Essays - 1250 words

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The Level of Service Inventory-Revised in Corrections Research Paper

The Level of Service Inventory-Revised in Corrections - Research Paper Example Using this tool, the government and other officials reduce cases of recidivism of certain offences in the society. In addition, through this tool various corrective institutions devise appropriate corrective measures and treatment practices for their inmates. LSI-R is a validated and recognized risk assessment tool that is highly efficient in identifying problem areas in various offenders’ lives. As a result, this tool helps reduce offender’s risk of recidivism. This quantitative survey tool offers offenders’ attributes and problems that are efficient in making vital decisions about relevant supervision and treatment method to be adopted. Furthermore, this instrument is useful in the allocation of various resources that are valid in solving the identified problems. Moreover, The Level of Service Inventory-Revised is a 54-item instrument, which is crucial and useful in assessing offenders across a range of 10 domains (Holsinger, Lowenkamp and Latessa 331). These areas are known to be closely related. This tool involves corrective measure such as prisons rehabilitative intervention that is useful in reducing the probability of offender ever engaging in crime. This practice is not complete without trained assessors. The se assessors examine offenders through interviews and validate the information and data collected through relevant external sources. The overall score from the structured interview and research is then used actuarially to associate the likelihood of reoccurrence of a behavior (Flores et al. 534). The last domain score is the most important since it is used to identify the most promising corrective measure for offenders to reduce and totally eliminate any chances of reoccurrence of a behavior. Due to its efficiency in assessing and predicting the probability of future reoccurrence of behavior, this tool is useful in

Walmart strategy in China Research Paper Example | Topics and Well Written Essays - 250 words

Walmart strategy in China - Research Paper Example These include cost controls, aiming at neglected niche, employees, suppliers, and distribution system among others (St-Maurice, Claudia, and Hsinhsin, 2008). In reference to Mr. Chan an economist in China, a greater number of businesses emphasis on fresh foods selection, thus visit a Walmart at most twice a day. He also argues that an upscale retailer in the country contrasts with the budget conscious reflection, thus developing at an exceptionally high rate. This is the strategy behind its success in USA (St-Maurice, Claudia, and Hsinhsin, 2008). On the other hand, Caffefour refers to international hyper chains located in Courcouronnes. This is in France. They are the largest hypermarkets in the world. The structure of these stores favors areas with high population than Walmart markets. This is an evident that China will suit the Carrefour strategy. In reference to the SWOT analysis, factors favoring the prosperity of Caffefour companies are more than those favoring Walmart. In reference to China’s politics, there is a sustainable environment, meaning that threats are minimal. However, the two strategies have different strengths, weaknesses, and opportunities. China being the nation with the highest population favors hypermarket as consumers will get attendance under one roof (St-Maurice, Claudia, and Hsinhsin,

Computer-Based Crimes Research Paper Example | Topics and Well Written Essays - 1000 words

