David S.F. Portree hosts the 54th Carnival of Space at his Altair VI site this week. I love Altair VI — the stories are consistently interesting and the artwork well chosen as well as frequently unusual. Besides, a collector of old pulp magazines like myself can’t help but be drawn to a site with an early 30’s era Science Wonder Stories cover at the top. From this week’s carnival, I’ll send you to Starts with a Bang!, which looks at what we could do to nudge an asteroid away from a potential collision with Earth. Noting that 433 Eros, which came near Earth recently, sports a mass of 6 x 1015 kg, Ethan Siegel flags the thermonuclear option as the best bet for moving such a massive object, assuming we get two months’ warning.
Of course, two months’ warning depends upon how well we’ve mapped Earth-crossing objects, an inventory still being built. Let’s hope this century will see us create the infrastructure to nudge these things out of harm’s way via missiles from launching sites at the LaGrange points, a la Claudio Maccone’s concept. For more, see the Italian scientist’s two part study “Planetary Defense From Space: Part 1-Keplerian Theory,” Acta Astronautica Vol. 55, Issue 12 (December, 2004), pp. 991-1006 and “Planetary Defense from Space: Part 2 – (Simple) Asteroid Deflection Law,” Acta Astronautica Vol. 58, Issue 12 (June, 2006), pp. 662-670.
Thanks for noticing my article! It’s incredibly exciting stuff, but it turns out that no matter how you do your calculations, the way to deflect an asteroid using the least amount of total energy is to either ram it or jolt it or make an explosion close to it as soon as possible. The longer you wait, the more energy you need to expend to deflect it.
Hi Paul;
One possible way to nudge a 6 x 10 EXP 12 metric ton asteroid off course is to use a stand off blast from a 12 Gigaton thermonuclear device or perhaps such a device in the form of a neutron bomb with the same yield perhaps in a directed energy type fashion. Assuming that 1/2 the energy yield of the device could be imparted to the asteroid material. The velocity change in the asteroid would be about 100 meters per second. This velocity will allow course correction or deflection of about 3.1 million kilometers in one year or roughly 310,000 kilometers in month.
A standoff neutron bomb blast of this yield would allow ionizing radiation to penetrate several meters into the asteroid thereby vaporizing a thick surface layer which would then give the asteroid a huge push as the billions of tons of asteroid material converted into gas/plasma push against the asteroid as the gas is blasted away from the asteroid.
Such a device would be very massive however, but at 225 megatons per metric ton of fully fused fussile fuel, in theory, only 50 metric tons of fusion fuel would be needed for the bomb. If half of the fuel could be made to fuse while the other half would perhaps unfortunately be blasted away in the explosion of the device’s primary before it fused, then a device with a mass of about 100 metric tons might do the job. This device could be lofted into Low Earth Orbit by the Ares IV rocket being designed for NASA’s CEV meant to return humans to the moon.
Thanks;
Jim
Nice. But the calculations are just overly optimistic to say the least…
True – it may be possible to construct multi-stage thermonuclear warhead with a 100 Mt-yield weighing 20 tonnes – the Tsar Bomba weighed 27 tonnes and could have achieved this.
What is completely impossible is transferring whole 50% of it into the change of kinetic energy of the asteroid. Taking into account the conservation of momentum, one would have to use the remaining 50% of the energy on moving the exact mass of the asteroid in the opposite direction with exact speed. I.e. to literally splitting the asteroid in two. Then, if the velocity difference between them is only 5 mph, they would simply rejoin…
I’m glad that asteroid deflection is given the attention it’s due finally, and after reading his post I agree that the chance of blowing the damn thing into thousands of pieces is better than a ‘for certain extinction level event’.
This is a far nobler use for thermonuclear weapons than at present.
Arthur C. Clarke would’ve approved.
Where is there a good write up predicting when we’ll know the orbits of nearly all of the Earth-crossing asteroids by size? It seems to me that at our accelerating ability to detect smaller and smaller asteroids that the time will come when we’ll have years advance notice of nearly all asteroids with the potential of significant destruction. It appears to me that the various sky surveying programs may be approaching the point where the discovery of civilization-destroying asteroids is nearing its conclusion. I would be inclined to put our money and effort first into discovering the threats since we’re making pretty good progress. Then, as we discover an asteroid that we know is coming our way, we will have a timeframe for the development of a deflection mission.
The Sky Is Falling
The Atlantic June 2008
*************************
The odds that a potentially
devastating space rock will hit
Earth this century may be as high as
one in 10. So why isn’t NASA trying
harder to prevent catastrophe? We
will soon have a new president, and
thus an opportunity to reassess
NASA’s priorities. Whoever takes
office will decide whether the
nation commits to spending hundreds
of billions…
http://www.kurzweilai.net/email/newsRedirect.html?newsID=8692&m=25748
Hi Michal Barcikowski;
Thanks for the clarification regarding momentum transfer to the satellite from an outside detonation. For some dumb reason, I overlooked that simple kinematics consideration you brought forth in your above posting.
One might however increase the yield of the nuke or use several large nukes simultaneously or sequentially to nudge the asteroid out of the way.
I can imagine assembling a huge water bomb safely away from low Earth orbit composed of one million metric tons of water which would be set of as nuclear fusion fuel by a very high mass specific power primary nuclear device or perhaps a shaped charge nuclear device for which open literature suggests could produce a explosive energy flux concentration as much as 6 orders of magnitude greater than that possible with a typical sized spherically symmetrically exploding nuclear device.
A million ton water bomb that undergoes full water fuel i.e. oxygen or oxygen and hydrogen fusion would yield roughly (2 X 10 EXP 2)(10 EXP 6)(10 EXP 6) tons of TNT or 200 Teratons of TNT. If only 1/10 of this energy release went into a typical iron silicate rock asteroid’s material, in theory an asteroid with a mass of about 20 Teratons could be completely vaporized. A 2 billion ton water bomb could vaporize completely a 100 quadrillion metric ton or 10 EXP 17 metric ton asteroid if 1/4 of its yield was deposited into the asteroid’s material. Perhaps one could use carbon as a fusion fuel or some sort of super strong high elastic modulus material made from low atomic number elements such as polyester, Nylon, Kevlar and the like in order to provide nanosecond scale mechanical resistance to the explosive energy of the primary in order to provide the necessary pressures and temperatures to initiate a self propagating fusion wave though the fussile fuel.
There seems to be no limit to how big one could build a thermonuclear device given enough money, time, and resources. Oddly enough, that dreaded technology of the Cold War might end up being our best ally.
Thanks;
Jim
An Asteroid Deflection Research Center (ADRC) has been established
on the Iowa State campus to bring researchers from around the world
to develop asteroid deflection technologies. The center was signed into
effect in April by the Office of the Executive Vice President and Provost.
“In the early 1990s, scientists around the world initiated studies to
assess and devise methods to prevent near-Earth objects from striking Earth,” said Bong Wie, the Vance D. Coffman Chair Professor in
Aerospace Engineering and director of the center.
“However, it is now 2008, and there is no consensus on how to
reliably deflect them in a timely manner,” he noted.
Full article here:
http://www.scienceblog.com/cms/seeking-answers-asteroid-deflection-16559.html
Find out what it takes to wipe Great Britain off the map
with a space rock:
http://down2earth.eu/impact_calculator/