Tags: astronomy, survival
Yeah, we survived another near miss... near in the astronomical scheme of things.
If a 3,600-foot-long asteroid had hit Earth, it would have had the effect of an X-kiloton nuclear bomb. I don't know the number, sorry. I tried to look it up, and I did find some discussion of how we could use a nuclear bomb to destroy an asteroid that really was about to hit us:
With only weeks' notice, we would have to hastily come up with a plan.... If we blow up an asteroid that is too close to Earth, the end result could be just as catastrophic—a "shotgun effect" that could rain down fiery fragments of debris over a huge portion of the Earth.... And then we need to know what the asteroid is made of. Whether we would try to hit it with a spacecraft, divert it with a nuclear blast, or completely destroy it with a nuke depends significantly on what the asteroid is composed of, whether it's light, porous silicates or dense iron-nickel alloys known as meteoritic iron.... Another problem is that the fusing mechanism of a nuclear device would be destroyed in an impact over 671 miles per hour effectively disarming the nuke...
पोस्ट्स
३४ टिप्पण्या:
Bruce Willis, call your office.
"With only weeks' notice," of an asteroid big enough to destroy us the only option would to be to kiss our ass good-bye. However, 6.8M miles isn't really very close, even "astronomically" speaking.
On the up side, any survivors would be preparing very authentic meals for a long time after a big asteroid strike.
Imagine what it would/will be like when we learn society has 6 weeks to live. For one thing, I suspect everybody will stop working, Food and fuel will be unavailable.
It would sorta be necessary to land on the large body with the device to avoid destroying the fuzing
Shows why Comet Guy was way more important than his shirt.
The theater where we saw Star Wars ha 45
Minutes of coming attractions and in every one of them the world ends in catastophe. That attracts people these days.
Go Asteroids.
"Yeah, we survived another near miss... near in the astronomical scheme of things."
The frontal area of the Earth is only about one four millionth the size of the area given by a 6.8 million mile radius. On the other hand, the one that blew up over Russia a couple of years ago was only 17 meters in diameter and had an estimated energy of 470 kilotons.
Bob Boyd said:
"On the up side, any survivors would be preparing very authentic meals for a long time after a big asteroid strike."
Considering all of the fires that would be set off after a massive asteroid strike, they would be authentically burnt meals, too.
Another problem is that the fusing mechanism of a nuclear device would be destroyed in an impact over 671 miles per hour effectively disarming the nuke...
that is about the speed of sound. Our ICBM's manage to fuse properly flying at 25,000 miles an hour.
Star of wonder, star of light.
"... the fusing mechanism of a nuclear device would be destroyed in an impact over 671 miles per hour effectively disarming the nuke..." I'm pretty sure that the warhead of the average intercontinental ballistic missile arrives on target at something over 700 miles per hour, so this would seem to be a solvable problem. Not to mention that class of nukes designed to penetrate the ground be exploding. The writer of the article seems not to actually know much about nuclear weapons.
Would you really want to hit the asteroid head on to try to shatter it? Or would you rather have the nuke go off near it and to the side, so as to alter its orbit and have it bypass earth?
The longer the warning time, the less you need to do to divert it (assuming your calculations regarding the path of the object are accurate). With years of lead time, people have proposed simply parking a reasonably massive spacecraft next to the object. The gravitational pull of the spacecraft (or the change in curvature of spacetime, more properly) will divert the object by a tiny amount. It's sort of like the power of compound interest.
Not just a big impact on earth, what happens on Earth if the Moon gets hit big? Yes, I just began Neal Stephenson's Seveneves.
What you have to do, see, is land a spacecraft on the asteroid, with a weird, gravity-defying oil-rig spacetruck on board. Make that two; take two of them up there. Then you drive over, drill a hole, set off the nuke, and Bob's your uncle. Not a big deal.
I won't even speculate on how bad it would be if it were a Muslim asteroid and it struck the earth. Except to say that, if Donald were prez, it wouldn't get past INS. No frikkin' way.
Crimso said...
The longer the warning time, the less you need to do to divert it (assuming your calculations regarding the path of the object are accurate). With years of lead time, people have proposed simply parking a reasonably massive spacecraft next to the object. The gravitational pull of the spacecraft (or the change in curvature of spacetime, more properly) will divert the object by a tiny amount. It's sort of like the power of compound interest.
I've heard that story too, but it doesn't make any sense with the physics I took. The only way to "park" a satellite near the asteroid would be to orbit it. The center of mass of the two objects (essentially indistinguishable from the rock itself) would continue on it's merry way to a collision (there would be a minor perturbation of the orbit with the process of getting into orbit, but since you think it's going to take a while to move it, that can't be it). If you set the satellite to one side, and continued to apply thrust to keep them apart, that would do it, presumably, but then why not just land the satellite, point it's thrusters up and use it that way? You could even make the satellite dig up some material and throw it with a rail gun using electricity from solar cells, and save yourself the trouble of bringing the fuel for rockets.
Big Mike said...
"Would you really want to hit the asteroid head on to try to shatter it? Or would you rather have the nuke go off near it and to the side, so as to alter its orbit and have it bypass earth?"
I like it. In the movie, have the genius devout Muslim electronics expert come up with the idea because he is smarter than all the white guys. Best Supporting Actor.
Don't worry, SMOD will be here soon enough... http://www.nationalreview.com/article/428968/2015-review-smod-presidential-endorsement
"If you set the satellite to one side, and continued to apply thrust to keep them apart, that would do it, presumably, but then why not just land the satellite, point it's thrusters up and use it that way?"
