“We are not going to send Bruce Willis to the asteroid to blow it up,” laughs Donovan Mathias. Donovan leads NASA Ames’ Engineering Risk Assessment team, and he’s talking about the work he does to protect the earth from asteroid impacts – work that is decidedly more Deep Blue than Deep Impact.
NASA has been actively working to understand and mitigate the risks posed by asteroids for a decade. Much of this work currently takes place in California as part of the Asteroid Threat Assessment Project (ATAP) at NASA Ames. The scientists at ATAP – a young project, only in its fourth year – use supercomputers to conduct risk and damage assessment of simulated atmospheric entries by asteroids.
Supercomputing at ATAP
ATAP makes extensive use of the Probabilistic Asteroid Impact Risk (PAIR) model, which simulates the physics of asteroids entering – and sometimes, exploding in – the atmosphere, allowing ATAP to estimate damage from blast waves, heat, tsunamis, and more. PAIR runs millions of impact cases, allowing it to capture a wide range of asteroid properties and damage scenarios, as well as the likelihoods of each. This sets ATAP’s work apart from previous asteroid risk assessments, which predominantly worked with average values.
Beyond PAIR, ATAP also leverages the Cart3D computational fluid dynamics software – the same software used to model spacecrafts’ heat shields – to analyze the propagation of force from asteroids that burst in the air. They also work with ALE3D hydrocode simulations to study tsunami generation and cratering effects.
The data produced by ATAP’s simulations help NASA and other government agencies understand the potential impacts of a broad variety of different asteroid entry scenarios. The understanding provided by ATAP’s research has helped NASA’s Science Definition Team (SDT) narrow down which asteroid sizes pose significant threats to the planet, allowing them to further focus their asteroid tracking activities.
Eric Stern, a research scientist at NASA, likens the “incredibly unbelievable speeds” being simulated to spacecraft, but at an “extreme scale” – a scale that pushes the tools at hand to their limits. ATAP runs its simulations on the Pleiades supercomputer, an SGI system benchmarked at 5.95 Linpack petaflops that ranks 24th on the latest Top500 list.
The future of supercomputing in asteroid defense
ATAP’s efforts are just the beginning. This summer, the White House’s Office of Science and Technology Policy issued the “National Near-Earth Object Preparedness Strategy and Action Plan,” a ten-year plan aimed at ramping up and coordinating asteroid preparedness and defense activities across government agencies. The plan emphasizes the role of supercomputing and plans for an “integrated suite of computational tools for modeling NEO impact risks and mitigation techniques[.]” Specifically, it outlines how agencies will:
Ascertain what information each participating organization requires on what timeframe, identify gaps, and develop recommendations for modeling improvements. […]
Develop and validate a suite of computer simulation tools for assessing the outcome of deflection or disruption techniques applied to a NEO. […]
Establish a suite of computer simulation tools for assessing the local, regional, and global risks associated with an impact scenario. […]
Assess the sensitivities of these models to uncertainties in NEO dynamical and physical properties.
ATAP is also generally advancing its risk modeling capabilities and moving toward assessing different asteroid structures, ranging from “monoliths” to “loosely bound rubble piles.”