The Straight Dope

Go Back   Straight Dope Message Board > Main > General Questions

Reply
 
Thread Tools Display Modes
  #1  
Old 12-08-2012, 11:38 AM
s0meguy s0meguy is offline
Guest
 
Join Date: Jun 2012
Antimatter warhead

I've a couple questions about antimatter weaponry.

Yes, I know that at the moment it is infeasible to create a large enough amount of it for use in weapons.

1) Would an antimatter warhead cause a mushroom cloud like a nuclear weapon? If yes, what would its shape be like compared to a conventional nuke and if no, what would it look like, looking at it from a safe distance (in space if need be).

2) Are antimatter warheads the most powerful kind of warheads possible? Since it converts all mass to energy?

3) What would its area effects consist of? A huge amount of gamma radiation and? Would it have a huge shock wave?
3.1) Would it irradiate a large area around, making it uninhabitable for a long time, like in Chernobyl?

4) How much would it take to make uninhabitable an area the size of the US or the whole of the EU? (detonated in the most optimal area for the largest possible area of effect) In kilograms.
4.1) How much would it take to completely annihilate everything in such an area?
4.2) Would the explosion from 4.1 reduce said continent to a giant crater, taking a large chunk out of the planet or would every human (and natural) structure simply be blown away?

5) Are there any promising theorized antimatter production methods (that aren't feasible at this time because of the limitations of other technology possibly)
5.1) Same question for their containment.

Thanks.

Last edited by s0meguy; 12-08-2012 at 11:43 AM..
Reply With Quote
Advertisements  
  #2  
Old 12-08-2012, 11:47 AM
s0meguy s0meguy is offline
Guest
 
Join Date: Jun 2012
6) What would a 9mm antimatter bullet do to a person? Destroy a large chunk of them or just completely erase that person from existence? For convenience assume that 90% of the bullet's mass is antimatter.
Reply With Quote
  #3  
Old 12-08-2012, 11:53 AM
AndrewL AndrewL is online now
Guest
 
Join Date: Sep 2001
Quote:
Originally Posted by s0meguy View Post
6) What would a 9mm antimatter bullet do to a person? Destroy a large chunk of them or just completely erase that person from existence? For convenience assume that 90% of the bullet's mass is antimatter.
A 9mm bullet weighs about 8 grams, so that's 7.2 grams of antimatter. According to this page, 7.2 grams of antimatter reacting with matter releases about as much energy as a 300 kiloton nuclear weapon. I think it's fair to say that the person will indeed be erased from existence, along with a large amount of the surroundings.
Reply With Quote
  #4  
Old 12-08-2012, 11:54 AM
Ludovic Ludovic is offline
Charter Member
 
Join Date: Jul 2000
Location: America's Wing
Posts: 23,275
Quote:
Originally Posted by s0meguy View Post
I've a couple questions about antimatter weaponry.

Yes, I know that at the moment it is infeasible to create a large enough amount of it for use in weapons.

1) Would an antimatter warhead cause a mushroom cloud like a nuclear weapon?
Yes, if it were detonated in air cleanly. Mushroom clouds are caused by thermal gasses rising. Don't know what shape it would be
Quote:
2) Are antimatter warheads the most powerful kind of warheads possible? Since it converts all mass to energy?
I think that kinetic weapons sped up to .99999999c impart more energy than a non-relativistic chunk of antimatter of the same rest mass. I may be off by a few nines, but if so, just throw in some more nines as needed.
Quote:
3) What would its area effects consist of? A huge amount of gamma radiation and? Would it have a huge shock wave?
3.1) Would it irradiate a large area around, making it uninhabitable for a long time, like in Chernobyl?
A huge shock wave and radiation. However, it would be much cleaner than a nuclear bomb as far as fallout goes because it would not contain any primary radioactive isotopes, only those isotopes that were caused by the radiation. I can't say those would be zero but they would be minimal.

Last edited by Ludovic; 12-08-2012 at 11:55 AM..
Reply With Quote
  #5  
Old 12-08-2012, 12:10 PM
Hail Ants Hail Ants is offline
Charter Member
 
Join Date: Jan 2000
Location: NY USA
Posts: 5,470
Semi-educated guesses here:

1. There is nothing uniquely 'nuclear' about a mushroom cloud, any large explosion containing a massive fireball detonated in a planet's gravity & atmosphere will make a mushroom cloud, it's just that really powerful explosions like nukes make very large & distinct ones.

