This Thyssen Krupp limestone stacking and reclaiming system can pile up as much as 7,500 metric tons of material per hour.

Krupp Fordertechnik GmbH's bulk materials handling unit in St. Ingbert-Rohrbach, Germany, filled the bill by constructing a circular limestone stacking and reclaiming system about 125 meters in diameter, with a capacity of approximately 90,000 cubic meters. The core bulk handling components are produced partly in Germany and partly by Indonesian manufacturers. The stacking system arrived in February and will begin operating when the plant is commissioned in the near future.

The entire stockpile is housed with-in a domed structure. Limestone is conveyed from the middle of the stockpile to the system's stacker. The stacker is equipped with a manually operated, 35-meter-long boom that piles limestone in a circle up to a height of 23.20 meters. The stacker, with a 2.2-meter-wide conveyor running at 2.1 meters per second, can stack 5,000 metric tons of limestone per hour.

The Krupp engineers installed a bridge-type scraper to reclaim up to 750 metric tons per hour from the stockpile to feed the cement plant. The scraper moves around the stockpile on a circular track so that its 2.1-meter-wide blades can remove the limestone.

In an upcoming experiment, NASA will test an electromagnetic tether as a means of decreasing the altitude of an Earth-orbiting spacecraft.

Scientists at NASA's Marshall Space Flight Center in Huntsville, Ala., plan to apply Faraday's principle in a demonstration of the Propulsive Small Expendable Deployer System—called ProSEDS—that uses an electrodynamic tether as a means of space-vehicle propulsion. The tether is a 3.1-mile length of bare wire that will be attached to a 6.2-mile nonconductive strand. The whole string will pay out from the second stage of a Delta II rocket, to be launched from Cape Canaveral Air Station in August 2000.

An electrodynamic tether generates a current in its wire as it moves through the magnetic field of the earth's ionosphere. The free end of the tether, positively biased, attracts electrons from space. Current flows as these electrons move toward the spacecraft. Just as Faraday demonstrated, the result is a force perpendicular to the direction of current flow. If the tether points toward Earth's center as the satellite orbits eastward, the current in the tether will exert a force toward the west. This force slows the satellite, dropping it to a lower orbit.

Tethers have been tested in space before. The ProSEDS experiment will demonstrate a different and more efficient scheme for collecting electrons. Previous tethers have been protected by insulation; the new tether will be stripped to bare wire for most of its length. "The working principle of electrodynamic tethers is not new, but the application to space transportation will be revolutionary," said Les Johnson, principal investigator of the ProSEDS experiment. "Tether propulsion requires no fuel, is completely reusable and environmentally clean, and provides all these features at low cost."

This experiment will demonstrate the tether's ability to slow the stage and place it in a lower orbit. If the direction of the current flow in a tether could be reversed, by using an external power source, for instance, the force induced by the tether upon a spacecraft as it orbits eastward could be toward the east as well. A craft, thus sped up, would climb to a higher orbit.

In a phenomenon that may have the same cause as "gray out" and "g-lock"—in which blood flow to the eyes diminishes during high-g flight, peripheral vision narrows, and the pilot can black out—color perception dims as well during moments of high-flight stress. This information is useful to the designers of flight displays who increasingly are relying on color as a means of distinguishing between enemy and friendly aircraft, or between cockpit tasks of high and low priority.

Using the centrifuge at Wright-Patterson, Air Force researcher Tamara Chelette, a biomedical engineer, found that in high-g situations light blue was the first color to fade for her test subjects. Their ability to distinguish between green and yellow was the next to go. It wasn't a matter of the colors themselves, but the contrast between them that seemed to spell which colors would fade. David Post, Chelette's co-researcher, said what makes the difference is the luminance contrast between two colors.

According to Post, a human factors engineer, "Luminance is an objective measure that relates to the human perception of brightness. Luminance contrast is a ratio of two luminances that measures how well something stands out against its background."

The luminance contrasts that can be produced on a cockpit's display depend on the colors in use. Displays produce color by mixing red, green, and blue light. Green usually has the highest peak luminance and blue has the lowest. Displayed upon a dark gray background, for example, green symbols can be presented at higher contrast than blue symbols, making the green symbols less likely to fade than the blue ones.

If two areas of color having similar luminances (yellow and green, for example) were viewed under high g conditions, they would tend to blend together. Or if a low contrast color (such as light blue) was displayed against white, it would tend to fade into the background when viewed under the same conditions.

Centrifuge testing consisted of two experiments. In both tests, the subjects were first spun up to nine gs. For one experiment, the subjects were asked to identify colors as they appeared on a display screen. In the second experiment, subjects were asked to look at two areas of different color on the display and identify which one had the greater number of targets.

Although the test results are still being evaluated, it looks as if the colors being used in today's fighter jets work just fine. Chelette said, however, that color-coded information in the cockpit improves reaction times and decreases error rates, making the use of multicolored displays more likely in future aircraft.

Designers who are figuring out these future displays may well want to keep their heads up, their eyes open, and their seats out of the centrifuge.

