Nemec, Marian

NASA Technical Reports Server

National Aeronautics and Space Administration
www.nasa.gov 
Simulating Atmospheric Impacts: 
From Pebble- to Mountain-Size Meteoroids
Marian Nemec 
NASA Ames Research Center
SC17, Denver, CO 
November 13-16, 2017
https://ntrs.nasa.gov/search.jsp?R=20170011692 2019-08-30T18:42:59+00:00Z
Meteoroid flux: ~50 tonnes each day (primarily sand-grain to centimeter-size bodies) 
Approximate

Diameter
10m
3m
1m
ATAP Overview
Page 2 
Asteroid Threat Assessment
June 2017 
Asteroid Properties  
Entry Physics 
Surface Hazards 
Damage & Risk 
Characterization 
•  Measurements 
•  Inference 
•  Data aggregation 
•  Property database website 
Hazard Simulations 
•  3D blast simulations 
•  Impact crater simulations 
•  Tsunami simulations 
•  Thermal radiation models 
•  Global effects 
Probabilistic Risk Assessment 
•  Analytic physics-based entry 
and damage models  
•  Probabilistic Monte Carlo 
simulation using uncertainty 
distributions 
Entry Simulations & Testing 
•  Coupled aerothermodynamics 
•  Ablation & radiation modeling 
•  Arc jet testing 
“Asteroid Threat Assessment Project” presentation to Small Bolide Assessment Group O U R  P L A N E TSCIENCE MISSION DIRECTORATE
Google Earth map of hypothetical damage zones modeled for an asteroid impact exercise performed at the 2017 Planetary Defense 
Conference. NASA’s Probabilistic Asteroid Impact Risk model was run on the Pleiades supercomputer to evaluate damage zones and 
affected populations over the course of the five-day exercise, as information about the invented scenario evolved from initial 
detection with a large potential impact swath and little knowledge about the asteroid, to a specific, imminent impact threat. Lorien 
Wheeler, NASA/Ames
Simulation of tsunami and blast waves generated by the impact of a 1-gigaton, 100-meter diameter iron asteroid into the ocean, produced 
with the ALE3D hydrocode. Blue contours show water velocities, and orange contours show the velocity of air pressure waves emanating 
from the vertical entry column and the surface impact. This frame shows a snapshot right after impact when a column of water is 
rebounding up from the initial impact cavity. Darrel Robertson, NASA/Ames
Lorien Wheeler, Donovan Mathias, NASA/Ames
NASA’s Asteroid Threat Assessment Project has developed an 
advanced probabilistic asteroid impact risk model to assess the 
potential threat posed by asteroids striking Earth. Running on the 
Pleiades supercomputer, the model is able to analyze millions of 
impact cases to determine the range and likelihood of damage 
due to blast waves, thermal radiation, tsunamis, and global 
effects for asteroids of different sizes and properties striking all 
over the world. High-fidelity simulations of asteroid entry and 
hazards are also performed to advance our understanding of key 
impact effects and refine analytic risk models. Impact risk results 
are used to support asteroid survey, mitigation, and response 
planning, and estimate potential consequences of specific impact 
scenarios if a threat were to be discovered.
Asteroid Impact   
Risk Assessment
Demo 21  •  Jill • Artist  
ATAP Supercomputing
Page 2 
Asteroid Threat Assessment
June 2017 
Asteroid Properties  
Entry Physics 
Surface Hazards 
Damage & Risk 
Characterization 
•  Measurements 
•  Inference 
•  Data aggregation 
•  Property database website 
Hazard Simulations 
•  3D blast simulations 
•  Impact crater simulations 
•  Tsunami simulations 
•  Thermal radiation models 
•  Global effects 
Probabilistic Risk Assessment 
•  Analytic physics-based entry 
and damage models  
•  Probabilistic Monte Carlo 
simulation using uncertainty 
distributions 
Entry Simulations & Testing 
•  Coupled aerothermodynamics 
•  Ablation & radiation modeling 
•  Arc jet testing 
“Asteroid Threat Assessment Project” presentation to Small Bolide Assessment Group
Propagation and Overpressure Prediction
5
ATAP - Prediction of meteor-generated sonic boom
• Obtained observations for a small meteor from 2008 and backed out conditions 
• Performed CFD simulations for both sphere and rock-like shapes w/ Cart3D using equilibrium air 
• Propagate near-field pressure 74 km to observatory using sonic-boom propagation code 
• Currently obtaining recorded ground signature from observatory for comparison
0 50 100 150 200 250 300
x (m)
0
0.2
0.4
0.6
0.8
1
1.2
∆
p/
p ∞
Perfect gas
Equilibrium gas
Pressure Signature at 20d Predicted Ground Signature
0 20 40 60 80 100
Time (ms)
-0.01
-0.005
0
0.005
0.01
Ov
er
pr
es
su
re
 (p
sf
) Sphere 20dRock 20d
Rock 30d
Equilibrium Air CFD
Airbursts: Flow-field Initialization
0102030405060
Altitude (km)
0.0
0.2
0.5
0.8
1.0
En
erg
y D
ep
os
itio
n (
M
T/
km
) Normalized rate of Edep
Net Energy Deposited/10
Normalized Mean Velocity/20
x
z ∆td    d = V ∆t  
d
r
Mach Contours
Temperature Contours
Ground Overpressure
Nominal “Strong”
30km
20km
10km
0 km
30km
20km
10km
0 km
Overpressure (%) Overpressure (%)
HPC Perfomance
Tsunami Coupling
11
• Ground footprint evolution drives tsunami

• Coupled Cart3D surface pressure to GeoClaw 
package (U.Wash + NYU) for tsunami 
simulation
Aftosmis / Berger / Nemec
• Domain Extent: 

240 x 240 x 80 km high ~58,000 km2 of surface

• ~105 M total cells

• 20 m resolution along trajectory, 

• 80 m resolution at sea level

• 3D time-dependent simulations using Cart3D

• Resources

(1000 cores x ~12 hrs) on NAS Pleiades system
South China Sea, 200m diameter
Computational 
Domain
South China Sea
240km
24
0k
m Entry
M. Berger / M. Aftosmis
Tsunami
M. Berger / M. Aftosmis


Simulating Atmospheric Impacts: From Pebble- to Mountain-Size Meteoroids

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