Anti-Matter weapon

[Plushie]

Since said weapons don't exist in reality, we can't quantify how much yield is practical (from the mixing efficiency of M and AM).

This is about as useful as asking 'what happens if a bomb goes off in XYZ'. Or 'how many people could a big sandwich feed?'

Yield is what matters, not the kind of bomb.

Actually, we can make a few rough guesses. The figure of 9E13J/g has been cited as the energy-density of a M/AM reaction. If we want to be generous and assume 5% efficency in an operational weapon, 15kg of M/AM would deliver a blast-yield equivalent to a 16MT nuclear device.

To put things into perspective, a nuclear fusion device of similar yield, detonation codenamed Castle Bravo, ended up weighing in at something to the tune of 10,600 kilograms all told. That is, in the neighborhood of 700 times as much as the matter/anti-matter device. When you consider that an anti-matter bomb might not need to carry its matter reactant with it, that can halve the total weight of the fuel supply.

Even assuming containment for the anti-matter is stupidly heavy, anti-matter bombs would be feather-weights in comparison to nuclear bombs of similar yields.

[Sea Skimmer]

Even assuming containment for the anti-matter is stupidly heavy, anti-matter bombs would be feather-weights in comparison to nuclear bombs of similar yields.

And safety concerns would make them practically unusable, while a nuclear device would almost certainly cost less and wont go off even if the airplane carrying it explodes and crashes.

[Nephtys]

Antimatter bombs are absurdly impractical. A nuclear bomb is easy to make by comparison, able to be done so by modern technology. If a hyperadvanced civilization can make an antimatter weapon of comparable yield to a nuke, they can certainly bend some tricks and produce a better nuke with their material and design advances.

Antimatter weapons will also be inherently less safe and prone to accidental, catastrophic detonation. Such is just not possible with a nuke.

[Alan Bolte]

There are papers out there discussing the best ways to annihilate anti-matter since any design would have to have decent efficiency to be worth it, which means getting the AM to react instantly at one point, rather than have most of it blown away.

I don't really get it. Why does it matter if it all blows up at the exact same point in the exact same fraction of a second? The antimatter blown from the center of the explosion would simply contact the matter in the atmosphere around the central point of the explosion. How could any of it fail to react?

[Nephtys]

There are papers out there discussing the best ways to annihilate anti-matter since any design would have to have decent efficiency to be worth it, which means getting the AM to react instantly at one point, rather than have most of it blown away.

I don't really get it. Why does it matter if it all blows up at the exact same point in the exact same fraction of a second? The antimatter blown from the center of the explosion would simply contact the matter in the atmosphere around the central point of the explosion. How could any of it fail to react?

I'd imagine for the same reason uncontrolled nuclear fission produces more bang than waiting for a peice of uranium to decay. If you react it all immediately, it's a massive release of energy which would produce an impressive blast.

If it's less efficient, a small amount produces said blast, the rest of the material gets scattered and only reacts minorly, producing some relatively inconsequencial radiation all around, instead of contributing to the main effect. There's still a lot of space between matter in atmosphere after all.

[Thinkmarble]

It is actually an EXTREMELY efficient reaction, with nearly 100% conversion of "stuff" into radiation.

Sorry. pet peeve of mine ^_^

[drachefly]

I'd imagine for the same reason uncontrolled nuclear fission produces more bang than waiting for a peice of uranium to decay.

Problem: M/AM is NOTHING like nuclear fission or fusion. In both nuclear cases, you need to get a fairly rare material into high density. Once it spreads out, it stops exploding. In M/AM, you need to get an extremely rare material to mix with an extremely common material. If you end up spreading it out, it'll still find reactant somewhere and produce 100% energy yield.

If it's less efficient, a small amount produces said blast, the rest of the material gets scattered and only reacts minorly,

in particular, there is no such thing as a minor M/AM annihilation. They meet, and they scatter or annihilate.

producing some relatively inconsequencial radiation all around, instead of contributing to the main effect. There's still a lot of space between matter in atmosphere after all.

The mean free path of an air molecule is approximately 100 nanometers. This is roughly speaking the distance one can travel before meeting an air molecule by going in a straight line

Divide this by the fractional cross section of the nucleus... 1km.

So you've spread half of the energy release (the part that went up instead of down) out over a sphere a kilometer across. If you have a nanogram of AM, yeah, that's going to roughly halve the effectiveness. If you have a couple kilos, that dispersion is much smaller than the blast radius, so it basically doesn't matter. It might actually help spread the damage.

[Broomstick]

It is actually an EXTREMELY efficient reaction, with nearly 100% conversion of "stuff" into radiation.

Sorry. pet peeve of mine ^_^

Peeve all you want. Last I checked, radiation was still considered a form of energy.

[GrandMasterTerwynn]

Okay sorry to give a limit how about 15 pounds?

