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| SCIENCE & TECHNOLOGY |
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Solar power from satellites Space shuttle to repair Hubble
THIS UNIVERSE |
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Solar power from satellites In recent years, solar power has emerged as one of the many alluring alternative energy sources to overcome the energy crunch triggered off by the skyrocketing of oil prices. Clearly and apparently, solar power is cheap, non-polluting and abundant source of energy. As pointed out by energy experts, in the years ahead as the stock of highly polluting fossil fuels keeps dwindling, the sun might hold the key to drive the engine of this “overrated and overcrowded planet”. But all said and done, at the present state of development, the cost of technology for harnessing solar power is still high in comparison to the market price of the conventional energy sources. Of course, rapid strides in technology could, in the long run, make solar power an economically viable and ecofriendly source of energy. In fact, an overwhelming proportion of current satellite missions derive their energy from solar cells embedded on their outer surface. For more than three and a half decades now, space scientists have been working on the idea of solar power satellite (SPS) to mitigate the energy crisis looming large over our planet. It was in 1968 that the American scientist Dr Peter Gloser mooted the interesting idea of developing a large array of solar power panels to be stationed into the geostationary orbit —36,000 km above the equator where a satellite appears stationary in relation to earth for all practical purposes — for tapping the abundant and freely available solar power and beaming it back to earth for its conversion into electricity. Meanwhile, in a development of significance, the California based Space Island Group Inc is planning to raise funds with a view to launching two SPS into orbit by 2012. As envisaged now, these two satellites will generate electricity using the solar power and transmit it to the earth in the form of microwaves. According to Pranav Mehta, India Director of Space Island Group, everything going as planned, the companies would sell power to India and China at 10 cents per kilowatt hour without a hike in price till 2030. As pointed out by Mehta the biggest plus point of placing a solar power generating system in space is the unobstructed view of the sun irrespective of brightness and darkness, and seasonal changes. while on earth, the efficiency of solar power system is around 20 per cent, in space it is around 50 per cent. Basically, the SPS concept envisages using the nearly constant availability of sunlight in space to generate electricity on earth. The energy would then be beamed from SPS to earth using either microwave or laser transmission systems. But then the biggest challenge involved in realising an SPS system is how to lift and deploy huge quantities of materials to assemble solar arrays half way up in space. As it is, installing an SPS involves ferrying hundreds of tonnes of materials into low earth orbit for assembling the satellite and pushing them into geostationary orbit subsequently. For deploying such a huge quantity of materials into space, one needs a huge liftoff space vehicle. and herein lies the major challenge of realising an SPS system. Significantly, the concept of SPS has evolved further to include such options as lunar-solar power where the solar energy stations could be located on the moon. This would obviously have the advantage of easing construction in addition to the fact that moon can serve as a very stable platform.On its part, India too has unveiled a proposal for an SPS, though at the moment it is in a very rudimentary conceptual stage. According to Raghavan Gopalaswami, a former chief of the Hyderabard-based defence outfit Bharat Dynamics Ltd, the intensity of sunlight in outer space is much higher than on earth. Americans, Russians and Europeans all are active in developing the technology of SPS and pave the way for the realisation of technologically advanced and economically efficient space based solar power generation system with a view to finding a solution to the energy crunch haunting the humankind. |
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Space shuttle to repair Hubble NASA will send a space shuttle and seven astronauts to repair and upgrade the Hubble Space Telescope as early as May 2008, overturning an earlier decision that the complex mission posed too much of a risk. NASA Administrator Michael Griffin announced Tuesday that his 18-month review had concluded that the mission could be safely accomplished. Speaking at the Goddard Space Flight Center in Greenbelt, Md., home to much of the Hubble workforce, his words were met with an explosion of joy. “I really wanted us to find a technical way — not a fantasy way — to where we could say we could repair Hubble,” Griffin said. “We concluded we could do it within budget and without jeopardising the safety of the astronauts.” The 11-day mission — most likely on the space shuttle Discovery — is expected to keep the popular orbiting telescope operating for five more years by replacing worn gyroscopes and batteries. The astronauts will also install new instruments that will increase the telescope’s capacity to study even more distant galaxies and to explore the mysteries of dark energy, intergalactic gases, and the early expansion of the universe following the Big Bang. The announcement marked a turnaround from NASA’s widely criticised 2004 decision to cancel the last of four scheduled missions to service the Hubble. That decision was made in the aftermath of the February, 2003, Columbia space shuttle disaster, in which Indian-origin astronaut Kalpana Chawla was among those killed. Speaking at Goddard, Griffin said the three successful post-Columbia shuttle flights had convinced him that NASA now knows much better how to deal with any possible damage to the shuttle caused by the stresses of launch. Any damage, he said “could, should and ought to be repairable” in space. The shuttle team will need four or five space walks to complete its work, which is designed to allow the 16-year-old Hubble to continue sending back images at least until a replacement telescope is launched in 2013.
— LA Times-Washington Post |
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What is the reason for magnetic energy and gravitational force? This question cannot be answered simply or easily. It needs a fair amount of elaboration.Firstly let me clarify that magnetism and gravity belong to different classes of forces. I say this in spite of the fact that ultimately one might find a way of describing all forces through a single unified theory — we are not there yet. The four classes of forces that seem to describe and govern most of the universe and its phenomena are 1) Gravitation, 2) Electro-magnetism, 3) the Weak force and 4) the Strong force. Gravitation is the most familiar because things fall down when released from a height. This is also the force between any two masses merely because they have mass. It is found that gravitation also affects light or radiation. Gravity describes the planetary motions and dominates when large masses are involved. Theory of gravitation associated with the name of Newton has been modified and refined by the General Theory of Relativity, though in the ordinary world the Newtonian gravitation is a fairly good approximation and suffices. You have asked for the reason for the gravitational force. It is possible that the existence of mass might be fundamentally connected with this. In the study of astronomy and cosmology there are hints that some more fundamental particles might account for gravitation being what it is. So the simple answer to your question is that I do not quite know. You must, of course, realise that it is like asking why should there be a universe like ours — why the sun and the earth, the stars and galaxies, why life and people? These are hard questions to answer, you would agree. You could almost say that one of the possible universes was the one we have, but there might be others with which we have no connection and where we would certainly be non-existent. Coming now to what you call magnetic energy. Incidentally where there is force, energy is also implied because when force acts energy is changed. This comes from the very definition of these two terms. Magnetism and electricity were unified some time ago. They are very elegantly described by a single theory. Wherever there are electric currents they also have magnetic fields. Movement of a conductor through a magnetic field produces electric current. All this is fairly well understood and extensively utilised in our homes and industry in general.In this case also one might state that the why of electromagnetism is understood from basic principles and symmetries. The universe seems to have a character in which, according to the current understanding, electromagnetism, the weak force responsible for phenomena like radioactivity and the strong force that is responsible for structure and phenomena at the nuclear level have to be what they are, more or less. We still have some ways to travel to include gravitation in the world of this interdependence and inevitability. |
Ancient Indian spiritual literature is replete with fulsome hymns in praise of the sun as an indefatigable dynamo, lighting up the heavens with its indescribable splendour. Vedic texts also describe sun the remover of darkness and illness and a veritable provider of inexhaustible energy.