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Deflecting an Asteroid Will Be Harder Than Scientists Thought (upi.com)
schwit1 shares a report from UPI: According to new asteroid collision models designed by scientists at Johns Hopkins University, deflecting a large rock headed for Earth will be harder than previously thought. Using the most up-to-date findings on rock fracturing, researchers developed computer models to more accurately simulate asteroid collisions. For the newest study, scientists decided to divide the model into two phases. Phase one modeled the immediate fracturing that happens in the wake of a collision -- the processes that play in a matter of seconds. The second phase simulated the gravitational re-accumulation process that happens over the course of several hours or days.
The first phase of the updated model showed a large asteroid is not destroyed by a much smaller asteroid. Instead, millions of cracks form throughout, the core fractures and a crater is left behind. During phase two, the fractured core exerts a strong gravitational pull on the smaller pieces of debris and shrapnel broken during the impact. Because the asteroid did not crack completely during phase one, the space rock retained significant strength. If scientists are going to develop an asteroid deflection strategy that can actually work, they need to know how much force it really takes to destroy or deflect one. The latest study -- published in the newest issue of the journal Icarus -- showed it's more force than was originally thought.
The first phase of the updated model showed a large asteroid is not destroyed by a much smaller asteroid. Instead, millions of cracks form throughout, the core fractures and a crater is left behind. During phase two, the fractured core exerts a strong gravitational pull on the smaller pieces of debris and shrapnel broken during the impact. Because the asteroid did not crack completely during phase one, the space rock retained significant strength. If scientists are going to develop an asteroid deflection strategy that can actually work, they need to know how much force it really takes to destroy or deflect one. The latest study -- published in the newest issue of the journal Icarus -- showed it's more force than was originally thought.
"Deflecting" and "destroying" are two different strategies to avoid collision with an asteroid - and "destroying" has long been seen as the worse one for that matter.
Of course news about a fake are Fake News.
The difference is that the birdshot has a better chance to burn up in the atmosphere without anything reaching the ground at all.
We used to have a Bill of Rights. Now, with the rights gone, all we have left is the bill.
If a large asteroid on a collision course with Earth is fractured, that just turns it into a bunch of little asteroids that will hit Earth.
Not really. Space is big. Really big. If you break up an asteroid months, or even weeks, ahead of time, most of the fragments are going to miss earth by many thousands or even millions of kilometers.
A typical delta-v is 40,000 km/hr. So in a day, that is a million kilometers. In a month, it is 30 million km. The diameter of the earth is 12,000 km. That is about 0.02 degrees. That is not much of a deflection.
I reckon $5 billion would be more than enough, and we'll get the Mexicans to pay for it.
Those who do not learn from commit history are doomed to regress it.
https://hub.jhu.edu/2019/03/04...
Looks like the editors did not even look at it and just "aggregated" the content from some random news site that also was no capable of summarizing the hart of the matter in a subject line.
There have been many, very useful analyses of the trade-offs. I've seen many in fiction and science speculative scientific analyses: I remember reading J. E. Enever's analysis in a 1966 Analog magazine article. Given how little was known about the composition of asteroids that had never struck the Earth to be analyzed, and that the article predated the discovery of the dinosaur killer asteroid, it was quite good. Asteroids are high velocity projectiles, and whether they are solid rock, reasonably metallic, or icy makes enormous difference in the results of breaking them up.
Orbital mechanics and basic geography physical chemistry haven't changed much since that period. Guidance systems have improved tremendously, and humanity has learned a great deal about sending small probes to other worlds. But changing the orbital path, or shattering, something as large as a dinosaur killer asteroid is still an incredible engineering problem.
"Ten days? Have a world-wide "End of the World" party." - Including watching the 1999 Canadian film "Last Night"... Plot: In Toronto, a group of friends and family prepare for the end of the world, expected at midnight as the result of a calamity that is not explained, but which has been expected for several months ... In 2014, Colin McNeil of Metro News wrote "Last Night is perhaps the most upbeat end-of-the-world movie you’ll ever see." ...
