March 2005 
Volume 03, Issue 10 
Integrated Defense Systems

More bang for the Boeing buck


A 30-meter compressed-gas gunWhat a blast! Imagine an asteroid screaming toward Earth. What would it take to blow it up—or just nudge it off course? Can you bulletproof a war plane or protect an aircraft from flying fragments? How do you shield space ships from meteoroids?

Does this sound like sci-fi? The Boeing Phantom Works Shock Physics lab in Seattle tackles all these questions and more—today. It studies impact hazards, explosions, and the sudden cutting and crushing of materials. "I suppose you could call this material testing to the extreme," said Kevin Housen, lead research scientist at the lab. Its mission, he said, is "studying the effects of impact events that happen very fast."

It's all about questions.

How could invisible cracks affect the integrity of pipes—such as the high-pressure chemical-gas pipes on board Boeing's Airborne Laser aircraft? The lab developed safety standards for ABL inspectors.

How hot do machines and metals get during high-speed cutting? The lab measures punishment to materials at many levels.

How much impact can flight-deck doors take? Lab tests are helping produce flight-deck doors that are lighter yet stronger than current ones.

And how do different munitions form different craters, and how much do craters formed on Earth differ from some craters formed in space? Since the 1960s the lab has studied many kinds of craters; and Michael Bjorkman, the other research scientist at the lab, said Housen is "one of the few experts in the 'cratering' field (see box below) left on the planet."

To conduct all their tests, the Shock Physics lab employs various tools of the trade. "Guns we've developed can launch projectiles to speeds ranging from a lazy fastball to several times faster than a high-powered rifle," Housen said. He and Bjorkman hurl chunks of tire tread at wing skins, using a 10-inch-bore (250-millimeter) compressed-gas cannon. A 2.5-inch-bore (60-millimeter) gas gun makes craters for NASA impact research. Sometimes the lab uses explosives in tests.

Lab cameras catch the action at up to 150,000 frames per second—or even (for a tiny fraction of a second) a million—so the team can study each unfolding moment in slow motion.

The Shock Physics lab is doing a bang-up job for Boeing, conducting studies that improve the quality, safety and performance of aerospace products—and even advancing our knowledge of the cosmos.

How it works

All holes are not "cratered" equal.

On Earth, impacts and explosions send rocks and soil airborne, making different kinds of craters—and gravity pulls the debris down differently around crater edges.

To observe craters, the Shock Physics group cut away half a box and inserted glass to allow side-view, high-speed filming of scaled-down craters during formation. But they learned that to mimic a 10-foot crater in a 1 foot space they'd need gravity to be 10 times stronger. So Boeing used a centrifuge arm that can spin a box of soil in a wide circle and boost it to 600 times gravity. Craters in its manhole-cover-size patch of earth are proportionate to craters the size of a city block.

In space, some objects, such as low-density comets, seem to have craters that are immense dents, not the usual huge excavations surrounded by rubble. Kevin Housen, Shock Physics lead scientist, supported this view after testing porous-rock-like models for Deep Impact, a NASA mission that on July 4 will crash an 820-pound (370-kilogram) "impactor" onto a real, live comet in space. From the crater it makes, scientists hope to learn more about comets—and cratering.



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