2. They would be several orders of magnitude greater than fission or fusion, but otherwise who knows.

3. If detonated around matter as in on a planet's surface (as opposed to outer space) then:

► Shock wave- Yes (again, that's part of any explosion)
► Ionizing radiation- Probably not

4. I'm sure scaled-up figures exists based on the tiny amounts of antimatter that has been made in labs but what they are specifically I don't know. As for its effect, it would cause an enormous explosion releasing huge amounts of energy (i.e. heat) and if detonated on a planet a huge destructive pressure wave (again, all explosions do). It wouldn't have any special 'disintegration' effects that would vary on living vs non-living or artificial matter, atoms are atoms.

5. No idea.
Reply With Quote
  #6  
Old 12-08-2012, 12:10 PM
s0meguy s0meguy is offline
Guest
 
Join Date: Jun 2012
Quote:
Originally Posted by Ludovic View Post
However, it would be much cleaner than a nuclear bomb as far as fallout goes because it would not contain any primary radioactive isotopes, only those isotopes that were caused by the radiation. I can't say those would be zero but they would be minimal.
So it would sterilize an area, and a new group of people could just move in a short time after the explosion?
Reply With Quote
  #7  
Old 12-08-2012, 12:54 PM
Chronos Chronos is online now
Charter Member
 
Join Date: Jan 2000
Location: The Land of Cleves
Posts: 55,160
It's convenient shorthand to say that an antimatter weapon would 100% convert mass to energy, but in practice, that's not really true. Assuming that your mass is mostly antiprotons and antineutrons, most of your energy is going to end up in neutrinos, which will just pass harmlessly through absolutely everything and carry the energy calmly out into space. There's still plenty left over for a bang bigger than any bomb ever built, though.

That leads into the second problem with antimatter weapons, though: There's no real use for them. The bombs we already have will destroy a city clear out to the horizon. A hypothetical bomb many times more powerful would just destroy the same city out to the same distance. It'd destroy it more energetically, maybe, but the important thing is that it's destroyed either way.
Reply With Quote
  #8  
Old 12-08-2012, 12:55 PM
RickJay RickJay is offline
Charter Jays Fan
Moderator
 
Join Date: Jun 2000
Location: Oakville, Canada
Posts: 32,020
Quote:
Originally Posted by Ludovic View Post
Yes, if it were detonated in air cleanly. Mushroom clouds are caused by thermal gasses rising. Don't know what shape it would be
A mushroom cloud wiull probably be shaped like a mushroom.

It doesn't matter if your big bomb is fuelled by plutonium or antimatter; it's going to look the same. A flash of blinding light and a fireball that rises into the air, leaving a mushroom cloud.
Reply With Quote
  #9  
Old 12-08-2012, 02:13 PM
Sailboat Sailboat is offline
Guest
 
Join Date: Aug 2005
Quote:
Originally Posted by Chronos View Post
That leads into the second problem with antimatter weapons, though: There's no real use for them. The bombs we already have will destroy a city clear out to the horizon. A hypothetical bomb many times more powerful would just destroy the same city out to the same distance. It'd destroy it more energetically, maybe, but the important thing is that it's destroyed either way.
This is like a thought experiment conducted by Edward Teller when he was thinking about "the Super," a theoretically scalable hydrogen bomb design capable of very high megaton explosions. At some point, Teller realized, most of the energy would be spent lifting the atmosphere over your target city into space -- and adding more energy at that point would mostly lift more atmosphere into space without increasing the destructive radius much (and of course, without increasing the deterrent effect of the weapon, which was its primary purpose.)
Reply With Quote
  #10  
Old 12-08-2012, 02:17 PM
Chronos Chronos is online now
Charter Member
 
Join Date: Jan 2000
Location: The Land of Cleves
Posts: 55,160
Oh, and it should also be mentioned that really big conventional bombs, containing nothing more exotic than TNT or gasoline, can also produce mushroom clouds.
Reply With Quote
  #11  
Old 12-08-2012, 02:19 PM
Lumpy Lumpy is online now
Charter Member
 
