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In Warren, Michigan, at GM's university-like Research and Development Center, a dummy called SID sits on a sled. "SID" stands for "side-impact dummy," a specialist in sideways crashes into other cars. SID's sensors measure the forces that such a broadside crash exerts on a human body.
"A crash test with a real car is the first level of simulation," says GM physicist Stephen Rouhana. "A sled like this is one abstraction further-it allows us to simplify dramatically what goes on and still get respectable data." Rouhana is in the HYGE Test Area to watch SID take his lumps. ("HYGE" stands for "hydraulic-controlled gas-energized," which describes how the sled operates.) A hydraulic ram shoots out from a 100-ton concrete block to give the sled a 3,000-pounds-per-square-inch punch. In response, the sled accelerates down 120-foot-long rails, rocketing from zero to 30 mph in six one-hundredths of a second. "That's a hundred times faster than a Corvette can accelerate," says Rouhana.
GM senior supervisor Joe Balser is flanked by dummy developed to study side-impact injuries (left) and Hybrid 111, used to analyze front and rear crashes.
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sled is rigged with a car door and window. Nylon sacks represent the experimental air bag. SID sits on a simulated car seat, sideways to the waiting ram. He is bathed in high-intensity light for the benefit of high-speed video cameras on the sidelines and the sled's two on-board movie cameras. SID looks like a screen actor on a set. In fact, white-coated technicians are applying "makeup" red chalk that will leave marks where SID's head and torso strike the simulated air bag. "He is an average male, with a below-average-male IQ," notes Rouhana.
SID sits as placidly as Forrest Gump, a thick umbilical cord of wires issuing tail-like from the seat of his tights. During the crash, 31 continuous measurements from SID's interior sensors will rush simultaneously through a cable into a waiting computer. The computer will record an incoming stream of data 4,000 times during the two-fifths-of-a-second measurement interlude.
SID is bald, his affable face faintly smiling. "He's blissful, as in ignorance," says Rouhana. That is just as well. Better that SID is unaware his feet have been removed: in previous tests they stuck to the floor and slightly slowed the speed at which he whammed into the door. Also, SID might feel deprived if he knew he had-no arms, which would get in the way. Yet, his designers did not omit arms in their calculations. "The mass of the arms he doesn't have is incorporated into his rib cage," says Rouhana.
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The actual test lasts just an eye blink. After that, the sled is merely rolling to a stop. This morning's test is to help develop a new air bag for side crashes. And so the
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Technicians are now using blood-red laser beams to position the dummy. It must sit exactly the same in test after test. Red flashers signal that pressure is building in the ram. Technicians and the test's engineer, Bonnie Cheung, hurry behind a Plexiglas shield as the ram's operator, in a control booth above the concrete slab, conducts the countdown. Wham!
The sled rockets down the tracks. SID jerks sideways. The researchers ignore him. They hover around a video screen for an instant replay. "He was into the bag in about ten milliseconds," a technician announces. In the sled, stopped halfway down the track, SID lies sprawled, butt up, his head on the laboratory floor where it smacked. The researchers are studying a computer screen displaying the forces on SID's body at impact. Eventually they will note precisely where the red chalk from SID's head and torso marked the simulated air bag. But now the fallen SID lies unnoticed, the ultimate blue-collar worker, unprotected by OSHA, suffering in silence. Even his fellow dummies ignore him. They sit in chairs alongside the track, staring into space, awaiting their own turns on the sled.
Their world is Darwinian. The dummy's ecological niche is car smackups. Data from the crashes may lead to new designs. Accident statistics can change. Federal rules are altered. In response to all these factors, dummies mutate. It is survival of the most sensitive, the dummy whose instruments and physical reactions best
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