То 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 Challenge^

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 persistent^ current. The charged particles in the solar wind are

deflected^ 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 flux^, 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-

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-shielded^ 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.

А 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.

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