Join Date: Aug 1999
Location: Minneapolis, Minnesota US
Posts: 12,642
I'm not sure how clean an antimatter explosion would be; the (presumed) antiprotons could collide with heavy nuclei and blast them apart into (presumably) radioactive fragments. To say nothing of secondary effects (pure gamma can induce isotope changes). Cleaner per joule certainly but not fallout-free.
Reply With Quote
  #12  
Old 12-08-2012, 03:28 PM
beowulff beowulff is online now
Member
 
Join Date: May 2001
Location: Scottsdale, more-or-less
Posts: 10,967
Antimatter would make a really lousy bomb.

The beauty of nuclear weapons is all of the matter that gets converted to energy does so in a small fraction of a microsecond. There's no way to "assemble" an Antimatter bomb fast enough to achieve the same fast energy release. Not to say it wouldn't cause a lot of distraction, but a Fusion bomb of the same mass would probably make a bigger bang.
Reply With Quote
  #13  
Old 12-08-2012, 05:43 PM
Chronos Chronos is online now
Charter Member
 
Join Date: Jan 2000
Location: The Land of Cleves
Posts: 55,160
Quote:
There's no way to "assemble" an Antimatter bomb fast enough to achieve the same fast energy release.
I'm not so sure about that. For a fission bomb, you need to assemble it, because the process depends on the expensive stuff being packed very tightly. For an antimatter bomb, though, even if the original configuration of antimatter gets blown apart, all of the fragments are still going to react with ambient matter.

Of bigger concern would be safety. Yes, you want a bomb to explode, but only when it's supposed to. Until it's actually in place, you want it to be very, very hard for it to accidentally go off. Nuclear bombs achieve this, but with antimatter, if your containment system (whatever it is) fails, it's going to blow.
Reply With Quote
  #14  
Old 12-08-2012, 05:53 PM
Johnny Q Johnny Q is offline
Guest
 
Join Date: May 2003
Remember that in most cases, the first matter your antimatter projectile will hit is whatever you're using to shoot it. Best case scenario, it will only take the gun and its shooter out.
Reply With Quote
  #15  
Old 12-08-2012, 05:59 PM
beowulff beowulff is online now
Member
 
Join Date: May 2001
Location: Scottsdale, more-or-less
Posts: 10,967
Quote:
Originally Posted by Chronos View Post
I'm not so sure about that. For a fission bomb, you need to assemble it, because the process depends on the expensive stuff being packed very tightly. For an antimatter bomb, though, even if the original configuration of antimatter gets blown apart, all of the fragments are still going to react with ambient matter.

Of bigger concern would be safety. Yes, you want a bomb to explode, but only when it's supposed to. Until it's actually in place, you want it to be very, very hard for it to accidentally go off. Nuclear bombs achieve this, but with antimatter, if your containment system (whatever it is) fails, it's going to blow.
Think about this:
What makes a bigger bang -8 lbs of TNT or 1 gallon of gasoline burning in air?

Gasoline has 10x the energy content of TNT - the reason it isn't used as an explosive is the reaction rate is limited to how fast the gasoline can be combined with air. Same with antimatter - it would be like throwing a pound of Potassium into a pool. It might make a fun display, but it wouldn't produce an enormous explosion, because on the surface can react with the water around it,
Reply With Quote
  #16  
Old 12-08-2012, 06:04 PM
Chronos Chronos is online now
Charter Member
 
Join Date: Jan 2000
Location: The Land of Cleves
Posts: 55,160
Ah, wait, I see... You're positing the mother-of-all-Leidenfrost effects, with a "vapor barrier" of hard gammas and relativistic particles holding the matter and antimatter apart. I suppose that might work, though I would expect that the initial surface reaction would serve to mix things pretty well.

