Prophet710 wrote:

so you could theoretically have an antimatter grenade/rocket then? I mean obviously you can in larger yield weapons such as ICBM/StS torpedoes, but, something smaller yield is "possible". How would you go about containing it so it wouldn't annihilate when you go to throw it?

One problem with this is that the containment unit for housing antimatter has to be much larger than the antimatter it is holding. For instance, the emergency farcaster has an antimatter bottle the size of an orange, yet only holds 10 nanograms... enough to torch the body its contained in, and nothing more. So you're not looking at much antimatter being contained in a portable housing. You need them [i]big[/i].

I had these in the Firewall guide to unconventional weapons. They are usually seeker rounds, making use of a gentler acceleration than a kinetic firing mechanism (which is on the order of 100,000 G). Remember, if the weapon knows what accelerations will occur and can compensate for them, then the suspension will hold. My thinking is this: the containment unit is at least an order of magnitude bigger than the antimatter. Let's make that two. A bullet weighs a few grams, and presumably can have a payload of say a gram. That would be mostly containment, with about 0.01 gram of antimatter. That has an energy of about 219 tons of TNT - that beats the Russian FOAB quite handily, but is still far from a tactical nuclear weapon. But it shouldn't be too hard to scale things up a bit... if you are willing to get an even more unstable weapon.

It all depends on parameters GM feels are correct for AM containment. How robust is the system (what kind of shocks, accelerations, etc. the mechanism can stand?), size (volume and density for given capacity) and similar (power requirements?). It could be anything from Alastair Reynolds' "Hot Dust" in [i]Revelation Space[/i] (Ie. pinhead for kiloton or two and an absolute security nightmare) to steamer trunk of expensive and ticklish hardware (in which case most crazy terrorists go with proven solution of Old School suitcase nuke). What do you think fits best in the campaign is the way to go, I think. Personally, I'd go with the 'bulky and ticklish' approach; the crazy terrorist standby is not AM, but 'old and proven' laser-triggered suitcase-sized 'pure fusion' D-T warhead. It can be fabricated in any 'jailbroken' matter compiler with very few monitored materials and the blueprints have been spread across the system by Anarchists for a long time. Extremely rugged, detonating flawlessly even after receiving obscene amounts of abuse. Comes with non-stepped variable yield, from one-ton TNT equivalent to 400 kilotons... Sorry, channeling Yuri Orlov there for a bit... :P

Arenamontanus wrote:

I had these in the Firewall guide to unconventional weapons. They are usually seeker rounds, making use of a gentler acceleration than a kinetic firing mechanism (which is on the order of 100,000 G). Remember, if the weapon knows what accelerations will occur and can compensate for them, then the suspension will hold. My thinking is this: the containment unit is at least an order of magnitude bigger than the antimatter. Let's make that two. A bullet weighs a few grams, and presumably can have a payload of say a gram. That would be mostly containment, with about 0.01 gram of antimatter. That has an energy of about 219 tons of TNT - that beats the Russian FOAB quite handily, but is still far from a tactical nuclear weapon. But it shouldn't be too hard to scale things up a bit... if you are willing to get an even more unstable weapon.

Given that the emergency farcaster is "~ size of an orange" and contains ~10 nanograms (MUCH less than 1 centigram) of antimatter, I doubt a much smaller bullet contains .01 g antimatter. I'd be surprised if a bullet could contain even .000000001 g of antimatter. That is still an very high amount of energy, but hardly 219 tons of tnt... In my opinion, larger, industrial sized/spacecraft-type antimatter containment facilities do not scale down efficiently to emergency farcaster sizes... However, I could be wrong, and the writers decide the farcaster contain less antimatter than it COULD for safety reasons only, and your city block razing bullets may indeed be plausible.

From a theoretical standpoint, how would the containment device scale with antimatter payload? The magnetic field needed to hold 10 nanograms, would it really need to be that much stronger to hold 10 micrograms or 10 milligrams?

Smokeskin wrote:

From a theoretical standpoint, how would the containment device scale with antimatter payload? The magnetic field needed to hold 10 nanograms, would it really need to be that much stronger to hold 10 micrograms or 10 milligrams?

I think this would be tricky to calculate. Suppose you have a device rated for accelerations up to a, where the mass m of antimatter is kept suspended surrounded by a vacuum gap of width d. If the suspension is thought of as a spring, the spring constant has to be ma/d or higher to keep it from the walls. For example, 10 nanograms with a 1 N/m constant and a 0.1 mm gap can handle accelerations up to 10 million G. But it would have a resonant frequency of about 300,000 Hz - if something starts to shake it around that frequency it might build up enough oscillation to slam into the wall; how well it can be dampened depends a lot on how it actually is suspended. Now, if the antimatter is magnetic with a magnetization of M (likely about a million A/m, like an iron magnet), volume V and density rho (likely on the order of 1000 kg/m^3), then the total mass m is Vrho and the total magnetic moment MV. In a magnetic gradient DB the force will be DB*MV. Putting it together rho/d M must be less than DB: with these numbers we need a field gradient of about one Tesla/m. (Note that the antimatter volume disappears from the equation: what matters is just the ratio of density to magnetization). One Tesla/m sounds quite doable with current or EP tech. Now, I don't know how magnetic field strength scales with generator size. Looking at the formulas for electromagnets bigger is not necessarily better: higher current certainly helps, but has limits based on the limits of superconductivity. I suspect there is still a volume effect (since field strength is dependent on area and number of coil windings), but having smaller flux paths also increases things.