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No Bomb Powerful Enough To Destroy an On-Rushing Asteroid, Sorry Bruce Willis
coondoggie writes "Maybe it's the doom predictions about the end of the Mayan calendar this year, or maybe these guys are obsessed with old Bruce Willis movies. Either way a class of physics students from the University of Leicester decided to evaluate whether or not the premise of Willis' 1998 'Armageddon' movie — where a group of oil drillers is sent by NASA to detonate nuclear devices on an asteroid that threatens to destroy Earth — could actually happen. The students found it would take a bomb about a billion times stronger than the biggest bomb ever detonated on Earth."
Armagedon is not that old at all.. uhmm.. ohmm...
Fuck, get of my lawn
We have a bomb that big! OoooOOOOOooh!
is it me or did the class get it wrong, it was never about destroying an asteroid, it was about splitting it up in pieces or nudging it out of the earth direction
The students devised a formula to find the total amount of kinetic energy needed in relation to the volume of the asteroid pieces, their density, the clearance radius (which was taken as the radius of Earth plus 400 miles), the asteroid's pre-detonation velocity, and its distance from Earth at the point of detonation. Using the measurements and properties of the asteroid as stated in the film, the formula revealed that 800 trillion terajoules of energy would be required to split the asteroid in two with both pieces clearing the planet. However, the total energy output of Big Ivan "only comes to 418,000 terajoules. The asteroid is approximated as a spherical object 1000km in diameter
"First they came for the slanderers and i said nothing."
The biggest one ever detonated, the so called "Tsar Bomba", was 50 megatons of TNT. It could have been made 100 MT, but was scaled back to reduce fallout, and was therefore a very clean bomb for its size.
There was however no point in building bombs of this size, so no one has attempted it since, opting instead for clusters of smaller bombs to carpet an area or using modern targeting to accurately take out small targets with great precision,
Bombs that big where shere lunacy and just a demonstration of power.
This is the real paper, coming in at only 2 pages it's a light read: https://physics.le.ac.uk/journals/index.php/pst/article/viewFile/390/243
You weren't going to RTFA anyway, now were you?..
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P1_1 Could Bruce Willis Save the World?
Back A, Brown G, Hall B and Turner S
Department of Physics and Astronomy, University of Leicester, Leicester, LE1 7RH.
November 1st, 2011
Abstract
The film Armageddon (1998) puts forward the possibility of using a nuclear weapon buried deep within an Earth-bound asteroid to split the asteroid in two, each half clearing opposite sides of the Earth with only relatively minor damage. This article investigates the feasibility of such a plan and shows that even using the largest nuclear weapon made to date, the bomb comes over 9 orders of magnitude short of the yield required.
[...]
Actually, there was a real, sensible (as things go in the field of nuclear deterrent) reason for them: The USSR did not at the time have anything that could deliver a payload with precision. Plus, they used big and slow bombers, which made it possible to intercept them. Thus, they employed a lesson from Ken Thompson in the future: "When in doubt, use brute force". :)
The design was not scaled down as such - it was a 100MT bomb; they simply substituted lead for U-238 in the tamper.
toresbe
Very doubtful. But we could potentially build such a bomb if the Earth depended on it for some reason; the Teller-Ulam configuration scales indefinitely. The problem is it'd be way too massive to get off the ground.
Of course, these students were simply calculating the (very unrealistic) scenario found in the movie, of the asteroid right about to impact, and of deflection involving splitting it in half and having one half go each way around the Earth. As they note, more realistic deflection scenarios involve hitting it much earlier and simply trying to alter it's trajectory intact (but that's not fitting for Hollywood)
Also it should be noted that the Tsar Bomba mentioned in the article was deliberately cut down to half of its design yield (replacing the uranium tamper with a lead one) to make it burn cleaner. It was not only the biggest atomic bomb ever detonated on Earth, but also the cleanest per unit of energy output.
Sometimes I doubt your commitment to Sparkle Motion.
Even worse: There are no asteroids with a diameter of 1000km. The largest of them, Ceres, is 950km and at a very safe distance in a very stable orbit. The second largest, Vesta, is less than 600km in diameter.
In fact, the main "danger" nowadays is seen in objects of about 0.1km in diameter, since that is the size at which asteroids are still damaging, but also escape early detection. That takes about 15 orders of magnitude off the energy requirements. But at this point, you wouldn't even need a bomb. Just shoving a few tons of stuff at a few km/s in front of the asteroid is enough to tear it apart. (The kinetic energy of 1t of material at 2.8km/s is equivalent to 1t of TNT.)