For the record, though, gasoline burning in air is used in bombs.
Reply With Quote
  #17  
Old 12-08-2012, 06:06 PM
Ethilrist Ethilrist is online now
Guest
 
Join Date: Nov 2000
Quote:
Originally Posted by Johnny Q View Post
Remember that in most cases, the first matter your antimatter projectile will hit is whatever you're using to shoot it. Best case scenario, it will only take the gun and its shooter out.
If we're assuming some sort of long-term safe-storage technology, it's reasonable to assume a non-suicidal delivery method.
Reply With Quote
  #18  
Old 12-08-2012, 06:18 PM
beowulff beowulff is online now
Member
 
Join Date: May 2001
Location: Scottsdale, more-or-less
Posts: 10,967
Quote:
Originally Posted by Chronos View Post
Ah, wait, I see... You're positing the mother-of-all-Leidenfrost effects, with a "vapor barrier" of hard gammas and relativistic particles holding the matter and antimatter apart. I suppose that might work, though I would expect that the initial surface reaction would serve to mix things pretty well.

For the record, though, gasoline burning in air is used in bombs.
Oh, yeah - I'm aware of them.
But, you understand how they work, right? - A large quantity of flammable liquid is spread over a huge volume of air, and then ignited. I don't think that would be possible for an Antimatter bomb (because the individual particles would be reacting as they were dispersed).

I guess we'll just have to make one, and find out!

(It might be fun to simulate this on a supercomputer - anyone have any grant money available?)
Reply With Quote
  #19  
Old 12-08-2012, 06:18 PM
Lumpy Lumpy is online now
Charter Member
 
Join Date: Aug 1999
Location: Minneapolis, Minnesota US
Posts: 12,642
I wonder if antiprotons could be trapped as anions in a crystalline lattice?
Reply With Quote
  #20  
Old 12-08-2012, 07:13 PM
Ludovic Ludovic is offline
Charter Member
 
Join Date: Jul 2000
Location: America's Wing
Posts: 23,275
I wonder -- if this "fizzle" effect would occur with massive antimatter, if we might be able to use it to make less deadly containment vessels. Have massive antimatter all in one place on purpose-- If the container leaks -- streak goes through the sky and irradiates people but no big explosion. It would be engineered so there would only be a big explosion if there were precisely sychronized bits of compressed matter sent toward the antimatter chunk, like they do with a plutonium bomb.
Reply With Quote
  #21  
Old 12-09-2012, 09:16 AM
AaronX AaronX is offline
Guest
 
Join Date: Feb 2011
Quote:
Originally Posted by Ethilrist View Post
If we're assuming some sort of long-term safe-storage technology, it's reasonable to assume a non-suicidal delivery method.
But once the bullet starts traveling in air, it'll react. The reactions might even slow the bullet enough so it won't reach the target.
Reply With Quote
  #22  
Old 12-09-2012, 09:29 AM
Hail Ants Hail Ants is offline
Charter Member
 
Join Date: Jan 2000
Location: NY USA
Posts: 5,470
Quote:
Originally Posted by Chronos View Post
For the record, though, gasoline burning in air is used in bombs.
Well, that's the thing, an FAE (fuel-air explosive) isn't exactly a 'bomb' but more a specialized form of anti-personnel weapon (we also used them in the first Gulf War to clear minefields). The key difference though is that gasoline (like black powder) is a low explosive, while TNT (like gun cotton) is a high explosive. They're both chemical reactions, one is just much, much faster than the other. FAEs are also somewhat unique in that they do not contain their own oxidizer, they have to combine with air to ignite. But this is kind of the point, the gasoline is dispersed into a large vapor cloud which mixes it with huge quantities of ambient atmospheric oxygen, then it's ignited. They don't have the blast pressure of a high explosive, but they create an enormous fireball (which also sucks up all the oxygen adding to its anti-personnel capability). Plus it makes them simple & cheap to produce.
Reply With Quote
  #23  
Old 12-09-2012, 02:24 PM
Ethilrist Ethilrist is online now
Guest
 
Join Date: Nov 2000
Quote:
Originally Posted by AaronX View Post
But once the bullet starts traveling in air, it'll react. The reactions might even slow the bullet enough so it won't reach the target.
Pellet of antimatter in a vaccuum, suspended magnetically in the center so that it doesn't touch the walls, until the container hits something and breaks open.

Teleport the antimatter from orbit to destination.

If I can come up with two high-tech solutions off the top of my head, there are a dozen more. So, assuming we have a way to store the stuff, we will probably be able to figure out a way to get it to the target.
Reply With Quote
  #24  
Old 12-09-2012, 02:30 PM
SandyHook SandyHook is offline
Guest
 
Join Date: Nov 2002
Quote:
Originally Posted by s0meguy View Post
6) What would a 9mm antimatter bullet do to a person? Destroy a large chunk of them or just completely erase that person from existence? For convenience assume that 90% of the bullet's mass is antimatter.
Just something I read a few months ago, no cite, sorry.