Because it's easier and more controllable to just put it in orbit. Even guys in really cool shirts can't reliably land on an asteroid.
"If you set the satellite to one side, and continued to apply thrust to keep them apart, that would do it, presumably, but then why not just land the satellite, point it's thrusters up and use it that way?"
Additionally, the asteroid will have some rotation, which if you're on the surface would be a nightmare to compensate for. Put a satellite in orbit and the problem doesn't even arise.
The idea that you would a contact fuze on a nuke is just plain silly.
Abdul Abulbul Amir, may his tribe increase, captures my thought exactly. Air burst it (or in this case, space). Use radar to cause it to function before contact.
Regards — Cliff
The asteroid that wiped out the dinosaurs 65 million years ago was about 10 km in diameter.
The blast is estimated to have had a yield of about 100 million megatons. That is equal to about a thousand global thermonuclear wars.
You would NOT want to blow up the asteroid, because the pieces would rain down on Earth, many of which would be too big to burn up in the atmosphere.
The right answer is to deflect it by landing restartable rocket engines on it, then firing those engines so the rocket exhaust changes the trajectory just enough to miss the Earth. That would require much more advance notice, of course.
"The right answer is to deflect it by landing restartable rocket engines on it, ..."
Sigh {shakes head}.
"Ha ha you missed me!" isn't really a sound strategy.
Believe it or not, NASA and the military have looked into this. Not an easy problem to solve. Worst case is an oort cloud comet on a collision course with Earth. Oort cloud comets can come from any part of the sky, they have orbits that are unpredictable until they get close to the sun (they lose lots of mass), and they are big and they are fast.
Fortunately they aren't common. The 'appearing from any part of the sky' thing makes them less likely to strike the Earth.
If you divide the possible hits into city-killers, continent-killers, civilization-enders, and extinction events, the big problem, as far as public policy goes, is continent-killers. Suppose a big rock is on the way and we know it will hit the pacific basin. The Europeans and most of America will be okay. Suppose the Chinese say they can deflect it, just a little, enough to make it impact on land instead of the sea and save tens of millions of lives, but now the deflection will make it land in Europe or North America . . .
sinz52-
I've read that the reason the K-T extinction event caused forest fires world wide is that the release of energy caused all of the global upper atmosphere to glow as bright as the sun for about half a minute.
"The feminist movement died a millisecond after impact" - Lucifer's Hammer
sinz52: Has the yield of one thermonuclear war been calculated? I am wondering who the players might be.
BTW: I do tend to agree that the probable solution is two identical recently invented space ships traveling right next to each other, and refueling at an old Russian space station, with super drill rigs, decent bombs, and a hand held detonation kit for just in case.
I've read that the reason the K-T extinction event caused forest fires world wide is that the release of energy caused all of the global upper atmosphere to glow as bright as the sun for about half a minute.
The kinetic energy of a colliding bolide is going to absorbed by the Earth no mater what. It's going to be either a direct transference into the crust, i.e. a big crater with a small proportion of the total energy translated into heat, e.g. the K-T impactor, or it's going to be entirely thermal energy transferred to the atmosphere with little or no cratering, e.g. the Tunguska Event of 1908, or some combination of the two. The Chelyabinsk meteor shows that even a small fireball can produce a lot of damage through its shockwave alone. If the K-T impactor had been an equivalent mass of millions of small chunks the destructive effect on the Earth would have be considerably greater than the actual impact. Astrophysicists have crunched the numbers regarding collision scenarios dozens of times, and the consensus agree than if it's a choice between the blast-effect of a crater or atmospheric heating caused by thousands of small incandescent bodies, the crater scenario is less disastrous.
The upshot is pulverizing a collider with nukes, a plot point of many a sci-fi epic starring an action hero, is a very bad idea. However, this does not mean nukes have no utility in planetary defense. No, far from it. They are our only hope in the case of a collider that escapes early detection. A properly employed nuclear detonation can exert an acceleration on an asteroid or comet that must alter its orbit. The delta-v can be gentle or forceful depending on many controllable factors. The nuclear device itself can be very small so projecting it into a rendezvous flightpath should not be a problem in terms of an appropriate launch vehicle. The problem is the design of the device. The warheads we have on our ICBMs and in our the bombs are just not appropriate. If razing a city to the ground is your goal they're great, but nudging an asteroid in space? Not very efficient.
Warheads have been engineered for light weight and tremendous blast. To apply an acceleration to a body in space what you need is reaction mass, and our warheads just don't have much of that. For planetary defense what you need is essentially a nuclear shaped charge enclosing a dense material that can be ionized and propelled directionally so as to impinge the surface of the body to be accelerated. Tungsten has been proposed as a useful reaction mass. The nuclear explosive itself does't need to be huge, a few kilotons will be sufficient. (The US Army has designed dozens of tactical nukes in that yield range.) The shape, however is critical. If the troublesome bolide is a potato-oid, i.e. a solid mass shaped like a root vegetable, and has no particular weak point, then we want is a nuke with an enclosed disk-shaped reaction mass. This will produce a cigar-shaped plasma debris wave, which in turn will impinge on the target asteroid with high efficiency and high specific impulse. Comets on the other hand appear to be highly asymmetrical and rather fragile. A force that would merely nudge an asteroid might cause a comet to break apart, making things worse. In that case the embedded reaction mass should be cylindrical, which will create a more diffuse disk-shaped plasma wave, which will impinge the comet with a low specific impulse. Obviously an asteroid might be deflected by only a few high-impulse nuclear detonations, while a similarly massive comet might require dozens or hundreds of low-impulse shots.
Ahem. A "near miss" is a collision, actually.....
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