Word: km
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Dates: during 1990-1999
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...crossing the Caribbean? Strangely enough, one good place to be is Bangor, Me., a city thousands of kilometers north of the smugglers' favorite routes. Last week in Bangor the U.S. Air Force showed off the operations center for a new radar system that can "see" up to 3,300 km (2,000 miles), or nearly ten times as far as conventional radar. Built by General Electric, the OTH (for over-the- horizon) radar system was originally developed to give the U.S. military an early warning of any approaching Soviet bombers. But in these days of easing tensions between East...
...radar operates by sending out radio beams and listening for echoes as the signals bounce back from distant objects. The range of conventional radar is limited by the earth's curvature, since the signal must follow a straight line. Standard ground-based systems work for about 80 km (50 miles), and airborne equipment for 320 km (200 miles). OTH radar gets around the limit by sending beams up to the ionosphere, an atmospheric layer of charged atoms that begins some 75 km (46 miles) above the earth's surface. The signals are reflected by the ionosphere over the horizon, where...
...effective, the OTH radar system had to be huge. The signals are sent from three transmitting antennas, each more than 1,095 meters (3,600 ft.) long, in Moscow, Me. Some 175 km (110 miles) away, in Columbia Falls, are three receiving antennas, each stretching nearly 1,520 meters (5,000 ft.). The whole system is controlled by 28 of Digital Equipment Corp.'s powerful VAX computers located at the operations center in Bangor...
Battery-powered autos are clean, quiet and remarkably energy efficient -- but they have a huge problem. Once they get on the road, even the most advanced models can travel only 190 km (120 miles) or so before they run out of wattage, and then they need to be plugged into an outlet for about six hours to get fully recharged. Now the city of Los Angeles and a California power company have proposed a radical solution to the problem of powering electric cars: electrify the roads. Last week they announced a $2 million demonstration project in which electric cables will...
Clear-water relay. To raise consciousness about contamination in rivers and streams, activists will collect a bottle of springwater in Lincoln County, Ky., and relay it by canoe down the Green River's 616-km (382-mile) length to Evansville...