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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.
I always though the goal of the blast was not to destroy the asteroid but to change its trajectory...
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"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.
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You know nothing about physics. Kill yourself.
The uneducated only become educated through the sharing of knowledge, asshole. I'm certain there are things you know nothing about (it's called being human), and yet I'm not condemning you to death for it.
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.
If an asteroid is not rotating, it makes sense that if fractured into pieces by a thermonuclear explosion, the pieces will tend to drift back together in one place.
So our strategy for an Earth-impacting asteroid should be: if it is rotating, blow it apart and watxch the pieces fly away; if it is not rotating, nudge its orbit with a series of small explosions.
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.
Nobody wants to deflect an asteroid with another one. That would be stupid. Instead of getting 10000 tons on our head in 1 piece it would just come down in several.
Landing a drive on the sucker is easier, if it far enough out there.
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.
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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.
The problem is that impact doesn't scale linearly with size - the size of the crater scales with the cube-root of the blast energy - in this case the mass, since we won't be appreciably modifying the impact speed. Break an asteroid into 8 chunks, and now you have 8 impacts, each still having half the blast radius of the original. 64 chunks would each have a blast radius 1/4 the size of the original.
And while we may not be able to accurately predict the impact point months or years in advance, it gets easier the closer the impact point becomes. It also becomes easier the larger the asteroid is, so that solar pressure, etc. have less effect on its path. Weeks away we'd know roughly where it will hit, so everybody can get ready in case they have to evacuate, and we'd have at least days to evacuate a particular city - which should be quite doable with the amount of warning possible.
Ironically enough, an ocean impact by a large meteor is probably the worst-case scenario - at orbital speeds water is only marginally less solid than rock. The tsunamis created by the blast of vaporized water would likely be more devastating than a direct land impact, and all that water in the atmosphere would wreak havoc with global weather patterns - flooding, dense cloud-cover, etc., which could devastate global food production.
--- 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.
The answer is ablation.. You're going to flash-boil some rock, which is going to expand against the main body, and create thrust as it leaves in the other direction at a very good clip.
As for wasting energy from the blast into space, there are approaches to mitigating that, which go all the way back to Project Orion.
Finally somebody with some sense of physics! No, we never want to try to fracture an asteroid.
Straight ablation across one hemisphere seems like the best idea and change the orbit. Use something like the huge Spartan warhead encased in gold (for maximum x-ray creation). This was already created to heat and fracture the high Z atoms in enemy warheads and should work OK on a nickel-iron asteroid.
Best scenario would be to have years of warning, and land powered ion engines which could be controlled and changes accurately measured so no risky shots with unclear geological effect need to be taken.
>Fortunately, there's also this 1360 W/m^2 light flux near 1 AU making things significantly easier for us.
Which is only useful if we are between the asteroid and the sun. That's my point. My shining a flashlight towards you doesn't help you see anything between us, except in silhouette. And there's no background in space for a silhouette to be visible against.
Worse, we're not actually looking. Current astronomy amounts to a few hundred people looking through drinking straws at the sky - the vast majority of the sky never gets looked at for long enough to spot any particular asteroid, even if it's perfectly visible in theory.
Plus, near-Earth asteroids are the most persistent threat - and they spend their entire orbital path quite near Earth's orbit, mostly locked into a 1:1 orbital resonance with Earth. Which means they're basically invisible from Earth, except when we happen to be inside their orbit near their closest approach. Any other time, they're lit from the wrong direction to be visible. And Lagrangian orbits tend to be chaotic strange-attractor type paths when viewed from the non-reference point of the planet they're locked in resonance with - there's no guarantee that they'd get anywhere close to Earth, and thus become visible, before they're on a path for collision. And a relatively minor collision or gravitational deflection at the wrong time could deflect an asteroid from a previously stable orbit onto an Earth-colliding path.
It's not that they're hard to see - they're just hard to see *from here*. One of the proposals (several, probably), is to put asteroid spotting space-telescope(s) in a solar orbit inside our own, looking outward, so that they'll circle the sun independently from us, and every time they lap us around the sun, they will have had a chance to photograph the entire near-Earth asteroid belt in full sunlight. That, and some good software to spot the asteroids amongst the camera noise, and we could actually be fairly confident we spotted everything big (at least that's not extremely dark-colored). That strategy also has the benefit that the telescope stays very close (relatively) to what it's photographing, making it much easier to spot smaller still-dangerous asteroids.
--- Most topics have many sides worth arguing, allow me to take one opposite you.