The amount of matter converted to energy in the bombs dropped on Japan was about the size of dime. And they were in the 20 kiloton range.

Which sounds like it compares very well with AndrewL's post.

Could you have a 90% antimatter bullet? What little I think I know about the subject is that matter and antimatter react and destroy themselves instantly on contact. Is this true?
Reply With Quote
  #25  
Old 12-10-2012, 08:37 AM
si_blakely si_blakely is offline
Guest
 
Join Date: Jul 2002
Quote:
Originally Posted by Lumpy View Post
I wonder if antiprotons could be trapped as anions in a crystalline lattice?
One SciFi webcomic writer (Howard Tayler, Schlock Mercenary) posits antiprotons stored in a matrix of fullerene - the electrostatic forces from the bound electrons repel the antiprotons so they do not contact anything they might react with.

Si
Reply With Quote
  #26  
Old 12-10-2012, 09:27 AM
Chronos Chronos is online now
Charter Member
 
Join Date: Jan 2000
Location: The Land of Cleves
Posts: 55,160
Nitpick: You can't stably contain anything with just electrostatic, or even magnetostatic, forces. When you trap something in a clathrate (such as a fullerene, though smaller clathrates are possible), it's actually a rather complicated set of dynamic forces that are doing the job.
Reply With Quote
  #27  
Old 12-10-2012, 10:58 AM
Leo Bloom Leo Bloom is offline
Keeping my password unchanged
 
Join Date: Jun 2009
We've produced antimatter in accelerators, right? Why didn't they get blown to smithereens?
Reply With Quote
  #28  
Old 12-10-2012, 11:05 AM
beowulff beowulff is online now
Member
 
Join Date: May 2001
Location: Scottsdale, more-or-less
Posts: 10,967
Quote:
Originally Posted by Leo Bloom View Post
We've produced antimatter in accelerators, right? Why didn't they get blown to smithereens?
A few particles don't make much of a bang.
Reply With Quote
  #29  
Old 12-10-2012, 11:25 AM
Sailboat Sailboat is offline
Guest
 
Join Date: Aug 2005
Quote:
Originally Posted by Leo Bloom View Post
We've produced antimatter in accelerators, right? Why didn't they get blown to smithereens?
Thermodynamics, as always. Can't get more energy out of the antimatter we make than the energy we put into making it. Enough energy from antimatter to blow apart the hardware would have blown apart the hardware while trying to make the antimatter in the first place.
Reply With Quote
  #30  
Old 12-10-2012, 12:26 PM
Leo Bloom Leo Bloom is offline
Keeping my password unchanged
 
Join Date: Jun 2009
Interesting. Thanks.

So, so much for any containment of bang-worthy amounts? Or is "just a question of engineering," as I've heard it put in GQ?
Reply With Quote
  #31  
Old 12-10-2012, 12:33 PM
beowulff beowulff is online now
Member
 
Join Date: May 2001
Location: Scottsdale, more-or-less
Posts: 10,967
Quote:
Originally Posted by Sailboat View Post
...Enough energy from antimatter to blow apart the hardware would have blown apart the hardware while trying to make the antimatter in the first place.
I don't think this is strictly true.
Factories get destroyed all the time by explosions of the product they are making. It's mostly a matter of how long it takes to create the antimatter, and they how quickly it explodes. So, if for (a very hypothetical) example, it takes 100GWH to create enough antimatter to make a 10GWH explosion, that still might destroy the machine if the original energy was supplied over one month, and the explosion occurred in one small spot over a few nanoseconds.

Granted, this isn't the case right now, since there is no effective storage mechanism, and the antimatter is being produced "on-the-fly."
Reply With Quote
  #32  
Old 12-10-2012, 01:10 PM
md2000 md2000 is online now
Guest
 
Join Date: Feb 2009
First, as mentioned above, the "anitmatter bomb" would presumably be encased in a matter-proof container (super-shielding and magentic containment?) thus allowing it to come in contact with pro-matter as soon as the container is cancelled somehow - preferrable at the destination, not the launch.

