I have read extensively the Nuclear Weapons FAQ pages at http://nuketesting.enviroweb.org/hew/Nwfaq/Nfaq0.html

They have LOTS of information on nuclear weapons and their effects. What you would most likely be interested in is section 5, which talks about what happens during a nuclear explosion, in a step-by-step approach.

As for your ideas, first I must point out that the largest nuclear weapons that exist don't get most of their energy from plutonium, enriched uranium or even fusion! It's natural uranium that provides most of the punch! The idea that you had about having a shell of plutonium is actually being done, but it's uranium, not plutonium. The reasons why are simple: it's cheap and abundant, and unlike fusion, it's easier to construct a supercritical mass.

That's not to say that plutonium and nuclear fusion aren't being used. Quite the contrary! Plutonium is used because it is the easiest to construct into a critical mass, and the easiest explosion to control. Unless its a small bomb, the plutonium exists only to trigger the fusion explosion. The fusion explosion in turn send out the high-energy neutrons that are needed to fission U-238, and the shell of natural uranium does the rest.

However, given all of that, one would still need to detonate a sizeable nuke fairly close to a spacecraft to punch a hole into it. Ablative shielding would help if the bomb is 30 or so kilometers away, but if it is within 10 kilometers away, the shields would accomplish very little. Quite the contrary, they would absorb the energy of the bomb and vaporize with explosive force, adding to the already considerable EMP and radiation damage from the bomb. Regardless of what it is made of, anything with a couple of hundred meters of the bomb would immediately be turned into hot plasma. That is no less true in space than it is here on Earth. Also, because there is no air to absorb and re-emit the radiation into the visible wavelengths, the gamma and X rays from the bomb would penetrate the shielding farther away than they would on Earth, and immediately vaporize them. That would be like having plastic explosives for shielding, then detonating them all at the same time! As a result, the bomb would immediately destroy any spacecraft that is nearby, regardless of construction.

"Shaped" nukes might be possible, but it would require multiple nukes timed to perfection. Also the effect would be mainly local, so I don't think that it would provide much of a benefit in destroying a hardened target. If the target spacecraft is a colony deep in an asteroid or something, the only way to destroy the target would be to use multiple nukes to "tunnel" your way in, and they would have to distant enough from each other that one nuke wouldn't disable the next one in line. The soviets had plans like that to dig their way into NORAD during a full-scale nuclear exchange. However, since each nuke would have to detonate in the hollow crater left by the last nuke, one failed detonation could leave the remaining warheads impacting harmlessly on the ground before detonation.

The best defense against such a barrage in space would be defensive lasers and/or missiles. That would be far more effective than any armor.

Enjoy!

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If E = MC², why do I have less energy the more mass my body acquires?
That is all.

--Azpod... Formerly known as James Justin

I'm pretty sure fusion weapons' oomph comes not from the plutonium or uranium trigger, but from the resultant fusion of tritium and dueterium.

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PC load letter? What the @%$# does that mean?

<font size=-1>[ This Message was edited by: overrated on 2002-09-05 22:17 ]</font>

Yes, it does. About 30% of it. The remaining 70% comes from the fission of U-238 that is allowed because of the fast neutrons spit out in the fusion process. Check out the NWFAQ if you don't believe me.

H-Bombs use a 3 stage process: fission (plutonium or U-235 trigger) -> fusion (H2 & H3) -> fission (U-238, lots of it)

The REALLY big bombs chain that process even more, since each stage can drive the energy for even more fusion which can supply the fast neutrons for even more fission. Thankfully, these bombs don't work well for loading onto bombers or missiles, since they are so large.

Clarification: yes, you can create bombs that are multi-stage that are "clean" such that past the first fission-triggered stage, each fusion stage is compressed by a lead sheet, not natural uranium. But while you can create large bombs this way, it is not much more expensive to double or even triple the yield by using natural uranium instead of lead to compress the fusion fuel in each stage.

This, of course, is a "dirty" bomb, which would cause a great deal of lingering radiation on Earth, but (aside from having your target in low Earth orbit) would simply blow away with the Solar wind if used in space.

