Supercomputer takes on cosmic threat

Bruce Willis: encore coring
One demonstration simulation — 10 megatons at the center of mass of the object — is the most spectacular "end member" of the range that the research team explored. But it's the least likely scenario, Boslough explained. "It also neglects a fundamental problem of how you would get the device inside an asteroid."

Bruce Willis and his team may have drilled into the core of an asteroid and planted a nuclear bomb in the 1998 movie "Armageddon," but that scenario just doesn’t seem likely in the real world, Boslough said.

Playing out Golevka’s hypothetical demise even on a super-fast computer took longer than the movie. Sandia’s half-second, billion-cell simulation of a 10-megaton explosion at Golevka's center took 12 hours to run on 7,200 processors of Red Storm.

The supercomputer is a product of a partnership between Cray Computers Inc. and Sandia National Laboratories, developed for the Advanced Simulation and Computing program of the Department of Energy’s National Nuclear Security Administration laboratory.

Low-yield, high payoff
The Red Storm computational output provided useful insights.

In particular, Boslough said, was the realization that using multiple, low-yield, deflecting explosions is much better than using one high-yield device. 

Sandia National Laboratories Tom Hunter, director of Sandia National Laboratories in Albuquerque, N.M., discusses how a supercomputer can simulate a variety of real-world problems, including a concept for deflecting an asteroid.

"There are many advantages" to this approach, Boslough observed. "For one, you don’t need to rendezvous with the asteroid and drill a hole or otherwise place a device. You can set it off as a surface burst. Contrast the time it takes to ‘land’ something on the surface of an asteroid — like NASA’s Near Earth Asteroid Rendezvous spacecraft — to how long it takes just to get there, like NASA’s Deep Impact," he said. 

You want to solve the problem quickly, Boslough said, "even if we know about an impact decades in advance — the public perception will be that time is of the essence."

If asteroid deflection is the game plan, there’s need to avoid accidental breakage. 

A low-yield blast lessens the volume of material that is subjected to the highest tensile and shear stress, reducing the likelihood that the object will come apart.

"If you do break the asteroid, you want to make sure none of the big pieces hit the Earth," Boslough said. "Multiple low-yield bursts over an entire hemisphere [of the asteroid] would reduce the likelihood that anything big would get left behind on the impact trajectory."

When saving Earth, have a Plan B
The fact that you can get a low-yield device to a menacing object fast also means that you are more likely to have a second chance, Boslough noted. He said that equates to a viable "backup plan" for other, more elaborate, expensive and time-consuming methods. 

"When you are saving the Earth, it’s good to have a Plan B. I suspect that if a near-Earth object were confirmed to be on an impact trajectory, public opinion would demand fast action, and this would become Plan A, if it wasn’t already," Boslough said.

Boslough said that follow-on work regarding defending Earth from near-Earth objects is slated. Specifically on tap is delving into momentum transfer for a variety of assumed asteroidal and cometary materials and structures.

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