ИНОСТРАННЫЙ ЯЗЫК В ТЕХНИЧЕСКОМ УНИВЕРСИТЕТЕ (956018), страница 48

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To be read after Lesson 11

Space Cooling

A new method of cooling that can generate cryogenic tempera­tures of 200 °C below zero without the use of electricity and with almost no moving parts has been tested at the Jet Propulsion Labo­ratory in Pasadena, California. The refrigerator used for the pur­pose was recently tested to — 253 °C, only 20 degrees above absolute zero, the lowest possible temperature.

In space such cooling system could increase the life of future space station refuelling ports by cooling the large liquid-hydrogen fuel tanks which are likely to be in service.

In future earth applications it could be used for cooling hydro­gen-powered cars and planes, as well as for cooling superconduct­ing motors and computers.

According to the JPL (Jet Propulsion Laboratory) experts the key lies in the use of hydrides, materials that interact with hydro­gen. These materials absorb tremendous amounts of hydrogen gas at room temperature. The engineers of the JPL have taken advan­tage of this property to build a series of devices that act as compres­sors and provide a continuous cooling stream of liquid hydrogen.

The system saves weight in space since it can use direct solar heat instead of electricity from heavier, inefficient electric systems. Because it has so few moving parts and uses the same supply of gas in a closed cycle, it could operate for many decades. Because of its long potential lifetime, the system could be used to cool infrared sensors during missions to the other planets, which may take 10 years or more to complete.

The Propulsion Challenge¹

Magsails are a form of solar sails that use a completely different type of physical interaction with the Sun. Magsail is a simple loop (петля, контур) of high-temperature superconducting wire carry­ing a persistent² current. The charged particles in the solar wind are deflected³ by the magnetic field, producing thrust. Although the thrust density in the solar ion wind flux is 5,000 times less than the thrust density in the solar photon flux⁴, the mass of a solar sail goes directly with the area, whereas the mass of the magsail rises with the perimeter of the enclosed area.

The effective cross-sectional area of the magnetic field around the magsail is about a hundred times the physical area of the loop. As a result, preliminary calculations show the thrust-to-weight ra-

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tio of a magsail can be an order of magnitude (порядок величины) better than a solar sail. Recent thermal balance calculations indi­cate that a properly Sun-shielded⁵ cable can be passively main­tained at a temperature of 65 К in space, well below the supercon­ducting transition point for many of the new high temperature su­perconductors.

Notes to the Text

1. problem, difficulty, invitation to see which is better

2. continuing

3. cause to turn away from

4. flow

5. protected

Computer Graphics

Computer graphics are known to be pictures and drawings pro­duced by computers. A graphics program interprets the input pro­vided by the user and transports it into images that can be displayed on the screen, printed on paper or transferred to microfilm. In the process the computer uses hundreds of mathematical formulas to convert the bits of data into precise shapes and colours. Graphics can be developed for a variety of uses including illustrations, archi­tectural designs and detailed engineering drawings.

Mechanical engineering uses sophisticated programs for appli­cations in computer-aided design (CAD) and computer-aided manufacturing (CAM). In the car industry CAD software is used to develop, model and test car designs before the actual parts are made. This can save a lot of time and money.

Basically, computer graphics help users to understand complex information quickly by presenting it in more understandable and clearer visual forms. Electric engineers use computer graphics for designing circuits and in business it is possible to present informa­tion as graphics and diagrams. These are certain to be much more effective ways of communicating than lists of figures or long expla­nations.

Today, three-dimensional graphics along with colour and com­puter animation are supposed to be essential for graphic design, computer-aided engineering (CAE) and academic research. Com­puter animation is the process of creating objects and pictures which move across the screen; it is used by scientists and engineers to analyze problems. With appropriate software they can study the structure of objects and how it is affected by particular changes.

