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"  Shortly after dawn breaks on a crisp March morning, ironworkers Paul Atherton and Clint Richard climb onto the trussing of a roller coaster&amp;#039;s steel skeleton, strap themselves into safety harnesses, and wait. Legs swinging, Atherton lights a cigarette; 11 stories below, a crane rumbles to life, and its operator begins to lift a 31,000-pound piece of curved orange track into the air. At 121 ft., this will be the highest point of Fahrenheit, a goliath new ride at Hersheypark in Pennsylvania. The ironworkers reach across the chasm, grab guide ropes and carefully maneuver the track into position. In just two months&amp;#039; time, riders will crest this same piece of steel, then hurtle down a record-setting 97-degree slope--yes, that&amp;#039;s 7 degrees past vertical--on the steepest and most severe roller-coaster descent in the United States. &amp;quot;When you come over the apex of the curve, you&amp;#039;re lifted forward into the harness,&amp;quot; says Kent Bachmann, the park&amp;#039;s director of design and engineering. &amp;quot;The track actually disappears for a few seconds.&amp;quot; And that&amp;#039;s just the beginning: Fahrenheit will provide 2 solid minutes of corkscrews, barrel rolls and inversions. &amp;quot;That way every time you get on this ride,&amp;quot; Bachmann says, &amp;quot;you can have a different experience.&amp;quot; Taller, faster, with multiple thrills: This is the next generation of roller coaster. &amp;quot;New engineering tools, quicker computers and exotic materials--all          Hersheypark&amp;#039;s Goliath Coaster Detailed illustration of Fahrenheit&amp;#039;s twists and turns     have allowed designers to take the industry to the next level,&amp;quot; says Jim Seay, president of Premier Rides, a leading coaster design firm. &amp;quot;High-tech materials like carbon-fiber composites opened the door to more sophisticated designs,&amp;quot; he says, &amp;quot;because they reduce weight and the resulting stresses on large support structures.&amp;quot; Technology such as the linear induction motors used in Mr. Freeze, a ride Premier created for Six Flags St. Louis, has increased speeds dramatically, launching riders to 70 mph in only 4 seconds. The hydraulic launch in Xcelerator, at Knott&amp;#039;s Berry Farm in California, propels the train to 82 mph in 2.3 seconds. Even the trains themselves have advanced: At Six Flags Magic Mountain in Los Angeles, the rotated seating on Tatsu gives the sensation of flight, and Riddler&amp;#039;s Revenge sends riders through loops standing up. Engineering elements like Fahrenheit&amp;#039;s top hat, which allows for 90-degree lifts and more aggressive drop angles, are made possible by the same software that companies such as Boeing use to develop aircraft. Besides adding accuracy, Seay says, computer-aided design &amp;quot;allows the engineer to be more creative because he can model his ideas.&amp;quot; But as coasters get more extreme, critics claim health risks such as brain injury also escalate. Ride engineers counter that coasters are designed within guidelines established by studies on NASA astronauts, jet pilots and crash-test dummies, which determine the maximum forces people can withstand. In Popular Mechanics&amp;#039;s August 2003 cover story, scientists sided with coaster engineers--and they still do. Douglas Smith, a University of Pennsylvania neurologist, developed a model that analyzes how a person&amp;#039;s head would rotate during a ride--combined with rapid acceleration and deceleration, this rotation causes most brain injuries--then input the g-forces from three coasters. &amp;quot;The head rotational accelerations were nowhere near the thresholds we know cause injury,&amp;quot; Smith says. He recently repeated the study, this time outfitting riders with sensors that measured head acceleration in three planes; Smith says preliminary data supports his original findings. Neurologist Gary O&amp;#039;Shanick, chair of a panel tasked with determining if coasters can cause brain trauma, says the risk lies in the rider, not in the ride, so only people with pre-existing conditions may be prone to injury. Fahrenheit will undergo extensive safety testing when it&amp;#039;s complete. &amp;quot;We&amp;#039;ll have run a thousand rides before anyone gets on it,&amp;quot; Bachmann says. Water-filled dummies weighing 175 pounds each will show how the trains behave at capacity. Also strapped into the harness will be Fred, a crash-test-dummy equipped with a chest-high accelerometer and sensors that measure neck movement along six axes. When Fred descends that first, spectacular slope, he will be lifted forward into his harness--and there&amp;#039;s a good chance that he, like many coaster enthusiasts, will throw up his arms. While a plunge past 97 degrees would be too uncomfortable for real riders, Seay says coaster innovation has by no means reached its peak. He envisions a roller coaster where riders choose their own music, use radio-frequency technology to douse people on the ground with water, and even modify the ride in progress. &amp;quot;The idea may seem unrealistic at this point, but our parents could never have imagined the rides that exist today,&amp;quot; he says. &amp;quot;We&amp;#039;ve come a long way since the Coney Island Cyclone.&amp;quot; "^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.popularmechanics.com/technology/design/a3339/4268108/>