Mindscape: Book 2 of the New Frontiers Series
Page 31
Converted to Megatons using the calculator above = 12,810 megatons
The 10,000 kg relativistic missile weighed in at just over 13,000 megatons of energy, so this is close enough.
Now, what does the Purdue impact calculator have to say about an impact like that?
Try it yourself: http://smarturl.it/impactcalculator. The variables are:
Diameter: 400 meters
Density: 8000 kg/m3
Impact Velocity: 20 km/s
Impact Angle: for maximum effect, let’s set 90 degrees
Water depth: 1000 meters — I wanted to know about a water impact, specifically in the Gulf of Mexico. I measured the water depth 200km from the shore south of Galveston Island using this map: http://smarturl.it/oceandepth. Depending how you measure those 200 km you’ll either end up in the shallow basin area or just beyond it in the continental shelf. I ended up in the deeper water. The result was just over 1000 meters depth.
Distance from event: 200 km
Results
Energy 12,800 Megatons (same as independently measured)
Global Damages: Day change: not significant — no major changes in orbit/mass of earth
Crater: Complex Crater — even water impacts create craters
Ejecta
The ejecta will arrive approximately 3.43 minutes after the impact.
At your position there is a fine dusting of ejecta with occasional larger fragments.
Average Ejecta Thickness: 2.72 mm ( = 1.07 tenths of an inch )
Mean Fragment Diameter: 9.13 mm ( = 3.6 tenths of an inch )
My conclusion: This is not enough to cause an impact winter. The main reason we worry about impact winter and nuclear winter is because the smoke and ash put out by subsequent firestorms adds to the problem of the dust kicked up during the impact. At 200 km from the shore the thermal radiation is too weak to cause much in the way of fires, and the ejecta from such a small impactor is not likely to cause a lot of fires.
Thermal Radiation
Time for maximum radiation: 378 milliseconds after impact
Visible fireball radius: 4.38 km ( = 2.72 miles )
The fireball appears 4.98 times larger than the sun
Thermal Exposure: 3.08 x 10^5 Joules/m^2
Duration of Irradiation: 1.63 minutes
Radiant flux (relative to the sun): 3.15
My conclusion: You could get a nasty sunburn from this, and the explosion would likely flash-blind you if you were looking at it.
Seismic Effects
The major seismic shaking will arrive approximately 40 seconds after impact.
Richter Scale Magnitude: 7.1
Mercalli Scale Intensity at a distance of 200 km:
Felt indoors by many, outdoors by few during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rocked noticeably.
Airblast
The air blast will arrive approximately 10.1 minutes after impact.
Peak Overpressure: 11000 Pa = 0.11 bars = 1.56 psi
Max wind velocity: 24.8 m/s = 55.4 mph
Sound Intensity: 81 dB (Loud as heavy traffic)
Damage Description: Glass windows will shatter.
My conclusion: for the damage caused by “overpressure” (pressurized air carried by the blast wave) check out the chart on page 13 of this FEMA document http://smarturl.it/femaexplosions. According to this source, overpressure of 0.22 PSI is enough to break glass, while 1.1-1.8 PSI (our impact generates 1.56 psi at 200km) is enough to do “minor damage to some buildings” and result in “panels of sheet metal buckled.”
So this will blow out windows for sure. Watch out for flying shards of glass!
Tsunami
The impact-generated tsunami wave arrives approximately 34 minutes after impact.
Tsunami wave amplitude is between: 1.3 meters ( = 4.27 feet) and 66.5 meters ( = 218 feet).
My conclusion: I’m guessing the wide range of wave heights given is due to geographical factors like sea-floor depth. Since the Gulf coast is shallow, I’d bet the wave will be riding pretty high, but let’s take the average between 1.28 meters and 66.5 meters. That’s 33.89 meters, or about 10 stories.
As a matter of curiosity, would a 10 story wave knock over a skyscraper?
In Japan on March 11, 2011 a 60-foot wave knocked over 4-story concrete buildings.
http://www.oregonlive.com/today/index.ssf/2011/04/surveying_what_survived_the_quake_and_tsunami_--_and_what_didnt_oregonian_in_japan.html
60 feet is 18 meters. 18 meters is 5 stories. So a wave just 1 meter higher than the top of a building is all that it took to knock it down. I don’t think this scales up in a linear fashion. It really depends on how deep the foundations go, how wide they are, and how strong they are. I’m going to guess that a 10-story wave could knock over almost any building of between 10 and 30 floors, depending on the aforementioned factors. Think about it this way, if you were standing on the 15th floor of an apartment building that’s 30 floors high, watching a tsunami sweep by just 5 floors below you, do you think you’d survive? Would the building? My best guess is no and no. Yours probably is, too.
Final Conclusion
A missile weighing 10,000 kg moving at 30% the speed of light would be a local disaster. Lots of people would die, but it won’t be the end of civilization, or humanity, or really the end of anything on a global scale. It will, however, make even the biggest nuclear bombs look like firecrackers.
A special thanks to everyone who helped me with my research: Rudy Adkins, Tim Ross, Robert Weyer, Daniel Eloff, Gray Browne, Greg Kirkpatrick, Robert Weyer, Lyle Diediker, Joe Czolnik, Lloyd West, Henry Straley, Andrew Wilson, Cash Monet, John Treadwell, Jeff Morris, Dylan Dinh, Henry Espinoza.
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ABOUT THE AUTHOR
Jasper T. Scott Jasper Scott is the USA Today best-selling author of more than 13 novels written across various genres. He was born and raised in Canada by South African parents, with a British cultural heritage on his mother's side and German on his father's, to which he has now added Latin culture with his wonderful wife.
Jasper spent years living as a starving artist before finally quitting his various jobs to become a full-time writer. In his spare time he enjoys reading, traveling, going to the gym, and spending time with his family.