Converting 13.6 kilograms of matter and antimatter to energy will release the energy equivalent to a 292 megaton nuclear bomb. While the nuclear bomb releases its energy in a very short amount of time, and in a very small area. The antimatter bomb will, due to its own extreme volatility, immediately blow itself apart, leaving most of the antimatter unused, and chasing after the explosive shockwave. Each fragment of antimatter which finds something to react with will, in turn, blow itself apart. The end result is an energy release which will take place over a much greater volume and over a slightly greater period of time. The M/AM annihilation will produce lots of high energy gamma rays, which will collide with stuff, be absorbed, and re-radiated on down the EM spectrum until the density of the fireball drops enough that it becomes transparent, resulting in an intensely bright fireball many kilometers wide which expands rapidly. Depending on the type of anti-atom used, you will certainly generate highly radioactive fallout as protons are randomly removed from surrounding atoms, transmuting them into radioactive isotopes of lighter atoms.

[Enigma]

If I have my math right it should be about 292 megatons

Like I said - a FUCK of a big explosion, but not enough to generate a mushroom cloud over all of North America.

Oh, and for those of you who didn't pay attention in high school physics... the formula for determining the amount of energy in a lump of matter is:

E=mc^2

E=energy
m=mass
c=speed of light

The problem is, my calculator can't handle squaring the speed of light. Also, be careful you don't bollix up your units of measure. You'll get a fuck of a large number no matter what you do.

Energy measured in joules(or kilojoules)? Mass measured in kilograms and the speed of light in kilometers?

[Patrick Degan]

I don't really get it. Why does it matter if it all blows up at the exact same point in the exact same fraction of a second? The antimatter blown from the center of the explosion would simply contact the matter in the atmosphere around the central point of the explosion. How could any of it fail to react?

It wouldn't fail to react; but that's not quite the point, however. The likely result is that the dispersed particulate anti-material would react with surrounding particulate matter and disappear in a flash of gamma radiation. You'd have very heavy gamma in the area of the blast, but by no means the sort of event which would result if 100% conversion of the bomb's fuel upon firing was feasible (it's not).

[Patrick Degan]

Antimatter bombs are absurdly impractical. A nuclear bomb is easy to make by comparison, able to be done so by modern technology. If a hyperadvanced civilization can make an antimatter weapon of comparable yield to a nuke, they can certainly bend some tricks and produce a better nuke with their material and design advances.

Antimatter weapons will also be inherently less safe and prone to accidental, catastrophic detonation. Such is just not possible with a nuke.

There is very little (if anything) that can be done to significantly improve the design and performance of present-day nuclear weapons beyond where they're at.

As for the alleged "inherent un-safety" of an M/AM bomb, one possible engineering solution might entail storing the AM in a sealed, polarised bottle —which does not require horribly complex, fragile support machinery.

The one objection which remains is cost: antimatter weaponry can only exist if an extensive infrastructure to manufacture AM fuel for spacecraft propulsion exists. An ordinary fusion-powered society will not have M/AM bombs; a fission-powered one certainly will not have such things. Of course, the other question which arises is: what sort of threat would require the production of antimatter weapons in the first place.

[Broomstick]

Oh, and for those of you who didn't pay attention in high school physics... the formula for determining the amount of energy in a lump of matter is:

E=mc^2

E=energy
m=mass
c=speed of light

The problem is, my calculator can't handle squaring the speed of light. Also, be careful you don't bollix up your units of measure. You'll get a fuck of a large number no matter what you do.

Energy measured in joules(or kilojoules)? Mass measured in kilograms and the speed of light in kilometers?

It works equally well with both Imperial and Metric - just don't mix the two systems, and mind your units of measure, particularly with the Imperial system. Speed of light is a constant, of course, and never varies - so measure it however you want: miles per second, kilometers per hour, furlongs per fortnight. Use a compatible unit of mass for your "m" value. The units E comes out in is dependent upon what you used for m and what you used to measure c.

I always thought "kiloton" and "megaton" were Imperial units despite the metric prefixes - if they have metric equivalents by the same name, well, they probably ain't the same quantities. At least in the US, "one kiloton" refers to the explosive power produced by one (Imperial) ton of TNT, which is not a metric unit of explosives. The metric tonne (note spelling difference) is actually 10% larger than the Imperial variety, and should probably have been called a "megagram" or something like that.

[Nephtys]

Antimatter bombs are absurdly impractical. A nuclear bomb is easy to make by comparison, able to be done so by modern technology. If a hyperadvanced civilization can make an antimatter weapon of comparable yield to a nuke, they can certainly bend some tricks and produce a better nuke with their material and design advances.

Antimatter weapons will also be inherently less safe and prone to accidental, catastrophic detonation. Such is just not possible with a nuke.

There is very little (if anything) that can be done to significantly improve the design and performance of present-day nuclear weapons beyond where they're at.

As for the alleged "inherent un-safety" of an M/AM bomb, one possible engineering solution might entail storing the AM in a sealed, polarised bottle —which does not require horribly complex, fragile support machinery.