Rogert Ebert's review ... Note: On a talk show in Toronto, I [Roger Ebert] was asked to define the difference between American and Canadian films, and said I could not. Another guest was Wayne Clarkson, the former director of the Toronto Film Festival. He said he could, and cited this film. "Sandra Oh goes into a grocery story to find a bottle of wine for dinner," he said. "The store has been looted, but she finds two bottles still on the shelf. She takes them down, evaluates them, chooses one, and puts the other one politely back on the shelf. That's how you know it's a Canadian film."
Indeed. If it takes more force than originally estimated to fracture an asteroid, that's a *good* think - it makes deflecting it easier. Fracturing is one of the things most asteroid-avoidance plans want to avoid.
You only want to shatter it (and only maybe) if it's already too late to deflect it - doing so turns a rifle slug who's impact point we can predict, into a shotgun blast that'll hit all over the place, but probably some of it will miss, and more of it will burn up in the atmosphere so that individual impacts are less damaging. The overall effect is likely to be more devastating though - unless the original impact point would have been something especially bad.
--- Most topics have many sides worth arguing, allow me to take one opposite you.
Go take a look at the long list of asteroids that have passed frighteningly close to Earth, that we didn't see until they were already past.
The problem is that we have a 50/50 chance that the asteroid will approach us from inside our orbit, in which case the side facing us will not be lit by the sun, rendering it nearly invisible (though the IR telescopes designed specifically for spotting asteroids by their heat signature will do better)
--- Most topics have many sides worth arguing, allow me to take one opposite you.
Vaporizing is completely different than shattering. For starters, the remaining asteroid remains intact, while the vaporized rock leaves at high speed as jet engine exhaust. That works great.
Don't kid yourself that the size of the fireball has anything to do with the size of the crater it would produce though. The fireball is just superheated gas expanding through cool air, long after the blast has done its damage - it takes very little energy to produce compared to trying to vaporize or displace rock. Also, to get an appreciable crater you'd need to bury the nuke deep underground so that it blasts material upwards instead of down - similarly to how most of the energy of a meteor impact is delivered well below the surface as rock is vaporized out of its path.
And burying a nuke greatly increases the odds of shattering the asteroid rather than deflecting it. And that's almost certainly a bad thing. You've just turned a predictable rifle slug impact area that could be easily evacuated, into a shotgun blast.that will pepper the Earth with nuclear-size impact blasts. Even if half the material misses the Earth entirely, the total damage would be much greater - the size of an impact crater scales with the cube root of the impact energy (in this case, mass, since all else remains roughly constant). Break an asteroid into 8 equal pieces, and now you get 8 impact craters, each still half the diameter that the original would have been. Break it into 64 pieces, and each crater would still be 1/4 the size of the original. Even if half of them missed Earth, you'd still end up doing far more total damage.
About the only reason you'd want to risk doing that is if it was a *really* large asteroid that was going to hit the ocean, generating massive tsunamis and vaporizing a huge mass water that would devastate weather patterns for potentially years to come, doing far worse secondary damage.
And if the asteroid was that big, then even a Tsar Bomba buried in it's core might not be up to shattering it.
Plus there's the slight problem that unlike rockets capable of delivering it, we don't have any Tsar Bombas just lying around in storage (so far as I know), and building one is going to take time. time we wion't necessarily have, and even if we do, every second we wait to launch brings the asteroid closer and reduces the amount of benefit an explosion of a given size can achieve.
--- Most topics have many sides worth arguing, allow me to take one opposite you.
I'm trying to figure out what you might mean, given the fact that asteroids are typically invisible to radio telescopes, and the amount of radio power you'd need to broadcast to illuminate even a tiny sliver of the night sky brightly enough to spot an asteroid from half a billion km away would be mind-boggling.
--- Most topics have many sides worth arguing, allow me to take one opposite you.