What happens below ground when a missile hits?

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The havoc above ground is obvious, but the details of what happens below ground are harder to see. Physicists have developed techniques that enable them to simulate high-speed impacts in artificial soil and sand in the lab, and then watch what happens underground close-up, in super slow motion.

The research, funded by the Defense Threat Reduction Agency, may ultimately lead to better control of earth-penetrating missiles designed to destroy deeply buried targets such as enemy bunkers or stockpiles of underground weapons.

When a missile or meteor strikes the earth, the havoc above ground is obvious, but the details of what happens below ground are harder to see.

According the Homeland Security NewsWire Duke University, physicists have developed techniques that enable them to simulate high-speed impacts in artificial soil and sand in the lab, and then watch what happens underground close-up, in super slow motion. In a study in the journal Physical Review Letters, they report that materials like soil and sand actually get stronger when they are struck harder.

The findings help explain why attempts to make ground-penetrating missiles go deeper by simply shooting them harder and faster have had limited success, the researchers say. Projectiles actually experience more resistance and stop sooner as their strike speed increases.

A Duke University release reports that the research, funded by the Defense Threat Reduction Agency, may ultimately lead to better control of earth-penetrating missiles designed to destroy deeply buried targets such as enemy bunkers or stockpiles of underground weapons.

To simulate a missile or meteor slamming into soil or sand, the researchers dropped a metal projectile with a rounded tip from a seven-foot-high ceiling into a pit of beads. During collision, the kinetic energy of the projectile is transferred to the beads and dissipates as they butt into each other below the surface, absorbing the force of the collision.