Any large explosion creates a muhroom cloud. The hot air from the explosion rises, until it loses enough heat and mixes with enough ambient air to cool off and level off. If you watch pictures of spectacular explosions (non-nuclear) in movies, etc, you will see the falling air/smoke as it falls then gets sucked back in to the rising column, providing a rolling "top" that appears mushroom-like.

An atomic explosion (fusion or fission) provides several dozen kilograms of vaporized fission or fusion byproducts - plus a huge burst of neutrons which can cause radioactivity in surrounding material. Fission IIRC releases about 0.1% of the weight of the fission products as energy; fusion, IIRC, was about 0.7% of weight.

Antimatter particles anhilate each other, realsing far more energy, but in the form of photons and neutrinos, which are not going to create much in the way of residual radiation, I assume. I never got that heavily into studying particle physics.

The fizzle theory is interesting. Assuming it is not true...
The explosion of antimatter, like the fission and fusion explosions, is a very localized affair. The damage is done by the massive, massive release of energy, creating a huge heat expansion event and shock wave that destroys the surroundings just like a chemical explosion. Look at the observatory mmorial in Hiroshima. The metal girders of the dome still exist, almost directly under ground zero. The initial energy flash vaporised the copper dome immediately (and vaporized people, leaving "shadows" on the sheltered concrete). Without the copper roof acting as a sail, the bare iron giders of the dome were strong enough to withstand the shock wave that arrived shortly after. The building survived because the shockwave arrived from above, rather than from the side where it would have knocked over the wall.

So damage comes from 2 effects - the intial flash of energy (photons, light, infrared, UV, etc.) and the following pressure wave. There are additional dynamics an expert can tell us more about, like a "suction" effect after the pressurwave has passed, etc. Craters would be most likely caused by a pressure wave rather than the vaporization effect of the energy burst.

Explosive engineering is a fun science. to knock off a chunk of the planet, it helps to position the explosion so that it is "behind" the chunk rather than relying on brute force. (I.e. drill a hole and put the bomb several dozen miles down - hey, an application for that Leidenfrost effect) Plus, once you get to that level of power, even rock is more likely plastic and fluid than to be an immovable block.

How big a hole/crater depends on the size of the bomb; but I am inclined to believe Beowulff's Leidenfrost argument - the bigger the antimatter "bomb" the slower it burns. Alternatively, you could create a matter-antimatter-matter bomb, where the inner core of matter blasts the antimatter shell outward to maximize its contact with matter (when the respective miracle containment field units are turned off of course).
Reply With Quote
  #33  
Old 12-10-2012, 01:54 PM
Glazer Glazer is offline
Guest
 
Join Date: Oct 2007
Quote:
Originally Posted by beowulff View Post
Think about this:
What makes a bigger bang -8 lbs of TNT or 1 gallon of gasoline burning in air?

Gasoline has 10x the energy content of TNT - the reason it isn't used as an explosive is the reaction rate is limited to how fast the gasoline can be combined with air. Same with antimatter - it would be like throwing a pound of Potassium into a pool. It might make a fun display, but it wouldn't produce an enormous explosion, because on the surface can react with the water around it,
Make your anti-mater in the shape of a cup. Inject your matter seed stock through the containment into the cup. Reaction starts inside your anti-mater blowing it outward into surrounding matter to continue the reaction.

Last edited by Glazer; 12-10-2012 at 01:55 PM..
Reply With Quote
  #34  
Old 12-10-2012, 01:58 PM
bump bump is offline
Guest
 
Join Date: Jun 2000
Nobody would bother with pure antimatter weapons anyway. The stuff's far more useful as a boosting agent for existing nuclear weapons.

