Posted on 11/17/2007 2:07:34 PM PST by blam
Deflected asteroids may keep coming back
17 November 2007
What goes around comes around. Unfortunately, no such karma figures in plans to deflect asteroids on a collision course with Earth, a hearing of the US House Science and Technology Committee was told last week. One big whack will deflect an asteroid temporarily, but does not guarantee safety next time its orbit brings it close.
Asteroid researchers have long debated the merits of deflecting asteroids with a powerful blast such as a nuclear explosion. However, Rusty Schweickart, who heads an asteroid research group called the B612 Foundation, told the committee that the effects of powerful blasts are hard to predict, especially if Earth's gravitational pull acts on the object. An asteroid could pass through one of the "keyholes" that would nudge it back onto a collision course, so once diverted it might need to be steered past Earth to prevent this.
(Excerpt) Read more at space.newscientist.com ...
An h-bomb’s destructive force on earth is dependent on atmospherics to conduct the concussive forces of the blast...the concussive shock and massive heating of the air do the most damage. Closer in, of course the heat and radiation does a lot of direct damage but with out atmosphere the damage radius is fairly limited.
So you have to bury the bomb in any large asteroid for it to do any good. Smaller asteroids or icy commets may be melted by a sufficiently close atomic release. Yet, in space an atomic flash would be brief and intense like a large flashbulb with a spherical out put levels of thermal and multispectral radiation which would decline with the square of the distance as the pulse expanded out ward.
And that is the problem...transporting a suitable bomb to a large asteroid, then getting it buried deep enough in a fissure that it would split the asteroid or shaping the charge so that a huge amount of ejecta is thrown out into space, the force of which acts as a chemical
rocket which alters the asteroids course.
That is why nukes are poo poohed. I think when it came to “saving the planet”, even the most PC types would “grudgingly” approve the use of nukes if the science supported their use.
Still, I’d bet desperate governments might still authorize nukes as a “hail Mary” last ditch effort to stop a mountain size asteroid from hitting the Earth
Most asteroids are spinning in three directions on their x,y,and z axis. Detirmining a “side” to push on would be hard to do as the asteroid is twisting and tumbling as your nukes are going off!
If it can be broke in 3 or even 2 pieces, the net energy in each part is going to be on a separate vector - diverging by definition - from the original course.
Why is impacting a nuke on the surface of an asteroid - regardless of position, rotation, axis, time, or depth - not 1000 times easier than trying to create an imaginary rocket/thruster,sail,ion jet or anything else that must be developed, built, flown to the intercept, maneuvered into place remotely - with a 8-15 minutes delay ?????? between signal and response - and somehow mounted exactly on the axis at the right azimuth to drive the asteroid?
We can’t even land satellites on Mars successfully in routine ops yet.
You’d have to deal with x, y, and z axis rotation(as in multi axis tumbling) as well so you’d have to think of two or three drives to allow for control of angular kinetics.
Above all, it looks like as a race we are going to have to hike up our britches and fully thrust our selves out into near space and interplanetary space to begin protect our selves and to harvest the bounties that are our there...I was born 46 years too late!
I agree. As a species we explore and do our best when we take on challenges. I want to see humankind moving through the solar system and out into the broader cosmos.
The old fire cracker anomaly...hold a fire cracker on its extreme end with just your finger nails and it will explode with little damage...grasp it with an enclosed fist and you run the risk of blowing off your fingers.
The concern is you do little damage and do little to change a large asteroid’s course by exploding it on its surface. With smaller asteroids and comets say small sledding hill size or less, you might melt a good part of it and the ejecta might change its momentum enough to miss earth on the first pass but larger asteroids are going to need something more drastic!
We need a giant Astromatic.
Call Ron Popeil.
It would be a rotating bank of large ginsu-type knives that would slice or dice, resulting in the the now smaller fragments vectoring off their original course and missing the Earth.
The thing is, nukes are all we have at this point in the short term to counter smaller threats say 500 feet or less as close up nuclear releases might simply melt them into vapor. You are talking about an instantaneous temp of greater than 100 million degrees centigrade(higher for h- bombs) and a smaller object’s elements might literally catch fire even with out oxygen(causing secondary high temp chemical reactions) if the object was sufficiently was close enough to the nuke.
A 1000 foot to 2000(6300’ circumference) foot object might be lit for a short time on one end like a candle and hopefully change the object’s direction if you caught the object far enough out sufficiently. The key there is if you had sufficient warning, time for prep, and could catch the object far enough out!