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A graphic package is the software that enables the user to draw and manipulate objects on a computer. Each graphic package has its own facilities, as well as a wide range of basic drawing and paint­ing tools. The collection of tools in a package is known as a palette. The basic geometric shapes, such as lines between two points, arcs, circles, polygons, ellipses and even text, making graphical objects are called «primitives». You can choose both the primitive you want and where it should go on the screen. Moreover, you can specify the «attributes» of each primitive, e.g., its colour, line type and so on. The various tools in a palette usually appear together as pop-up icons in a menu. To use one you can activate it by clicking on it.

After specifying the primitives and their attributes you must transform them. Transformation means moving or manipulating the object by translating, rotating and scaling the object.

Translation is moving an object along an axis to somewhere else in the viewing area. Rotation is turning the object larger or smaller in any of the horizontal, vertical or depth direction (corresponding to the x, у and z axis). The term «rendering» describes the tech­niques used to make your object look real. Rendering includes hid­den surface removal, light sources and reflections.

To be read after Lesson 12

The Space Age

Russia was the first nation into space and is recognized as the world's leader in building space stations and conducting long-duration space missions. Since Yury Gagarin's epic flight Russian space science and engineering have come a long way. Space tech­nology remains Russia's deepest source of pride (гордость). Russia has launched a great number of space vehicles designed to perform a variety of functions. Unmanned satellites have been of great sig­nificance in the exploration and peaceful use of outer space. They help us learn more about the relations between processes occurring on the sun and near the earth and study the structure of the upper atmosphere. These satellites are provided with scientific equipment for space navigation of civil aviation and ships, as well as explora­tion of the World Ocean, the earth's surface and its natural re­sources.

In April 1971, history's first space station, Salyut 1, was launched and over the next 15 years six its subsequent versions op­erated in space. Many orbital manned flights were performed

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aboard these stations involving a lot of cosmonauts, most of them having flown several times. Russian cosmonauts are known to hold the record for the longest time in space (L. Kizim has worked 375 days) and for continuous stay in space (V. Titov and M. Manarov — 365 days, i.e. a year). The knowledge of Russian doctors and re­searchers about the medical and psychological consequences of longterm space flight far exceed that of American scientists. In 1973, two years after Salyut 1, the United States launched Skylab, the Western World's first space station which was used for three highly successful missions. All these manned missions paved the way for even longer stays aboard the Russian Mir space station and, then, aboard the International Space Station.

The most successful Mir space station was launched in Febru­ary 1986. It was expected to have a lifetime of only five years but it had been in orbit for 15 years before its controlled re-entry into the atmosphere. This space station was equipped with an astronomical observatory module named Kwant. It incorporated all the novelty that could be offered by designers and engineers. To keep produc­tivity high, Russian designers paid much attention to the space sta­tion livability. The interior of Mir was painted in two colours to provide the crew with a sense of floor and ceiling. On Mir cosmo­nauts got two days off each week and had a special radio so that they could talk to their families and with any sportsman, scientist or celebrity they wanted.

With the twin Vega space probes being successfully launched in 1986, Russian scientists conducted close-range studies of Halley's comet and gathered impressive scientific data about Venus. Vega 1 and Vega 2 carrying more than 30 research instruments passed within 10,000 kilometers of the comet's heart, transmitted high-quality pictures to Earth and revealed for the first time the dimen­sions and dynamics of its ten-mile-long nucleus. The relative speed of approaching the comet was equal to 78 km/sec. It should be pointed out that the study of Halley's comet was conducted on the basis of extensive cooperation of scientists. Scientists from nine countries, including the U.S, joined the Vega project.

When the 170-million horse power launch vehicle called «Energia» was successfully tested in 1987, Russia has gone far ahead of the United States in the space race. With the new multi-purpose Energia rocket it became possible to put into orbit a 100-ton payload (one must know that the first satellite carried 83,6 kg).

