If you were at all conscious in the year 1998, then you remember the major end-of-the-world asteroid movie that came out that year, Armageddon; not to be confused with the major end-of-the-world comet movie Deep Impact, which inexplicably came out the exact same year and introduced us all to the terrifying acronym E.L.E. (Extinction Level Event). Of the two, I always preferred Armageddon: I loved the motley crew of deep-core oil drillers headed up by Bruce Willis and the movie’s (mostly) happy ending, I loved A.J. and Grace’s love story, and I especially loved the Aerosmith theme song written for the movie, which was a romantic mainstay at all of my high school dances.

I also enjoy the 2012 movie Seeking a Friend for the End of the World, which had a somewhat more depressing but, in my opinion, maybe more realistic view of an asteroid threatening Earth (spoiler alert – the last ditch efforts of a crew of astronauts do not work).

Propagation of the blast wave from an air-bursting asteroid to the ground. [Image: Michael Aftosmis, NASA/Ames]

The year after this movie was released, a 20-meter asteroid struck the Russian city of Chelyabinsk, and the resulting pressure and winds from the shock wave wreaked all kinds of havoc – breaking windows, damaging buildings up to 58 miles away, sending debris flying, and injuring over 1,200 people. According to the Advanced Supercomputing Division (NAS) at NASA, most windows break under 2 pounds per square inch (psi) of pressure, while it takes 10 psi for larger buildings to collapse, and fires can ignite from the explosion’s resulting thermal radiation. So we know the movies got at least one thing right – asteroid strikes can cause all sorts of damage.

Cross-section of a Chelyabinsk-like asteroid (gray rock) breaking up during atmospheric entry at 20 km per second. A hot, high-pressure shock wave (yellow, orange) forms around it.

If you’re wondering what any of this has to do with 3D printing, we’re not talking about using asteroid material to 3D print autonomous ships, or even using 3D technology to explore the second largest object in the asteroid belt. Rather, researchers are creating 3D asteroid models, which has been done before, and using a powerful NASA supercomputer to produce simulations of hypothetical asteroid impact scenarios.

Aerospace engineer Michael Aftosmis, who runs the Asteroid Threat Assessment Project (ATAP) blast wave and ground damage modeling work at NAS, said, “Asteroid impacts are one of the only natural disasters we can actually predict and then take action to protect people.”

This research is being completed in support of NASA’s Planetary Defense Coordination Office (PDCO), and the results could help first responders and other agencies learn how to identify, and make informed decisions on on how to defend against, possible life-threatening asteroid events, like the one that happened in Chelyabinsk.

Cart3D shuttle animation

ATAP experts at the NAS facility at NASA’s Ames Research Center in Silicon Valley ran large-scale simulations of the Chelyabinsk event on the Pleiades supercomputer using NASA’s Cart3D modeling software. The software, which is dozens of times faster than the 3D numerical modeling normally used for aerodynamic analysis, ran high-fidelity simulations of the blast from the asteroid’s entry corridor all the way to the surrounding countryside. The team was able to compare their predictions of the blast shock arrival time and overpressures at specific locations, covering over 40,000 square km, with data from the actual event, which was recorded on building and dashboard cameras in the area.

“These are some of the world’s most detailed simulations of this event. We were able to produce many scenarios quickly because Cart3D, normally used for aerodynamics analysis, is dozens of times faster than most hydrocodes used for 3D numerical modeling of the fluid flow that occurs when asteroids melt and vaporize as they break up in the atmosphere,” explained Aftosmis.

The results of the team’s first simulations, when compared to the Chelyabinsk data, matched to within a fraction of a second. The team also developed a 3D Probabilistic Asteroid Impact Risk (PAIR) model, and ran simulations of possible asteroids in multiple sizes on the Pleiades, again with the Cart3D software, and also using Lawrence Livermore National Lab‘s (LLNL) ALE3D modeling software. The model performs damage analyses, based on physics, for millions of impact cases; you can see a video of one of these simulations here.

“What’s unique about our analysis is that we can rapidly assess so many scenarios while faithfully representing the key physics. This is done by leveraging the airblast, ground, and water impact simulations created by the team, as well as by taking advantage of the NAS compute resources,” said Donovan Mathias, an aerospace engineer who runs the NAS Division’s Engineering Risk Assessment team and ATAP risk modeling work.

All of NASA’s important asteroid research is being shared with scientists at other government agencies, national labs, and universities, who will use the information to work up assessment and response plans, and to inspect warning times, evacuations, infrastructure damage, and options for protecting property and human life. This will increase the chance of humanity’s survival in the case of an E.L.E. or any other kind of damaging asteroid strike. Discuss in the 3D Asteroid Models forum at 3DPB.com.

[Sources: PhysOrg, NASA]

 

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