The real bad scenario would be a mile wide asteroid or more spotted less than 6 months, perhaps as little as a month or sooner out of its collision point with Earth. Depending on its composition a nuke would have little impact especially iron/nickle core objects.
A mixture of frozen water/ methane and rock/metal might be dealt with successfully as the nuke’s instant high heat at an impact or near impact explosion point would vaporize the elements with oxygen being stipped from hydrogen because of the super thermal heat...one could see a series of secondary explsions and chemical reactions until they gave out due to the remaining bulk of a super cold asteroid/comet.
If a shaped nuclear charge could be introduced into the body of a icy comet/asteroid, then the ejecta could thrown out in a more funneled/tuned fashion like a jet flame which, if far enough out would definitely change the direction/speed of the object so that it would miss earth.
The point is we would dependant at this point of the heat/radiation of the nuke to do any thing useful as atmospherics wouldn’t be available for concussive factors. The flash of the nuke is only for an instant in space so it would have to be in contact or very close vicinity to do anything reasonable.
Now, one could conceive in the next 30 to fifty years if we could get enough international cooperation, in building a more robust planetary defense. There is no atmosphere in space for nukes to do much good on large mile wide or more objects...but what if a good 100 mega ton nuke could take some atmosphere with it? A series of interplanetary grenades(a mile in diameter or less depending on the job you needed it for) if you will, with a heavy iron/nickel lead base topped with a sturdy shell that was studded with large rock or metal projectiles...this shell would be designed to fracture in key places. In side of this shell would be highly compressed or frozen oxygen and hydrogen or filled with highly oxygenated,dueterium/tritium laden water. At the center of it would lay your nuclear device. These devices could be kept at various lagrange points between Earth and moon or even between Earth or sun or various planets and the sun. If an object was spotted coming at Earth, say a 1000 foot diameter(3149’ circumference)...a juniour sized grenade say 100’ or two with an appropriate sized nuke could be launched out to meet it, using planetary gravity assist to help sling shot it to at least 20 to 30 miles a second. The idea of the bomb would be to amplify the effect of the nuke by creating a 1-2 kinetic plus heat effect weapon. The heavey iron metal base would survive long enough to shape the charge of the explosion forward, the forward velocity of the weapon cancels out reverse action of the explosion. The outer shell would fracture forward at high velocity propelling the iron/stone objects into the asteroid helping shread it...especially if the asteroid were of mixed consistency or loose objects. Then of course there is the matter of a nuke being exploded with tons of water or liquid hydrogen and oxygen surrounding it all of it suddenly flashing into a shaped superheated plasma crashing into an oncoming asteroid. If the nukes were set in a deuterium/tritium heavily enhanced water shell with a relatively compressed air/water shell around that, the resulting explosion and aftermath would probably be visible at least through telescopes from millions of miles away. The technology is feasable and most of it would be off the shelf albeit expensive. We would have decide as a world to put our differences aside and decide to lauch into space in a big way in order to put such a system into operation
Make a few assumptions (months to impact/intersection; mass of incoming object; number of km it needs to move to miss (number of degrees of deflection).
Figure out what impact/impulse is needed to create that much movement.
Use a chemical rocket? Probably can’t get that much mass that far out and still keep accelerating it: the Apollo program (and we have no large rockets now!) could only get a little bitty command capsule and LEM + eqpt module to the moon - and that by coasting (not accelerating!) .
But, that creates a starting point for discussion.
Well in a way yes....large 100 foot to 5000 foot diameter guided interplanetary grenades with a heavy nickel/iron base with a pre-stressed metal half dome shell on top.
An appropriate nuke lies inside which is surrounded by an explosion enhancing heavy water shell inside a layer of compressed air or liquid hydrogen and oxygen. The outer shell is studded with heavy rock or metal fragments and the shell itself is prestressed so that it fractures forward under tremendous pressure from the nuke created steam/superheated plasma mix behind it. In a sense a grenade that superheats as well as slices and dices.
What doesn’t get shredded gets melted and even if the object isn’t totaly destroyed...you can bet its direction gets changed especially when far enough out from Earth. The metal base of the grenade if designed right should last long enough to shape the explosion forward.(forward velocity at 20 miles a second should cancel out the reverse effect of the explosion allowing the explosion to be shaped forward) The trick is to find the optimum explosion point, even impact might do major direction change/damage with all that gas/steam/ superheated plasma being released!