The first International Space Station components, Zarya and Unity, have opened a new era of space exploration. The three-stage

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Russian Proton booster was used to launch the Zarya module. The rocket was designed by the Salyut Design Bureau and is manufac­tured by the Khrunichev State Research and Production Space Centre in Moscow. The Proton is among the most reliable heavy-lift launch vehicles in operation with its reliability rating about 98 per cent. Proton measures about 180 feet tall, 24 feet in diameter at its widest point and weighs about 1,540,000 pounds when fully fueled for launch. The engines use nitrogen tetroxide, an oxidizer, and dimethyl hydrazine, a fuel, as propellants. The first stage includes six engines providing about 1.9 million pounds of thrust at launch. Four engines creating 475,000 pounds of thrust power the Proton's second stage. The Proton's third and final stage is powered by a single engine that creates 125,000 pounds of thrust.

Assembling the station will be unprecedented task, turning the Earth orbit into a constantly-changing construction site. More than 100 elements will be joined over the course of 45 assembly flights using the Space Shuttle and two types of Russian rockets. An international team of astronauts and cosmonauts will do much of the work by hand, performing more space works in just five years than have been conducted throughout the history of space flight. They will be assisted by a new generation of robotic arms, hands and perhaps even free-flying robotic «eyes».

The international partners, Canada, Japan, the European Space Agency, are supposed to contribute the following key ele­ments to the ISS: Canada is to provide a robotic arm to be used for assembly and maintenance tasks on the station. The European Space Agency is building a pressurized laboratory to be launched on the Space Shuttle. Japan is building a laboratory module with an attached platform where experiments can be exposed to space as well as logistics transport vehicles.

Scientists believe the ISS to be the most advanced base for de­veloping technologies, systems and procedures to enable safe, effi­cient and permanent human presence in space.

Cryptography

From e-mail to cellular communications, from secure Web ac­cess to digital money, cryptography is an essential part of today's information systems. The only way to protect a message is to en­code it with some form of encryption. Data encryption is very im­portant for network security, particularly when sending confidential information. Encryption is the process of encoding data so that un­authorized users can't read it. Decryption is the process of decod-

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ing encrypted data transmitted to you. The most common methods of protection are passwords for access control, encryption and de­cryption systems, and firewalls. Firewall is a software and hardware device that allows limited access to an internal network from the Internet.

Cryptography helps provide accuracy and confidentiality. It can prove your identity or protect your anonymity. It can prevent vandals from changing your Web page and industrial competitors from reading your confidential documents. And in the future, as commerce and communications continue to move to computer networks, cryptography will become more and more vital.

But the cryptography now on the market does not provide the level of security it advertised. Most systems are not designed and implemented together with cryptographers. Present-day computer security is a house of cards; it may stand for now, but it can't last. Electronic vandalism is an increasingly serious problem. Computer vandals take advantage of technologies newer than the system they attack, using techniques the designers never thought of and even invent new mathematics to attack the system with.

No one can guarantee 100 % security. But we can work toward 100 % risk acceptance. Fraud (обман) exists in current commerce systems. Yet these systems are still successful, because the benefits and conveniences are greater than the losses. Some systems are not perfect, but they are often good enough. A good cryptographic sys­tem provides a balance between what possible and what is acceptable.

The good news about cryptography is that we already have the algorithms and protocols we need to secure our systems. The bad news is that that was the easy part; implementing the protocols suc­cessfully requires considerable expertise. Thus, there is an enor­mous difference between a mathematic algorithm and its concrete implementation in hardware and software.

Design work is the main support of the science of cryptography and it is very specialized. Cryptography combines several areas of mathematics: number theory, complexity theory, information the­ory, probability theory, abstract algebra, and formal analysis, among others. Unfortunately, few can do the science properly, and a little knowledge is a dangerous thing: inexperienced cryptogra­phers almost always design imperfect systems. Quality systems use published and well-understood algorithms and protocols. Besides, only when cryptography is designed with careful consideration of users' needs and then integrated, can it protect their systems, re­sources, and data.

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