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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, 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: 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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hybrid    RE:Rods From God   4/3/2004 11:07:58 PM
Oh geeze not this one again ::straps on his helmet and dives into a trench:: ;) If no one else explains the problems I will but I'll let the others have a crack at it since they do an extremely good job.
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Vossiewulf    RE:Rods From God   4/3/2004 11:10:18 PM
LOL, I guess I better take a better look where I step;-) I'd be interested in why it's problematic, but if it's one of those discussed-to-death things, don't worry.
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hybrid    RE:Rods From God   4/4/2004 12:02:04 AM
Eh I'm bored at this I'll give ya a couple of reasons right off the bat. 1) KE. Depends on velocity and PE, PE being turned into KE from the height of its orbit to target, the angle the rod comes back into the atmosphere and what lateral velocity has it been given? Problems start occuring here, say you have a 1 ton mass (we'll get to actual materials problems in a sec) by the time it hits say a terminal velocity of say mach 30, your mass will give an impact equivalent of 5 tons of nominal TNT. For this, how much money have you spent lofting the payload into orbit, quite possibly several million bucks. 2) KE and materials engineering again. After a certain amount of depth into the ground you get major ground shear forces acting to rip apart any rod so that it doesnt stay intact. This basically kills any KE capability of the rod to penetrate very deep because it tends to break in two or more pieces after penetrating a certain depth. I believe the current testing has put it around 20-30 meters? Don't quote me on that though as I could be majorly overstating the actual depth achieved. 3)Thermodynamics. You got a major problem here too. Reentry velocity induced atmospheric friction will turn to fluid even tungsten, and DU is naturally pyrophoric which means you'll start losing structural soundness because it keeps burning off layers or having it turn to a plasma like state. which brings us to point number 4) Namely anything re-entering atmosphere from orbitals has a plasma sheathe form around it (its around the space shuttle and ballistic missiles as well). Nothing really gets through this sheathe, so the only way to transmit data is by finding the lowest temp area of the projectile and using a trasmitter there, and hopefully that will help with guidance, because if not then you got serious re-entry problems regarding atmospheric densities and wind currents which can major your projectile miss by hundreds of meters or even kilometers. I think that covers some of the problems :) Jerry Pournelle actually was one of the ones that first came up with the idea. In theory it sounds great. In practice not so great unless you're already on a spot like the Moon and dont really give a hoot about super precision.
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Vossiewulf    RE:Rods From God   4/4/2004 12:18:54 AM
Thanks Hybrid, I appreciate the explanation. I'd thought of 4), thinking you might have to use intertial nav rather than GPS due to the reentry blackout, but I didn't think that was a big deal. On the other hand, looks like the estimates I'd previously read of the kinetic energy and penetration capability were wildly off;-) If that's the scoop, then yeah, certainly no point in putting something like that into orbit. Of course that begs the question as to why it'd have official sanction, as in an active research project, unless they just like spending money, or do they think there are solutions? Ah well, back to other things.
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hybrid    RE:Rods From God   4/4/2004 12:03:17 PM
"Of course that begs the question as to why it'd have official sanction, as in an active research project, unless they just like spending money, or do they think there are solutions?" Mainly because research into these ideas also spawns research like into new boosters which can be used for delivering other things. Or even new materials could be potentially developed. Like I said..In theory the system has some points in favor of it. In practice..its very hard to do.
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Taliban Killer    RE:Rods From God   5/21/2005 10:51:34 PM
The math of the nergy involved (1ktonn is ~10^12 J for comparision) Assuming a terminal velocity of 30 Mach and a 1 tonne projectile 30*333 m/s= ~10,000 m/s KE=1/2 mass * velocity^2 =1/2*1000*10,000^2 =50 gigajoules 1000 gigajoules is approximately 1kT Not so bad, really, especially if the energy is concentrated on a very small spot. The problem is, to get that kind of terminal velocity (assuming zero friction) by gravity alone would require starrting around 4000 kilometers above the earth (the space station is at around 200km).
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jhaley    RE:Rods From God   5/23/2005 6:56:02 PM
Most of the major problems mentioned with the Rods from God concept have been overcome, with the exception of the cost and practicality. So whats realy going on, is the DOD just throwing dollars down the drain for a system that will never be funded or is the rods from god just a cover project for whats realy going on....A hypervelocity projectile operating in suborbital space for a manned or unmanned weapon system.....?
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   RE:Rods From God   6/2/2005 3:49:50 PM
Even a KE projectile dropped from low earth orbit would still have insufficient terminal velocity (and net KE) to penetrate more than a few meters, assuming you were able to solve the obvious logistical problems of getting it into orbit, and getting it to survive re-entry. Not worth the cost.
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MadRat    RE:Rods From God   6/3/2005 2:52:36 AM
I'm sure it could pick up enough speed to break the sound barrier several times over, which is plenty of energy to penetrate soft earth hundreds of feet. Sand and gravel are much harder to get good effects on, and solid rock I'm sure its fairly useless. It would take too large of projectile to confidentally punch through a fortress like NORAD. But punching through ten to twenty feet of concrete hidden under soft earth is definitely possible...
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MadRat    RE:Rods From God   6/3/2005 2:57:25 AM
I read your 20-30M mark in the earlier post. I know a Mach 3 tungsten tipped warhead was able to penetrate a sand-clay mix to 150 feet. I'd think clay would be tougher to penetrate then softpack earth because clay is such fine particulate and doesn't compress well.
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