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Subject: Rods From God
Vossiewulf    4/3/2004 9:58:48 PM
I haven't seen this discussed here, forgive me if it's a repeat. I sent a mail recently to the editor at G2mil.com, asking about kinetic weapons for bunker busting. I had been thinking about this for a while, having seen references to similar ideas in fiction. I couldn't understand why it wasn't being done, as it seemed like pretty simple technology. Take a tungsten or DU rod, say three meters long or so, put on some fins and actuators for guidance, and a GPS unit in the tail. Loft it up to low earth orbit, and when you want to make something go away, drop a big dart on them. If we're talking a deep bunker target, the question wouldn't be whether it was destroyed, but rather how much was converted to plasma and how much was reduced to fine powder. Not to mention that you might strike oil in the process. Someone with knowledge of the math could do the exact calculations, but I think it's safe to say that the KE and penetration would fall in the "Holy Jesus" category. It really could be dirt-simple tech. You have the cost to loft it upstairs, and its carrier has to be able to project it onto a vector, but that's it. Anyway, editor came back and surprised me by saying yeah, it's a good idea, and folks are already working on it. They call them "Rods From God". See: http://www.post-gazette.com/pg/03209/206344.stm One thing that concerns me about such a system, though, is that the potential level of destruction is pretty danged scary, and there's no fear of fallout or other nuclear contamination to put a brake the decision to use them. Anyway, wondering what people think of the idea.
 
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Nichevo    RE:Rods From God - Hey Blank   6/4/2005 1:49:36 AM
Fine assertions, could you quantify them a bit pleez? I have read suggestions of current long-rod penetrators maxing out at a few hundred feet--pretty sure I could google it up for ya if demanded--what have you been reading may one ask?
 
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andyf    RE:Rods From God -   6/4/2005 9:17:11 PM
surely at high velocity the rod would behave like a meteorite.. ? it hits,, is converted to plasma by its own KE,, explosion,---- circular crater.. like a small clean nuke. how about image recognition software in a smaller stratospheric projectile, that just happens to home in on the overhead silhouette of a T72? no warhead,, just a 2 kg weight, possilbly with a little laser painter on it so you wouldnt get multiple hits on the same target what would that do? practical?
 
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doggtag    RE:Rods From God   6/5/2005 1:28:44 AM
Clay would be rather easy to actually penetrate, MadRat. Mostly, its high water content makes it very pliable. And being soft, the effect would be like shooting a bullet through a stick of butter or cheese (not that I take my anger out on Parkay or chunks of Velveeta to specifically know this), or even ballistic gelatin. The round may actually dissipate its kinetic energy in the soft marl with spectacular results (the surrounding shockwave on the projectile would actually carry through the material a considerable distance.) As opposed to hitting something like a masonry brick (simulates sandstone-type soft/medium density rock), which would absorb most of the energy on impact, I think you would actually get deeper if you penetrated through clay/sand into a target rather than striking solid rock first (and yes, the granite on top of NORAD would be particularly difficult to bore through, even by a hyper-velocity multi-Mach artificial meteorite.)
 
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Heorot    RE:Rods From God -   6/7/2005 5:20:15 PM
The Idea that you are discussing was proposed by Jerry Pournelle His discussion is here: http://www.jerrypournelle.com/slowchange/mega.html Extract: “As an example for discussion, consider the system this author has described under the name "THOR". Thor consists of orbiting steel rods perhaps 20 feet long by one foot in diameter. They contain minimal terminal guidance capability, and a means of locating themselves and their targets through GPS. They can strike fixed targets with CEP approaching 25 feet. Few elements of air and naval power are invulnerable to bombardment by kinetic energy weapons from space. No ship can withstand the impact of 20 feet of steel rod at velocities greater than 12,000 feet per second. Airfields won’t fare much better.”
 
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doggtag    RE:Rods From God -   6/7/2005 5:34:20 PM
Yes but, the kicker is getting them there in the first place (an orbitting weapons platform with couple dozen rods would be VERY heavy, needing astronomical amounts of finances and resources to get it up there. Maybe when we have an established lunar mining operation and lunar foundries, they could be fabricated there and shipped top Earth orbit. But of course, in the long run, that will cost phenomenally more. But the overall benefits may actually be worth the expense. Establishing a reasonable lunar colony would yield incredible scientific ahievements.
 
