I'd like to make a number of points, forgive me if this might take a while.

1) What is the intended use of this weapon? As I see it the rod's only utility is as an effective bunker buster. And it's rather limited at that. If the yield of the weapon is in the 100 tons of TNT range, we dare not use it to attack say a government/military HQ or bunker located in a populated area. Sure we'd vaporize the bunker, but how about the children's hospital across the street? Or the housing development one block over? We wouldn't need it to take out a single tank, or SAM facility. It's overkill. Besides, the US military has already proven it's ability to wipe out entire Iraqi tank divisions using conventional weapons and tactics. Twice. Use it as an anti-ship weapon? An Exocet, Harpoon, or Sea Eagle can already do the job quite effectively. So basically we're left with Tora Bora as a target. And how many of those have we found lying around?

2) Whatever the vast cost of the US nuclear arsenal might be, and I'm not even going to bother arguing with the $3 trillion figure, it was not all spent for 1 single limited purpose. We developed several generations of ICBMs, intended both to deter an attack and ensure a punishing blow against any aggressor. SLBM's, ALCM's and gravity bombs were built to guarantee the survivabilty of a nuclear response, or counterstrike. We built nuclear tipped air-to-air and surface-to-air missiles to defend against enemy bombers and incoming ballistic missiles. Nuclear armed torpedoes and depth charges to destroy enemy surface and submarine forces. Nuclear tipped artillery shells and land mines (yes, land mines) to stop a ground assault.

3) Refitting an ICBM with a conventional or kinetic impact warhead was never attempted because we never had a reason to do so. As you can imagine, firing off a couple of ICBMs to take out Gadaffi or Ho Chi Minh might have unintended consequences if the Russians weren't sure they were armed with high explosives instead of nukes. However, this is not to say it was never considered. Please see the following link. It's a bit dated and is nothing more than an abstract, but you might find it interesting.

http://www.airpower.maxwell.af.mil/a...pj/london.html

4) Folks are suggesting that our inanimate tungsten rod will have an accuracy of 25 feet. Are you serious? That's shooting at a bullseye only 5 feet larger than the length of the projectile, from an altitude of 200-400 kilometers, after being deployed from a platform presumably in a polar orbit, traveling at a velocity of 40,000 km/hr with respect to the target. William Tell would be proud. You're suggesting using a GPS guidance system and aerodynamic manoeuvering fins. Consider that NASA cannot communicate nor receive telemetry with the space shuttle or Apollo capsules during certain periods of re-entry. Would our rod have the same problem? I can't even begin to estimate the ablative effect of re-entry and it's consequent changes in the rod's trajectory. Once the rod has reacquired the GPS signal, how much time would it have to compensate for these errors while traveling at 11 km/sec? Quite the engineering problem you'd have on your hands.

5) I also have to question the wisdom of deploying such an expensive, and in my mind limited capability, weapons system without considering how vulnerable it would be to countermeasures. The original poster alluded to this scenario. While preventing such an attack after it has been launched may be incredibly difficult, the weapons platform would be a sitting duck beforehand. A rather mundane hunter-killer satellite could be launched into a parallel orbit, close in on your weapons platform, and detonate its warhead. You wouldn't even need anything like a nuke, simply HE and a whole bunch of ball bearings. Ball bearings made of tungsten. Damage the rod-releasing-mechanism, solar panels, gyros, attitude thrusters, communications antennae or onboard computers and your left with 850 metric tons of orbital debris. The Russians launched and tested such a killer-sat back in1963.

6) I hate to bring up cost again, but my earlier estimate was strictly limited to the launching of the suggested mass of tungsten. I did not include the mass of the orbital platform and fuel. Even the best commercial satellites have a useful life of about 10-15 years. So count on periodically replacing or servicing your weapons platform. By the time you factor in research and development, deployment, ongoing operations, and replacement costs, your "cost effective" tungsten rod will have a unit price likely exceeding $300+ million. For the cost of 1 tungsten rod, the USAF could buy over 12,000 slightly less effective BLU-109 satellite guided 2000 lb bunker buster bombs.