Technicians at NASA's Marshall Space Flight Center prepare the X-33 liquid oxygen test tank for simulated service.

Lockheed Martin Michoud Space Systems in New Orleans designed and built the 26-foot-long test tank to carry 181,000 pounds of liquid oxygen. In addition to carrying the propellant, the tank must also conform to the vehicle shape and support fuselage loads from landing gear, control surfaces, and thermal protection systems.

The Marshall team applied internal pressure and external loads on the test tank, by filling it with water and attaching hydraulic struts to the tank's exterior to simulate all the conditions of a mission. After passing these tests, the tank was cleaned, X-rayed, insulated, and shipped to NASA's John Glenn Research Center in Cleveland to undergo further tests with subcooled liquid oxygen and liquid hydrogen.

If the oxygen tank passes its other tests, its sister tank, the actual flight tank, will be an integral component of the X-33 when it commences operational flights scheduled for the middle of next year.

Newcor's automated welding system uses five robots to produce an auto axle tube in 30 seconds.

The tubes house the axle and support the suspension brackets for springs and shock absorbers. Newcor's engineers integrated welding robots and in-line automation assembly processes in a single welding machine that can produce a finished axle tube in 30 seconds, less than half the 80 seconds the previous welding system required. The older welding system used two workers, one to load and the other to unload parts, as well as multiple robots.

The new welding system requires one worker to manually load tubes and brackets on a dial table that has four part stations, two of which are spares. Each part station holds one tube and the brackets that will be attached to it. The table turns 180 degrees to shift the tube from the outside of the machine to the inside of the second station, where the brackets are tack welded in place to the axle tube by two robots.

The welded tubes are picked up automatically from the table and placed onto a walking beam conveyor that transports them through the four remaining welding stations. Here, three light-payload metal inert gas welding robots mounted on the ceiling of the enclosure finish welding the brackets to the axle tubes in eight successive operations. Each axle tube is automatically rotated around its outer diameter at each station to reduce the amount of movement required by the robot to make a proper weld.

The Newcor machine tests weld quality by twisting the locked-in-place tubes lengthwise with 2,000 to 2,500 foot-pounds of torque. After this final weld check, the tubes exit the machine via a chain conveyor system. Each robot is equipped with a programmable logic control connected to a master PLC controller.

Energy-absorbing front ends combined with strong passenger compartments are key factors in reducing passenger injuries in sport utility vehicles involved in frontal collisions. This is one conclusion that can be drawn from crash tests performed by the Insurance Institute for Highway Safety, an independent research organization based in Arlington, Va. The IIHS conducted 40-mph frontal offset impact tests on six midsize SUVs: the Mercedes M Class, Lexus RX 300, Land Rover Discovery Series II, Dodge Durango, Jeep Grand Cherokee, and Montero Sport.

"There's a huge difference between the best and worse performers," noted Brian O'Neill, president of the institute. In his view, key design factors of the Mercedes and Lexus, the two top performers in terms of safety, were front ends that absorbed energy at impact, together with strong passenger compartments.

Many SUVs have stiff structures, earning them poor marks on these tests. "Stiff front ends contribute to the collapse of the occupant compartment," he said. "Basically, it's a question of where you get the stiffness. We want the compartment to be stiff; we want the front and rear ends not to be stiff. They should bend and buckle, and absorb energy." In addition to the ability to absorb impact, front ends designed with an extra two or three inches of "crush space" can make a tremendous difference in the vehicle's ability to absorb energy. "There has to be some room for bending and buckling, and absorbing of energy." Front ends that are shorter will, by definition, be stiffer, he added.

Some automakers have criticized the frontal offset tests as encouraging designs that that are too stiff, and therefore hazardous to other vehicles on the road. Yet O'Neill notes that, based on data, vehicles that have stiff front ends don't do well in the offset crash tests.

Houston-based Integrated Electrical Services Inc. acquired seven companies with combined annual revenues of approximately $135 million. They are expected to boost the total annual revenues of the electrical contracting and maintenance company to $1.1 billion.

The First National Bank of Omaha is powering its Technology Center with four PC25 fuel cells made by Onsi Corp. of South Windsor, Conn. The fuel cells provide 200 kW of electricity for the Technology Center's computers and data processing equipment and heat the 200,000-square-foot center.

A consortium of seven Iowa municipal utilities owns and operates a 2.25-MW wind farm in Algona. The three Zond Z-50 wind turbines provide sufficient electricity to power about 830 households in the consortium's service territories.

The engineering and construction unit of Kvaerner ASA in Toronto signed a $1.5 million contract to bring the Pirdop copper smelter in Bulgaria into compliance with European environmental requirements and increase annual copper production of the smelter from 120,000 tons to 180,000 tons.

The U.S. Navy has commissioned the consulting engineering firm Syska & Hennessy of Princeton, N.J., to design a new central utility plant for its training center in Great Lakes, Ill. Syska & Hennessy will replace outdated hot water generators with newer models to serve the more than 54,000 naval personnel who undergo basic training at the Great Lakes installation.

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