Basically a precisely timed and very small matter/antimatter reaction at the center of an implosion weapon would be much like fusion boosting, but even more powerful.
Reply With Quote
  #35  
Old 12-10-2012, 03:04 PM
eburacum45 eburacum45 is offline
Guest
 
Join Date: Feb 2003
Here's a cite for Bump's idea of boosted nuclear weapons;
Antimatter induced fusion and thermonuclear explosions

Last edited by eburacum45; 12-10-2012 at 03:04 PM..
Reply With Quote
  #36  
Old 12-10-2012, 03:27 PM
eburacum45 eburacum45 is offline
Guest
 
Join Date: Feb 2003
Quote:
Originally Posted by Ludovic View Post
I think that kinetic weapons sped up to .99999999c impart more energy than a non-relativistic chunk of antimatter of the same rest mass. I may be off by a few nines, but if so, just throw in some more nines as needed.
Actually, its much slower than that. At 86.6% c the energy of a projectile equals the energy that would be produced by annihilation. So a relativistic missile could exceed the energy of a pure antimatter bomb by a large margin.
Reply With Quote
  #37  
Old 12-10-2012, 03:45 PM
Pleonast Pleonast is offline
Charter Member
 
Join Date: Aug 1999
Location: Los Obamangeles
Posts: 5,280
Quote:
Originally Posted by bump View Post
Nobody would bother with pure antimatter weapons anyway. The stuff's far more useful as a boosting agent for existing nuclear weapons.

Basically a precisely timed and very small matter/antimatter reaction at the center of an implosion weapon would be much like fusion boosting, but even more powerful.
I was going to post the same thing.

Reaction time of the anti-matter and matter is not a problem. Fusion is attained in bombs by compressing the core to such high densities and temperatures that the nuclei are close enough to interact. The same densities and temperatures would facilitate the anti-matter annihilation.

~ ~ ~ ~ ~

For really advanced technology, a more elegant solution would be to create a chemically active anti-matter bomb. That is, make TNT out of anti-matter. Triggering the chemical explosion would then scatter the anti-matter over a large volume.
Reply With Quote
  #38  
Old 12-10-2012, 04:37 PM
s0meguy s0meguy is offline
Guest
 
Join Date: Jun 2012
Quote:
Originally Posted by Pleonast View Post
I was going to post the same thing.

Reaction time of the anti-matter and matter is not a problem. Fusion is attained in bombs by compressing the core to such high densities and temperatures that the nuclei are close enough to interact. The same densities and temperatures would facilitate the anti-matter annihilation.

~ ~ ~ ~ ~

For really advanced technology, a more elegant solution would be to create a chemically active anti-matter bomb. That is, make TNT out of anti-matter. Triggering the chemical explosion would then scatter the anti-matter over a large volume.
The point of the antimatter TNT would be just to spread the antimatter right? Or would it significantly increase the power of the explosion independent of the fact that more antimatter annihilates faster because it is farther apart?

What could an anti-matter nuke do? Not boosted, just a nuke made from anti-matter detonated on Earth.

Last edited by s0meguy; 12-10-2012 at 04:38 PM..
Reply With Quote
  #39  
Old 12-10-2012, 05:53 PM
Chronos Chronos is online now
Charter Member
 
Join Date: Jan 2000
Location: The Land of Cleves
Posts: 55,160
Quote:
Quoth md2000:

Antimatter particles anhilate each other, realsing far more energy, but in the form of photons and neutrinos, which are not going to create much in the way of residual radiation, I assume. I never got that heavily into studying particle physics.
You'll eventually end up with nothing but photons and neutrinos, but the first step in the annihilation of a nucleon and an antinucleon is going to be three high-energy pions, which will last some time before decaying (especially the charged pions, which will be more common). And I don't know for sure, but I wouldn't be at all surprised if those pions can trigger transmutation of ordinary nuclei.
Reply With Quote
  #40  
Old 12-10-2012, 07:38 PM
dracoi dracoi is offline
Guest
 
Join Date: Dec 2008
Quote:
Originally Posted by s0meguy View Post
The point of the antimatter TNT would be just to spread the antimatter right? Or would it significantly increase the power of the explosion independent of the fact that more antimatter annihilates faster because it is farther apart?

What could an anti-matter nuke do? Not boosted, just a nuke made from anti-matter detonated on Earth.
An anti-matter bomb would act very much like a standard nuke from the layman's perspective. I'm sure the experts would get excited over small differences in radioactive spectrum or the like, but the basic idea of fireball->shockwave->mushroom cloud->flattened city would be virtually the same. If there's any big difference it's that an antimatter weapon wouldn't have the radioactive fallout afterward.

