Text 16 b From Radio Valves to Cosmic Communications

Scan the text and find the answers to the following questions:

1. What is a major trend in modern radio electronics?

2. What possibilities does molecular electronics open up?

1. The reduction of radio instruments to miniature proportions and even smaller — is a major trend in modern radio electronics. The significance of this research has grown especially in connection with space research. It is impossible to equip a rocket for flights to other worlds without light, small and economical electronic apparatuses. The space rockets will carry a large amount of miniature equipment, systems for contact with the Earth, radars, computers for calculating flight trajectories, life-support systems, etc.

2. Bulky electronic equipment will have no place in the future. It will be unsuitable for automation of production, transport or domestic use.

3. Semiconductors and printed circuits have helped to reduce the size of apparatus considerably. The semiconducting instruments which have replaced electronic valves are much smaller and lighter, consume less power, are reliable and more durable.

The development of micromodules — tiny ceramic plates with a metallized coating has opened up big possibilities for making miniature electronic instruments. Semiconductors compressed into this plate are hundreds of times smaller than electronic valves. A radio receiver assembled of micromodules does not weigh more than 50 grammes.

4. Molecular electronics opens up new possibilities. The crystalline lattice can be changed by tantalum or titanium being added to semiconductors to obtain crystals with the required electrical properties.

At present, a radio-receiving set is assembled of separate, ordinary-size parts. The radio sets based on semiconductors or micromodules are also assembled of separate parts but tens and hundreds of times as small. The germanium or silicon plates will not operate like separate resistors or condensers, but as complete circuits — as generators or amplifiers.

5. All this might sound fantastic, but a scientist is looking still further ahead. Present research programmes are taking the development of even more miniature parts. We can say that when superminiature elements are developed, it will become possible to place approximately 200 million of these "parts" within one cubic centimetre. The density is approximately that of the human brain.

6. Cybernetics machines assembled of these units will memorize tremendous volumes of information and will give man invaluable assistance in diverse fields of life.

I Say where the reduction of radio instruments is especially significant.

II Find the information about semiconductor instruments.

III Think of the most suitable title for paragraph 3 out of the given ones:

1. Miniaturization.

2. Semiconductor Devices — a Big Step in the Direction of Miniaturization.

3. Steps of Miniaturization.

IV Give reasons for the development of micromodules.

V Say what new possibilities molecular electronics opens up.

VI Which paragraph contains the information directly connected with the title of the text.

TEXT 16 C

Application of electric-propulsion system

Translate the text using a dictionary:

An electrically powered spacecraft will probably be used for a round trip to some distant planet. A comparison between an electric and a conventional system for a proposed trip to Mars will show definite advantages of an electric system. For an eight-man crew to go on a 500-day trip to Mars, the weight of the electric and conventional system would be 450,000 and 8,000,000 pounds respectively. Both systems would have to be assembled in an Earth orbit. It would, however, take only two boosters to lift the material for the electric system while forty boosters would be needed for the conventional one. Electric power propulsion and all other needs would be generated by a nuclear-fission turbo-electric system.

There is, however, one problem that has not yet been discussed - the radiator equipment. Vapour exhausted from the turbine must be cooled and condensed before it returns to heat exchanger and the cycle is repeated. The cooling is accomplished with a radiator. This creates a weight problem, since a great deal of surface area is required for efficient heat exchange. Besides, to make the electric system practical, a large number of engines would be required because present designs are for engines generating only a small amount of thrust.

Much research has been conducted on electric propulsion systems as they can produce such low thrusts and can run for long periods. This means a high degree of reliability will have to be attained for such systems. Even with the large amount of research already accomplished, the electric system is still in a stage of development. Lighter and more powerful units must be developed if we want such systems to fulfil the promise they offer for interplanetary travel.