Computer-Based Crimes - Research Paper Example In this case, monetary reward is the goal of hacking. Some hackers may also hack into a computer system with the aim of revenging. Such a hacker may steal and distribute sensitive information that could hurt the business. During a hacking episode, a hacker may connect to a target computer through an open network. For instance, open wireless connection offers hackers a quick way of attacking a computer system. Hackers can also use exploits to compromise a host and use it to gain access into the target computer. Once the hacker compromises the computer, they are may steal unprotected information from the computers. Phishing Computer-based crimes may also entail wrongful acquisition of data and information about users for the purpose of misrepresentation. Users who have access to computer systems have various identities, which describe the users such s they address or bank details. There are times when criminal attempt to acquire date from users by false means. For instance, criminals c ould dupe users into providing their bank details to a website that appears to be genuine, but not (Onescu, Irea, & Blajan, 2011). With a successful phishing, the criminal may use the data from the user to commit crime or for financial gain such as purchasing items online. Among the many computer-based crimes, phishing has the highest number of occurrences. There are various ways of phishing users online. One common technique is the use of an email that may appear to be from legitimate from a legitimate source. Using such emails, the sender will convince the user to follow a link and perhaps fill some sensitive information into a form and upon clicking the submit button send the information to the user. A typical scenario will be a criminal sending an... This research paper not only describes most common ways that criminals use to steal your data or hack computer system, but also provides recommendations on how to prevent such events and to increase user awareness of computer-related systems. Over year, the number of computer-based crimes has been rising and there are no signs the pattern will change, at least for now. Computer crime refers to any criminal activity where criminals target a computer, or use computers to violate the law. In recent years, criminals have used computers to commit crime such as stealing credit cards from unsuspecting users. With the number of computer crimes growing, there is significant interest on how users can enhance their safety when using computers. This essay describes many issues, that could affect the computer industry with computer-based crime and ethical issues being the chief. Using computers, criminals can commit crimes such as phishing where they capture sensitive user data and possibly misus e them. However, increasing user awareness and using antivirus software can help prevent and mitigate this threat. The researcher states that organizations can implement decision to curb ethical issues such as software piracy where employees copy and install software without purchasing them. Being that those firms deprives software vendors of revenues, purchasing the software and creating awareness is a fair strategy of reducing the practice. This solution align with fairness approach because it allows the developers to earn money while making software firms pay for tools they use to earn money.

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Philosophy of Education - Assignment Example Personally, I consider teaching as a platform where the pupil’s future will be greatly shaped by the kind of teachings they receive from me. Concerning the teachings offered at kindergarten, the approach is rather different in comparison to other levels. Normally, it does not just entail a curriculum that is easy to understand. Rather, the first days are usually vital for every kindergarten student because it is here that a relationship between the teacher and the pupils need to be established. That means the teacher has to understand the personalities and backgrounds of the pupils. Once this is done, the children need to be made lively always, if possible, in order to make the learning atmosphere easier. Upon exciting the learners, the education for pupils at this level starts with making them understand the alphabets. That is to say, training them how to pronounce correctly as well pointing out the ones that have a variance in terms of sound. Unlike in other teaching levels, this one has to be with minimal strictness, and is brief. My beliefs concerning teaching have to do with using this career to impart children with the right kind of teachings. In short, teaching is not a career as such, but rather a calling-like pursuit meant to bring a positive change. Because of strongly believing in this way, I often find myself going beyond the expectations. Besides teaching what is only listed, encouraging discipline, socialization among the children and thinking critically is often done in the class. Due to this approach, I normally set a goal for myself as well as that of pupils where I help students to achieve it even as I commit myself to doing so. Earlier, it was stated that a teacher is more than an employee; a role model is what every teacher is. Therefore, the goals I set are not just for the students but mine as well. Concerning the

Jones Soda Essay Example | Topics and Well Written Essays - 500 words - 1

Jones Soda - Essay Example These two companies are actually selling their brands and have already expanded globally through their manufacturing and expansion strategies. Compared with Jones Soda, Coke and Pepsi have gained remarkable market share in the worldwide market for beverages. What these two companies are trying to enhance as of the moment is in line with preventing customer erosion. In this regard, they always would want to emphasize the uniqueness of their taste and so consumers would always differentiate them from another product brands. Although Jones Soda is not that far from this strategy, but eventually its entire entry into the market together with its highly differentiated products are a bit experimental in their forms. In modern times, websites are the most convenient means to reach potential customers. In the case of Jones Soda, its website could actually serve substantial contribution to its operation. For instance, in its website consumers could freely address their concerns with Jones and its product offerings. Consumers for instance could actually suggest for product development, cross their voices over to Jones especially regarding matters about customer service, retailing and distribution, and many others. At the end of the day, the information gathered from the customers via Jones’ websites and if assessed, could pave the way for its competitive advantage in the future. Product differentiation strategy of Jones is something different from its industry. Jones Soda having at some point weird tastes for its soft drinks that some consumers appreciate is a remarkable advantage. The major benefit of this strategy is the opportunity for recognition of Jones Soda as another brand and key players in the soft drinks manufacturing industry. However, at some point, this differentiation may substantially lack focus especially in acceptability of the product in certain situations or occasions,