The one objection which remains is cost: antimatter weaponry can only exist if an extensive infrastructure to manufacture AM fuel for spacecraft propulsion exists. An ordinary fusion-powered society will not have M/AM bombs; a fission-powered one certainly will not have such things. Of course, the other question which arises is: what sort of threat would require the production of antimatter weapons in the first place.

Like I said. By the time a civilization can practically make such weapons in usable quanities, barring some kind of new and sudden revolution that makes Antimatter production trivial... by then, they'd surely have learned something to make alternate weapons more useful.

If not improving nuclear bomb yield and reducing mass, they'd figure something else, like using bomb-pumped lasers or something else. Antimatter is just plain tricky to get.

[Sea Skimmer]

As for the alleged "inherent un-safety" of an M/AM bomb, one possible engineering solution might entail storing the AM in a sealed, polarised bottle —which does not require horribly complex, fragile support machinery.

Umm, but what happens if the bottle simply breaks or loses polarization? Nuclear bombs have been physically smashed to pieces (not to mention been consumed inside of explosions) in a number of accidents, so that is a very valid safety standard. Now that the new ‘insensitive high explosive’ is being used there isn’t even much of a risk of the conventional HE charge of US nuclear weapons exploding, something which has happened in earlier accidents.

If not improving nuclear bomb yield and reducing mass, they'd figure something else, like using bomb-pumped lasers or something else. Antimatter is just plain tricky to get.

A bomb pumped laser doesn't increase firepower or reduce mass though; it increases weapon mass but makes a fraction of the existing firepower directional. Current nuclear weapon designs are already 99% efficient or better (the first nukes ranked around 10%), there just isn’t any more energy to squeeze out of them.

[dragon]

Out of curorisity would an M/AM bomb have an emp.

[Batman]

Out of curorisity would an M/AM bomb have an emp.

If it's an in-atmosphere detonation I don't see why not.

[Patrick Degan]

As for the alleged "inherent un-safety" of an M/AM bomb, one possible engineering solution might entail storing the AM in a sealed, polarised bottle —which does not require horribly complex, fragile support machinery.

Umm, but what happens if the bottle simply breaks or loses polarization? Nuclear bombs have been physically smashed to pieces (not to mention been consumed inside of explosions) in a number of accidents, so that is a very valid safety standard. Now that the new ‘insensitive high explosive’ is being used there isn’t even much of a risk of the conventional HE charge of US nuclear weapons exploding, something which has happened in earlier accidents.

The AM bottles in the bombs could be swapped-out before a "expiration point" is reached on its polarised lining (or the lining could be periodically "recharged"). And as for breakage (due to accidental dropping, I'd presume), it should be possible to seal the reactant in an impact-casing durable enough to not shatter excepting when a high-velocity plug is fired into it —which is how I'd envision an M/AM bomb being engineered.

[Surlethe]

Out of curorisity would an M/AM bomb have an emp.

A high-altitude nuclear detonation produces an immediate flux of gamma rays from the nuclear reactions within the device. These photons in turn produce high energy free electrons by Compton scattering at altitudes between (roughly) 20 and 40 km. These electrons are then trapped in the Earth’s magnetic field, giving rise to an oscillating electric current. This current is asymmetric in general and gives rise to a rapidly rising radiated electromagnetic field called an electromagnetic pulse (EMP). Because the electrons are trapped essentially simultaneously, a very large electromagnetic source radiates coherently.

Since a M/Am weapon releases energy initially as gamma rays (proton+antiproton = two gamma rays), there should be an EMP, by the same mechanism as a nuclear weapon.

[XaLEv]

Energy measured in joules(or kilojoules)? Mass measured in kilograms and the speed of light in kilometers?

Joules, kilograms and meters/second.

At least in the US, "one kiloton" refers to the explosive power produced by one (Imperial) ton of TNT, which is not a metric unit of explosives.

http://fermat.nap.edu/books/0309085063/html/36.html

First footnote:

A kiloton is the energy unit usually used for specifying the energy released in a large explosion. Originally it was taken to be the energy released by a thousand tons of TNT, but a kiloton is now defined as a trillion calories (4.2×10^12 joules).

[Sea Skimmer]

If it's an in-atmosphere detonation I don't see why not.

You get a strong EMP with an out of atmosphere initiation; inside an atmosphere most of the energy which would become an EMP is converted into other forms of radiation

[darthdavid]

http://www.schlockmercenary.com/d/20050604.html

[Winston Blake]

If it's an in-atmosphere detonation I don't see why not.

You get a strong EMP with an out of atmosphere initiation; inside an atmosphere most of the energy which would become an EMP is converted into other forms of radiation

AFAIK generally the higher the altitude the better, but you still need to ionise atmospheric atoms to get the EMP currents, so a nuke in outer space wouldn't make a pulse.

[Batman]

AFAIK generally the higher the altitude the better, but you still need to ionise atmospheric atoms to get the EMP currents, so a nuke in outer space wouldn't make a pulse.

That's what I was getting at, thanks.

[drachefly]

Re: sticking AM in a polarized container: There is no electrostatic bottle. In order to confine something you need magnets.