_________________
If E = MC², why do I have less energy the more mass my body acquires?
That is all.

--Azpod... Formerly known as James Justin

<font size=-1>[ This Message was edited by: Azpod on 2002-09-05 23:59 ]</font>

Aren't these the exact kinds of bombs that the B-52s were designed to carry? Think back to Dr. Strangelove and how it only had two bombs in the whole bomb-bay.

Personally I have better feelings about "dirty" bombs than "clean" ones since it takes the people in charge being that much more insane to actually try using them.

I'm VERY uncertain, but I thought that the EMP effect came from the unleashing of HUGE numbers of electrons ("Beta Rays") in a fission explosion. If you flood the vicinity with electrons, it makes sense that unshielded electronics will suffer damage.

I'm also minded that the photographs of atom bomb explosions were carefully edited (censored) to hide the lightning strikes that paralleled the bomb tests. As I understand it, the EMP effect was a "military secret" until the Soviet Union got their own bomb tests going.

Silas

Here's a quote from the FAQ above on EMP. Sounds like what your describing is largely correct.

Since the EMP descriptions above involve gamma rays hitting air molecules, I don't think much EMP would be generated in space, execpt maybe in nearby spacecraft where the gamma rays can reach the internal atmosphere.

I'm not an expert, but Tom Clancy's book, "The Sum of All Fears" seems to have a layman's description of a nuclear explosion that fits well with what I've read on the FAQ

As a side note the FAQ had this to say about fallout.

It goes on to say that "These radioactive products are most hazardous when they settle to the ground as 'fallout'."

Kizarvexis

The real economic damage from EMP stems from the fact that "currency" (bank notes and coins) represent less than 10% of the total money supply. The rest (90+%) exists solely as data stored on computers. A few muti-megaton explosions over say LA, KC and NY and "poof" there goes your bank account, your retirement fund and the entire economic system.

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Any day you wake up on "the right side of the dirt" is a good day.

T. Anderson

That at least is something that movies have gotten correct. In Goldeneye a major plot in the movie was to transfer money from banks in england to off shore accounts and then use the orbiting bomb to destroy all the records of the transactions.

Though it did make me wonder why truely vital systems wouldn't be shielded against such attacks. Am I correct in thinking that a simple faraday cage would be sufficient to protect against emp?

Am I correct in thinking that there is a practical upper limit for atomic weapons, but no theoretical upper limit for h-bombs?

As for the neutron-bomb, it was designed as an anti-tank weapon, to take out whole divisions of rampaging Soviet tanks without destroying Germany. One proposed defence against it was coating tanks with (I think) zirconium, so ditto for spacecraft.

Possibly your kinetic weapons of choice against enemy space craft might be electronically-activated rifle-calibre rounds. A current Australian design (dreamt up by an Aussie in his garage, I kid you not!) has a rate of fire of a million rounds per minute. If each round was Depleted Uranium Core, Californium Tipped then they'd make a mighty big mess of whatever they hit, and you could pump out thousands of the little swine.

As for nukes, perhaps what you want is a MIRVMIRV Splinter Pack, where one bus releases a dozen separate homing missiles, each of which releases a dozen homing warheads (some dummies, some decoys). 144 warheads from a single missile, each warhead with randomised trajectory alterations to make laser-counter targetting harder.

Or, rather than having nuclear missiles, you could use nuclear mines. Have the enemy come to you, as it were. Bait enemy spacecraft into your minefields and Kerblammo! Of course, you'd need to have *really* accurate maps.

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Garlic Bread?!?!

A million rounds a minute? What the... that's insane. The GAU-4, which, as far as I know, has the highest rate of fire of any automatic cannon used in the U.S. military, only does 6,000 or so a minute.

How would you cool such a weapon? How many barrels would it have? Is it rifled? You'd have to carry a ton (maybe literally) of ammo, that's for sure....

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PC load letter? What the @%$# does that mean?

If I remember correctly, the original gadget involved lining up ordinary rifle bullets in a tube, and discharging them (electrically?) in such a way that they all essentially went off at the same time. The result was described as a "cylinder of lead" flying through the air.

