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March 12, 2012

Nukes to Save the Earth

Robert Gelber

Since its inception in 1943, the Los Alamos National Lab (LANL) has participated in the design of nuclear weapons, a technology that has unfortunately threatened the planet on more than one occasion.  But recently the lab has been looking into an application that would use of nukes to save mankind.  Late last year LANL developed a computer model of how a nuclear detonation could destroy planet-killing asteroids headed toward Earth.

The model in question has been stuck with the rather understated designation of  “asteroid mitigation calculation.” In a video discussing the work, Robert Weaver, a research scientist at LANL, says asteroids are simply a collection of rocks that are held together by gravity, so a well-placed nuclear blast could be enough to break up even a very large asteroid into harmless pieces.

The software attempts to create an accurate simulation of a 500-meter long asteroid as a 1-megaton nuclear explosion is delivered to its surface. In the simulation, the asteroid’s internal structure is represented as a collection of granite rocks, and when the nuclear blast detonates at the surface, it breaks up the mass through a kind of domino effect.

“What we’re looking at are calculations that perform real hydrodynamics on these objects in order to understand whether we can use an energy source of this magnitude to really disrupt this asteroid and prevent the hazard to the entire Earth,” says Weaver. According to him, the simulation shows that a nuclear blast of that power would indeed “fully mitigate” the threat to Earth.         

Modeling the reaction required a lot of computing horsepower, so the researchers turned to Cielo, a Cray-built supercomputer, rated at 1.1 Linpack petaflops.  The machine consists of 8,944 dual-socket nodes and 286 TB of memory, and is powered by 8-core AMD 6136 Opteron CPUs. According to Weaver, the simulation was able to use 32,000 processors (although in this case he probably means cores given that Cielo only has 17,888 CPUs. Weaver noted the simulation he ran on the Cray super was unable to run on any previous machine he had access to at the lab.


Asteroids hitting the earth may seem like a far-fetched notion only realized in Hollywood disaster movies. However, a recent EarthSky report explains that an asteroid named 2012 DA14 will come alarmingly close to the Earth on February 15, 2013. Estimations pin the rock at missing the planet by only 17,000 miles. That is closer than the moon and some satellites. The report also goes on to predict a remote chance of impact by the same asteroid in 2020. Given that, Weaver’s work might be given a real-world test in the not-to-distant future.

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