I am assuming all the scifi writers who have theorized the use of long rods or poles of very hard materials like tungsten had a reason for doing so.

If you did assume that the whole projectile immediately disintegrates on impact and all of the kinetic energy it had translates perfectly into the explosion which causes all the damage, to penetrate even 100 meters of solid rock you'd need an object weighing tens of thousands of tonnes at a velocity of 9km/s. Not something you'd routinely drop out of a satellite. A tungsten telephone pole, for example, would only weigh a few tonnes.

I know I backed out, but may I make a suggestion: Shape-charged explosions. Kinetic energy and direction might turn the telephone pole into a giant shape-charged explosive when it hits.

If you just want it to function like a penetrator, a tungsten pole probably won't do the the trick. If you drop it from orbit, it won't hit vertically. Unless you slow it down significantly or somehow give at VERY violent shove downwards, it will hit at shallow angle. Even if we got it to hit at 45 degrees, that means 144 meters of rock to go through. Momentum preservation then gives us something like a 30 meter tungsten pole required, provided that the pole doesn't deform at all against the ground (which is probably an unrealistic assumption). That's a really long pole. Even then you're just delivering some very hot tungsten at 0 speed - that's localized damage to the bunker. And that's provided you even hit where you're supposed too. We're talking an extremely fast projectile travelling 1000s of kms with a lot of inertia and very little maneuverability trying to hit an exact spot on the ground at a shallow angle, then going through over 100 meters of rock and still being on target. Plus if it overpenetrates, then your superheated rod of tungsten just passes right through the bunker with minimum damage, just like shaped charge warheads do against APCs.

The idea just isn't feasible. You can't get that deep, and you don't do any damage anway. Penetrators isn't the way to go (except to carry explosives underground ofc).

I think Lilith meant the impact would turn the Thor shot into something like the bolt of molten metal a shaped charge produces, not a Thor round with a shaped charge warhead.

Assuming it's not molten metal to begin with by that point. By the time it hits the ground, it'll be covered in plasma and leaving a massive firey trail behind it. Part of the reason orbital railguns would be useless against things in atmosphere. Even, possibly, ICBMs.

Smokeskin, except, you might want to know this:

Lilith, if you read back a bit, you'll see that I thought that these things generate very large explosions when they hit. Which corresponds nicely to what you quoted, mentioning nuclear weapon effects.

What I'm arguing against is these things functioning as penetrators (as in the rod actually going down there) against bunkers 100 meters down.

Meh. I'm merely mentioning, at this point, that the total kinetic energy potentially creates shape-charged nukes. When it hits and the tungsten is pretty much destroyed, the potential remaining kinetic energy, combined with the already-existing plasma (which should have shaped the front of the pole to be something closer to a spike anyway) could easily potentially be driven downward, generating the necessary damage through incineration combined with force. If the shaping I mentioned has happened, then quite possibly you have the world's largest spike launcher.

@Lilith: I actually think that more like the opposite happens - the explosion happens at the front, trying to send the rod backwards again. Like with meteor strikes, where you sometimes see pieces of it actually getting hurled back out into space. Basically I don't think the rod has any chance of making it through the "explosion".

@Austere
The length-to-penetration ratio doesn't alter significantly with higher velocity. This is a widely accepted approximation AFAIK.

In the army I was taught that simple HEATs weren't effective at killing lightly armored vehicles. Many were modified with some sort of trailing "plug" that would knock a piece of light armour into killing fragments, or some had 2-stage detonations that effectively meant you got an explosion in the cabin. Basically the jet alone won't kill the crew inside light armor. I don't know how accurate that is, misconceptions about weapon effects are pretty common, even among so-called professionals.

AFAIK the principle of bunker busters are to get explosives into or as close to the bunker as possible. Kinetic kill of bunkers, I just don't see how a penetrator going through a bunker would do anything except some very localized damage.

Getting a 10 kiloton explosion is rather a lot to ask for. If you impact a 1-ton rod at 9 km/s, that kinetic energy is equivalt to 10 tons on TNT. That's still one big bomb. If you effectively get a groundbased detonation, that's very unimpressive. But if you effectively get an underground detonation, that could be very powerful.

If what you're saying is true then, again, the whole weapon is pointless. Inaccurate, inefficient, ineffective. And all those other people theorizing about the weapon, in the US DoD and elsewhere, and all those scifi writers, are wrong.

@Austere: I think you added a kilo too much to some numbers, 0,1 kiloton sounds about right for tactical nukes. A tungsten pole will carry that amount of kinetic energy, so it doesn't have to generate it from nothing.

