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 (, ) 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-
tio of a magsail can be an order of magnitude ( ) 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 in space, well below the superconducting transition point for many of the new high temperature superconductors.
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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.
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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.
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, 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.