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Ehran    RE:Rods From God -   6/15/2005 7:10:18 PM
rods that size mass about 400 lbs a foot which is into the dear lord category of overkill for most things i would think. but if you used a steel tube welded to the warhead and used the tube as the casing for a solid fuel booster you could up the terminal velocity a lot while bringing down the mass of the missile a fair bit. could get around the friction problem to some extent i would think with a ceramic coating. then put a layer of that fire gunk the guy on tv showed off and your missile should be ok for the short trip it's got to make. be kind of interesting to see what that sort of thing did to a modern tin warship though. any bets on a relatively small hole all the way through and a whole lot of dead fish around the ship?
 
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   RE:Rods From God -   6/18/2005 7:26:49 AM
It has nothing to do with weapon mass, and not even much to do with terminal velocity. Even if we were to assume a rod with a mass of several tons and a virtually unlimited terminal velocity, you still wouldnt achieve ground penetration of any signifigant depth. This is just the nature of energy release in physics. Like everything else, energy follows the path of least resistance. In this case, a comparably tiny rod striking the very large earth has a tendency to transfer its energy to itself and then AWAY from the earth. This is why explosives create craters: though the earth itself may have been the target, most of the energy is transfered through the weapon (which fails, structurally, VERY quickly after impact) and upward into the atmosphere (as sound, heat, and air displacement). You would need an impossibly survivable impact device to NOT do this (that is, a rod that was more stress tolerant than the entire earth) in order to achieve linear gains in penetration depth as velocity and mass are increased. In the real world, theres no such beast. So an earth penetrator of a given size and density has a PEAK velocity, whereby you achieve maximum theoretical penetration depth (its somewhere around 80 feet with todays materials, I think). INCREASEING velocity or mass (and thereby impact energy) at this point actually DECREASES penetration depth (but nets you a bigger CRATER). Hope that was clear.
 
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K-OS    RE:Rods From God -   1/16/2006 10:56:50 PM
Im an idiot when it comes to physics, but oh well. First of all, they are not aiming to strike at the earth itself, but rather at a bunker underground. Even if the rod doesn't penetrate, the resulting shockwave would be enough to shatter the strongest of concrete walls that would compose a bunker. Also, the bunker would have to be very deep underground to avoid the rod or to be away from the shockwave.
 
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hybrid    RE:Rods From God -   1/18/2006 2:23:28 PM
If shockwaves were what you wanted to do there are easier ways to do that than put something way up into orbit like the "Rods from God" idea. Its cheaper and a lot easier to put a nuke on target to take such a structure (underground or not). Its also far cheaper and easier to seal off the bunker exits and entrances (including airvents) via sometimes conventional bombing or ground strikes and for a kicker if you really want send in an army group of engineers, let them drill to a certain depth then start filling the holes with blasting charges. Do it in a certain way and you can collapse a bunker complex completely.
 
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TrustButVerify    RE:Rods From God - latecomer notes   1/18/2006 10:23:58 PM
Shoot- I'm late to the party on this thread, all the good points have been made. I'll shuffle off to my cave with this- The only Rods from God (RfG) scenario which springs to mind is the system presented in Heinleins seminal classic *The Moon is a Harsh Mistress* in which preexisting lunar catapults (normally used for putting minerals in low Earth orbit) are adapted for firing slugs of rock at point targets. This sidestepped the economic and technological problems of putting several tons of steel rod into a high orbit by assuming a pre-existing system adapted for bombardment purpose. The relatively well-known Steven Den Beste wrote about it briefly as well but I'm glad to say Hybrid has done an excellent job of summing up in his second post. Honestly, I don't know how this thread got this far without someone mentioning Heinlein already. The man is practically the patron saint of this stuff, not that he'd much care for the idea. As for the physics of how such an impact plays out, a fellow named J. E. Enever published an article ("Giant Meteor") in the March 1966 issue of *Analog* and later republished in *Analog 6*. Among other points made therein, he does point out the interesting fact that a sea impact is potentially more damaging than a land impact- this partly due to the huge amount of steam generated. Something to consider, if you really *must*, when discussing naval targets.
 
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