The HyStrike missile project mention going through 5-10 meters of concrete. That is very different from hitting something through 144 meters of rock. These missiles are probably also not blunt penetrators, like a tungsten pole dropping from orbit will be.

@Shrike: These whole discussion is about whether or not a tungsten rod will just penetrate, so you can't just assume that it will. And the "better minds than us" all seem to list massive explosions from the bigger thor shots, so the reasonable thing to assume is that it won't penetrate, but rather that the pressures at impact will generate massive heat that turns stuff into plasma and yada yada big explosion. Probably not just a ground detonation explosion, if the pressure takes just 3/1,000th of a second to build up you're at the max depths of current conventional penetrators, and you have the energy of a tactical nuke instead of just 300 kg of conventional explosives - and I have no idea how that is going to turn out, how much is heat, how much is shockwave, and if the massive momentum of the pole will direct much of it downwards.

All W48s have been dismantled. The massive majority of all warheads in use by all countries for all purposes are in the 100kt+ range for yield -- this includes all warheads currently active in the US stockpile, no matter how "tactical".

http://en.wikipedia.org/wiki/B61_nuclear_bomb
A 0.3 kiloton nuclear bomb.

http://www.ucsusa.org/global_security/nucl...ng-weapons.html
"For a penetration depth of three meters and a yield of 0.3 kilotons, the B61-11 could destroy a target buried under roughly 15 meters of hard rock or concrete".
This is not far from the effect you expect to get from a tungsten pole dropping from space, referring to the calculations on the kinetic energies carried above.

http://www.globalsecurity.org/military/sys...ns/hystrike.htm
"This phenomenon makes hypersonic weapons well suited to attacking hardened or deeply buried targets such as command bunkers or biological-weapon storage facilities."
"Penetration of 18-36 feet of concrete"
Compare 5-10 meters of this weapon, apparently well suited to attack deep, hardened targets, to the 15 meters of the above-mentioned method.

http://en.wikipedia.org/wiki/Nuclear_bunker_buster
"Rocket sled testing at Eglin Air Force Base has demonstrated penetrations of 100 to 150 feet in concrete when traveling at 4,000 ft/s. [...] Variation in the speed of the penetrator can either cause it to be vaporized on impact (in the case of traveling too fast), or to not penetrate far enough (in the case of traveling too slow). An approximation for the penetration depth is obtained with an impact depth formula derived by Sir Issac Newton."
Seems to indicate that vaporisation in fact does occur when hitting concrete at high speeds. Also seems to indicate that penetration depth approximation was experimentally verified and very long penetrators were used.

I think that you guys are reading "Thors penetrate deep, hardened targets" and then you're guessing that that must mean much deeper than is actually the case, and to make that fit you have to twist the effects into something they're not. Firing a rod of anything a 100 meters underground is probably just impossible without the penetrator vaporizing. If there is any non-nuclear solution to hitting something that deep it could be to ram something so hard that the vaporization from the impact generates a powerful enough "explosion" to destroy the bunker.

How would the impact of this device effect people and material in the bunker without penetrating it at all?

During Vietnam with Operation Linebacker the B52's dropped huge ass bombs all over that country. The shock waves alone were killing people. And Vietnamese soldiers were talking about the shock waved sucking the air out of their deeply buried forts. Enough so, it would sometimes suck the air out of their lungs and knock them out.

So with that kind of energy being delivered to the hardened bunker or just to the stone above it has to do something to the people inside, even the materials/equipment inside.

The different versions of the B61 can be set to have a yield of anything from 0.3 to 350 kilotonnes, as you know if you read those articles. I assume the 0.3kt is achieved with the fission device alone, so that either the fusion fuel is removed or somehow deactivated. This is the equivalent of firing a 155mm HE with a fuze only and the secondary explosive removed -- and saying that the B61 is a 0.3kt nuclear bomb is like saying the M107 HE 155mm projectile has an explosive payload of ~100 grains.

While I think that no one here questions the penetrative ability of a tungsten rod dropped/guided from space, I think that maybe 100 meters is possibly alittle farfetched.

How many bunkers are actually 100 meters underground? In SR or RL, what is the Average depth of a bunker? It seems like 100 meters would require the center of a decent sized hill or in a volcano like an evil genius.

Well, because there are people who will want to building something that is beyond the 10-17m of concrete that a conventional SHOC could penetrate...

Without using a nuclear weapon.

Well, I had a post prepared... But Smokeskin pretty much said it already. Oh well.

Karma, you can safely assume that the entire discussion under which those two were said is over.

...ahhh....linear mass drivers.

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