Much like the "rail gun" concept, it only works once, quite destroying the tube in the process... But, yeah, the concept could support "insane" rates of fire.

re upper limits of fission bombs...nope. Just keep building up shells of Uranium...

re "directional" warheads, I'm reminded of the notion of using fission bombs as propulsion for a space-ship. (I saw this on tv, demonstrated in a scale model, using ordinary explosives. The first "bang" pushed the ship up a few inches; the next pushed it up a few feet; the third pushed it up a few hundred feet...) In the same way, then, a "staged" sequence of bombs could propel the final warhead (whether inertial, energy-based, or whatever) at one heck of a final speed...

Silas

That could have been Orion or Medusa. If my memory serves me correctly, with orion bombs are simply dropped out of the back and a heavy lead plate is used to take the force of the blast. In medusa the blast is captured by a parachute like sail that makes the effect of a pulsed nuke engine less jarring.
Both aren't fit for manned missions for reasons that should be obvious.

Does anyone know anything about safer ways to get going fast? Ion engines, plasma rockets, ntr, etc?

Also just because something has a firing rate of a million rounds per minute, doesn't mean you have to carry a million rounds.

If the bullets were in a tube and they were expelled electrically causing them to all be fired at once, it was most likely a gauss rifle. Though I haven't heard of a practical one yet.

(now why are all my posts showing up with small text?)

<font size=-1>[ This Message was edited by: Paul Best on 2002-09-08 00:01 ]</font>

"A million rounds per minute ..."

I should explain a bit further, or at least what I know. The "gun" consists of a series of tubes held in a square frame, each tube holding one bullet. There are several frames arranged one behind the other. When the bullets in one frame are fired, they all go at once, followed by those in the next frame within a fraction of a second. The effect has been described as a "death ray of lead".
So, if you had a frame 1000 tubes wide by 1000 tubes tall and discharged them all simultaneously then you'd have an rpm of something like 1,000,000 rounds per second ... at least.

Another weapon might be hungry little microbots. If it were possible to make them -tropic to materials used in spaceship design (ferro-tropic? Aluminotropic? Micatropic?) then a cloud of them could be deployed along an approach trajectory. Spaceship travels through cloud, picks up miniature hitch-hikers, gets corroded to bits.

Then there's micro-filaments. Say spun sapphire, kept in a web a thousand kilometres wide by - ooh, I dunno, electrostatic forces? (complete guess there, folks)- hard to spot, liable to slice and dice anything travelling into it.

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Garlic Bread?!?!

Actually, yes there are upper limits to the yield of pure fission devices. Shells of uranium outside the core of the bomb need to either be at supercritical mass or bathed in neutrons to detonate. The former is very difficult to do because the compression wave from the core of the bomb going nuclear would tend to blow the shells apart, rather than compressing them into a critical mass. If you are trying to compress the shells from the outside prior to detonating the core, and forcing them to reach critical mass that way, all you are doing is building a bigger core. There is an upper limit to how big the core can get before it will meltdown on its own, and a larger core means a greater chance that a stray neutron will prematurely set off a chain reaction as you're in the process of compressing the core towards critical mass, thereby causing predetonation and drastically cutting your yield down.

Also, while any shells of uranium will be bathed in neutrons from any nuclear explosion, a fission explosion releases far fewer neutrons per kilogram than any form of nuclear fusion. So while you can boost the yield some by having an extremely dirty bumb made up of a core and numerous U-235 shells outside of the core, the theoretical upper limit is one fission for every stray neutron from the core. (And in reality, it is actually much lower.) Since the size of the core is limited, the total yield for a pure fission device is limited, no matter how dirty it is.

The only way to create a pure fission device of unlimited yield is to have multiple cores that all go nuclear at exactly the same time. The technology for doing that is currently well beyond us, as one would need to compress multiple cores, get them to supercritical mass without any stray neutrons causing predetonation, and fire neutrons at all the cores such that the neutrons reach each one at exactly the right time for optimal yield. If ANYTHING goes wrong, one core will detonate first before the others reach peak criticality, and the remaining cores will all predetonate. While you can theoretically build enough cores to reach any level of yield, even given predetonation, it is FAR more efficient to use even a small amount of fusion to ensure that any uranium shells you may have receive well over the amount of neutrons needed to ensure optimal yield.