Lets start with twelve months and we know a thousand foot(3140’ circumference) asteroid has a 99 percent probability of hitting Earth. Its a mixed class got a heavey iron/rock core and some dirty icy water and frozen methane on it. It’s mass would be that of say a couple of super aircraft carriers appox 200000 tons.
Because it is coming in towards the sun and us it is actually accelerating so that when it reaches us it will be traveling at roughly 10 miles a second and it is currently 310 million mile from us leaving roughly a year.
So we need to know at what point to do we need to know when an asteroid is going to hit us so that we can meet it a 6 months to a year out so that we can make use of its slower velocity farther out so that the feeble forces we do have can make the most good....lets say 1 year out.
Now this is where my astro-physics fails me since I don’t know the gravitational accelration constant of the sun. I know on earth its roughly 9.75 meters per second squared and I’ve read that most object hit the earth between 7 to 20 miles a second depending on direction and other factors. My reading suggests that such an object hitting our earth at 36000 miles per hour would strike us with a 500 megaton eqivalent of energy released, a real killer.
So the parameters are to strike or effect the asteroid at 310 million miles out while the object is traveling at about 7 miles a second but accellerating as it comes toward the sun. We would have to affect it enough so that it did not strike us on its way about the sun and on its return outward again. We would need it to miss us by 30000 miles so as to not affect our geo-synchronous satelites. We know also is that its got movement along it three axis(tumbling slowly)!
It would depend on the proportion of energy carried away from the blast as kinetic energy of material vs. electromagnetic. I would think that such a bomb would be designed to yield a barrage of high speed matter impinging on the asteroid, a shaped charge of lead or depleted uranium to the asteroid side. I’m confident that we would not send a neutron bomb to do the job.
A nuclear blast contains lots of high speed matter blasting out of the center as well as EM energy. A properly built bomb would have a shell of matter to achieve its purpose, converting and conveying mass impact (KE) to the target.
You know of course that I am not criticizing you personally when I say that there have been like what, 50 billion people who have lived and died on this planet and NOT woke up every morning wondering if the asteroid they just deflected is gonna come back?
So excuse me if I sharpen my spear because odds are today I will get that nasty mastodon that keeps eatin my roses. (Unless I get smashed by an asteroid)!!
LOL!
We should go to the asteroid belt and kill them all before they attack us at home!
My “grenade” is designed to have such heavy shrapnel thrown out a head of it with a heavy push of super heated steam/gas/plasma behind that..
The idea is to send a nuke with atmosphere/compressed gas or water all incased in a shell. The nuke goes off sending shrapnel ahead of it followed by a “push” of superheated gases that provide anough energy to push a fairly large asteroid off its collision trajectory. Smaller asteroids, especially those of ice and rock variety or comets might well be obliterated.
The talk has been why the experts won’t consider nukes against asteroids; nukes by themselves are just a quick flash heat, light and radiation and aren’t useful against really large asteroids...especially iron/nickel/rock types.
But send out a nuke(a 100 megaton minimum) incased in water/compressed gas or other combination...enhanced with heavy water dueterium/tritium all encased in anouter shell of metal/rock and then you’ll get a weapon that will well be effective. The technology is well within our capabilities...just massive in scale and there-fore expensive. The question is are the risks for asteroid collision large enough justify the costs of building such systems? These systems would be large anywhere from 300 feet to 10000 feet in circumference depending on the size of asteroid and the distance/time factors in volved in meeting the asteroid far enough out to do any good.
They would have to be pre-positioned in space in various La Grange points and in the short term chemically powered to begin to accelerate them toward their targets using gravity sling shot planetary assist where possible. Ion engines have been tested and could after a few months of gentle acceration propel a weapon to almost relativistic speeds 100’s miles a second but the difficulty is providing the power and drive mass to keep the engines running unmanned.
Ultimately how many would we need?... Tunguska type impacts happen once a century. Smaller objects have put holes in roofs of houses, but surely the cost analysis would preclude defending against those. Extinction level events happen evey 50 million years or so, regional or continental devestation events happen perhaps sooner.
The only real option is that this world finds a way to settle its internal squabbles and learn how to launch into space in a big way, finding new raw resources ...”out there”! Once there we would have a better handle as to the bigger threats that face our Earth and what we would need to do to prepare for them!
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