RENEE MONTAGNE, host:
One of the world's most powerful centrifuges whirled into action last night, recreating the storm dynamics caused by Hurricane Katrina. NPR's David Kestenbaum reports from the laboratory in Vicksburg, Mississippi, which is run by the U.S. Army Corps of Engineers.
DAVID KESTENBAUM reporting:
Engineers and technicians here have been working seven days a week, 12 or 13 hours a day, to build a very precise model of a canal wall in a transparent plastic box. It's 1/50 the actual size. You might think you just have to fill it with water and see what happens, but the water would only be inches high, not feet high, as it was during Katrina. So to really recreate the force of the water and the weight of the walls on the ground, engineers have to subject the model to 50 times the normal force of gravity. The easiest way to do that is to spin the model really fast.
Ms. WIPAWI VANADIT-ELLIS (Acting Director, Centrifuge Research Center): We're walking down into the centrifuge chamber. It has the same kinetic energy as an airplane takeoff. So for safety reasons we build it below ground.
KESTENBAUM: This is Wipawi Vanadit-Ellis, acting director of the Centrifuge Research Center. Three stories underground is a round room some 40 feet across.
Ms. VANADIT-ELLIS: The machine is, I guess it's kind of like a ride you see in a kid's merry-go-round.
KESTENBAUM: There's a metal arm anchored in the middle of the room, at the end of it is a test chamber. It's top speed...
Ms. VANADIT-ELLIS: Like 300.
KESTENBAUM: Three hundred miles an hour in this room?
Ms. VANADIT-ELLIS: Yes.
KESTENBAUM: Around and around and around.
Ms. VANADIT-ELLIS: Yes. You could hear it hum. It will definitely change your hairdo if you stand close to it.
KESTENBAUM: At the end of the arm sits the miniature model of a wall from the London Avenue Canal, one of the structures that broke in New Orleans flooding downtown. It looks a bit like a terrarium. Through the side of the plastic box you see the wall extending into the ground. At the bottom there's sand. There's clay higher up. And in between a soft layer of peat that engineers fear caused the failure.
Ms. VANADIT-ELLIS: The benefit of using the centrifuge, in addition to the correct stress and strain simulation, is you can use actual material, so that peat layer you see is actually samples we collected from New Orleans.
KESTENBAUM: Right there? That's actually from New Orleans.
Ms. VANADIT-ELLIS: Mm-hmm. We went and extracted 20 boxes of peat at the correct depth where the failure occurred.
KESTENBAUM: Buried inside the model there are sensors, and to one side there are cameras. Soon it's ready for its first spin. Workers pull shut a big red door and lock it with two separate keys for safety.
Up in the control room it takes just the press of a green button labeled Boom Rotation. They've been working toward this moment for months.
Unidentified Man (Control Room Worker): You ready for me to push it? Okay.
KESTENBAUM: And so while many people are watching the Academy Awards, this group of eight people stare intently at four black and white televisions. The centrifuge spins faster and faster.
Mr. MICHAEL SHARP (Works with Centrifuge): I'm excited to get a test done. I've got all my fingers crossed.
KESTENBAUM: Michael Sharp is one of the leaders of the investigation.
Mr. SHARP: We're hoping to find out the mechanism of failure, exactly did it just, the whole levee get pushed forward? Was it some kind of failure in the foundation? Was it something to do with the way the wall and the levee was constructed?
KESTENBAUM: They take it up to speed slowly over a period of hours. Sharp says he's pretty sure he knows what will happen. If they add water up to the top of the canal wall, the wall will tip catastrophically outward. That's apparently what happened during Katrina. Segments of the wall then came apart and the water rushed out.
Just before nine o'clock into the evening, the engineers let water into the model. The water rises and the wall fails. There are a few quiet cheers. The centrifuge can make artificial gravity but it can't turn back time. The engineers will now study the data from the experiment in the hopes that the real thing does not happen again.
David Kestenbaum, NPR News, Vicksburg, Mississippi.
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