Also, fusion devices can be multi-staged, which is something that is impossible to do with fission devices. The reason multistage fission devices are impossible is because prior to compression, the cores for any additional fission stages are all but certain to receive numerous stray neutrons, preventing them from reaching optimal critical mass before they simply melt down.

<a href = "http://nuketesting.enviroweb.org/hew/Nwfaq/Nfaq4-5.html#Nfaq4.5">
Section 4.5 for the Nuclear Weapons FAQ has lots of into on multistage weapons</a>

_________________
If E = MC², why do I have less energy the more mass my body acquires?
That is all.

--Azpod... Formerly known as James Justin

<font size=-1>[ This Message was edited by: Azpod on 2002-09-08 18:34 ]</font>

I believe that rounds per minute is judged simply on how many bullets would be fired in one minute at the guns rate of fire. A million rounds a minute would allow for 1666 rounds in one second. The ammount of bullets actually fired doesn't matter, and neither does the reload time. Machineguns typically don't carry enough ammo for a minute of constant firing, but are still rated in rounds per minute.

Then again I might be wrong.

From your description now it sounds less like a gattling gun, or a machine gun, but a lot more like one of the weapons you'll often find at civil war reenactments, or at the start of an exhibit on automatic weapons. four small cannons all on the same carraige, all with the same wick. The strategy of simply filling the air with lead is also a rather 19th century concept.

Typical problems with micromachines would apply, mainly targeting, they don't descriminate, and if they're self replicating how do you stop them from spreading?

In any sensible sci-fi universe, such weapons would be as illigal as biological weapons are today.

People are constantly trying to ban landmines, but haven't yet succeeded. So I suppose this one is actually somewhat believable. How would it be kept in place though? Wouldn't something like that act like a solar sail and constantly drift away from where you wanted it?

Though it might make a good missile based weapon, fire a missile, it splits in two, and between the two is a better than razor sharp blade traveling at hypersonic speeds? Cheaper than a beam weapon, if a little slower.

Would one of these fibers be strong enough to cut through a spaceship?

Keeping a net in place wouldn't be very hard. Simply attach some weights to the edges and give it a slight spin. The spin not only keeps it open, it also keeps it in a single orientation, like a gyroscope. Light pressure from the Sun might be a problem, but if it's made of molecularly-thin wires, and dark, there wouldn't be much effective surface for it to work on.

I agree that it probably wouldn't be a very effective mine-type weapon though. A ship would have to encounter it at a very high velocity for it to do much damage. Since it has a large surface area, any impact would be spread out over the entire area of contact. It might not be able to cut through unless it was going very fast. I guess it would depend on how dense you made the weave. A tight weave might be too dense to penetrate the ship, whereas a loose weave would cut better, but there'd be less filaments to cut with.

The missle idea sounds good though. Give them a large thrust and send the wire towards the enemy. Slice and dice. But it would probably do better as a loose web strung between several missles than a single thin wire. More area to hit with. But what's to make this more desirable than a simple missle with a shrapnel-filled warhead and a proximity fuse?

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...And that, my liege, is how we know the Earth to be banana-shaped. --Sir Bedevere

I believe that is 4,500 rpm. The sea whiz (MK 15 Phalanx CIWS) for anti-missile protection.

http://www.fas.org/man/dod-101/sys/ship/weaps/mk-15.htm

Available on the USS Coral Sea (CVB 43) and USS Wisconsin (BB 64). In the handy "What the heck was that" pack.

Next is the GAU-8 which fires at 4,200 rpm. Available on the A-10 Thunderbolt in the handy "Where'd my tank go" pack.

But, in a handy dandy Google search, I have found others with higher rpm.

M61A2 - 7,200 rpm.
GSh-6-23 (Soviet) - 12,000 rpm (installed on Su 24Ms)

But, why use high tech when low tech will do and make a neater noise. Firing solid metal missiles at a target makes nice holes in an enemy and are economical, too. No problems with radiation or being too close to the blast area.

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Valiant Dancer