Since we can already build nukes that are more powerful than is tactically useful, an antimatter bomb isn't even a step forward in destructive capability. (See upthread for some good commentary on that.) Maybe you could make it lighter than a nuke, but probably not so much - even in a traditional nuke, the fissile/fusion material is lighter than the rest of the casing and other bomb components.
Reply With Quote
  #41  
Old 12-10-2012, 08:56 PM
bump bump is offline
Guest
 
Join Date: Jun 2000
I don't know enough about the physics involved, but could antimatter boosting make it possible to have very small nukes that have large yields? Like say... a 100 kt bunker buster that might fit in the casing of the conventional bunker-buster bombs?
Reply With Quote
  #42  
Old 12-11-2012, 03:57 AM
s0meguy s0meguy is offline
Guest
 
Join Date: Jun 2012
Yeah, I was thinking of miniguns mounted on a spaceship for orbital bombardment. According to a poster above, the explosion of a 9mm antimatter bullet would be around the same strength as a 300 kiloton nuclear warhead. Increase the caliber and you can get a megaton per bullet. Put them into a few 10,000 rounds per minute miniguns and a small ship could lay waste to an entire planet.

Assuming improved antimatter production and containment technology.

Last edited by s0meguy; 12-11-2012 at 04:01 AM..
Reply With Quote
  #43  
Old 12-11-2012, 09:12 AM
Leo Bloom Leo Bloom is offline
Keeping my password unchanged
 
Join Date: Jun 2009
Quote:
Originally Posted by s0meguy View Post
.....
Assuming improved antimatter production and containment technology.
It's the only way to be sure.
Reply With Quote
  #44  
Old 12-11-2012, 12:36 PM
Pasta Pasta is offline
Charter Member
 
Join Date: Sep 1999
Posts: 1,713
On irradiation (because I was curious and haven't seen this laid out anywhere) --

I'll take the 9mm projectile as a point of reference and call it 8 grams of antimatter.

Each nucleon-antinucleon annihilation has scores of possible outcomes, with any number of exotic mesons produced alongside the "normal" stuff. The heavier species will decay quickly, leaving most of the energy to deposited via photons, muons, and charged pions. While the photons and muons can transmutate nuclei, their irradiation impact will be small compared to the pions. Essentially every negative pion and about half of the positive pions will cause an ambient isotope to change. If each annihilation eventually results in roughly two charged pions, then that's about 1.5 isotopic changes per annihilation, or about 7x1024 transmutated nuclei.

Even if all of these were troublesome isotopes, the total mass of radioactive material would be about 300 times smaller than in the WWII detonations, so we could probably stop here. However, many of these isotopes won't be troublesome, so things aren't even this bad. The primary transmutation mechanism (charge exchange) can only change one neutron to a proton or vice versa. Very few stable isotopes lying around on earth have long-lived neighbors. Oxygen (the most abundant element on earth) has only 18O-->18F, but even that only lives for two hours and 18O is only 0.2% of the oxygen around. Neither silicon nor aluminum have candidates. Iron and calcium both have some candidates, and one that stands out is 40Ca-->40K, as potassium is biologically active. 40Ca makes up 4% of the earth's crust. Assuming half the irradiation occurs in the crust (and the other half in the atmosphere), then 9 grams of 40K would be created and dispersed. If this falls out over 5000 km2 and mixes in with the top 1 cm of soil, it would increase the natural abundance of 40K by one part in 107. So, nada.

There is also the direct perturbation of nuclei in the annihilation process, but you will still end up primarily with unstable or very short-lived isotopes that won't make it to any fallout stage. Given the safety margin calculated for the irradiation of potassium, I'm not going to go through the math on direct production of long-lived isotopes, as it will come out similarly tiny.

So, it certainly seems like an antimatter weapon would be quite clean.
Reply With Quote
Reply



Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 10:10 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.

Send questions for Cecil Adams to: cecil@chicagoreader.com

Send comments about this website to: webmaster@straightdope.com

Terms of Use / Privacy Policy

Advertise on the Straight Dope!
(Your direct line to thousands of the smartest, hippest people on the planet, plus a few total dipsticks.)

Publishers - interested in subscribing to the Straight Dope?
Write to: sdsubscriptions@chicagoreader.com.

Copyright 2013 Sun-Times Media, LLC.