Talk:Antimatter weapon

Hmmm...the interesting thing about antimatter weapons is that they can be very small. A thimble full of antimatter is enough energy to blow up an entire city. If you could somehow hold the antimatter in a small "bottle", you could have a pocket sized nuke. Samboy 10:23, 30 Jan 2005 (UTC)

Perhaps, but producing the stuff seems to be prohibitively difficult, much less containing it in a small "bottle." I also don't think it would change the strategic/political situation of the world any more than nuclear weapons do (you can make fission weapon small enough to fit into a backpack). --Fastfission 22:41, 2 Feb 2005 (UTC)

A thimble full of antimatter? Hah! It costs billions of dollars just to produce a few atoms of it. --NoPetrol 02:00, 24 Feb 2005 (UTC)

Yes, it is expensive. For now. But so were computers, there is always a higher inital cost of development, and as the technology matures costs drop. How much? Who knows... --Zotel 11:32 EST July 24, 2005

Yes, but we are many, many orders of magnitude away from a practical "pure" antimatter device right now. There seems to be fundamental physical limits to how efficiently antimatter can be produced (giving an efficiency of maybe 0.1% in production), and there's not much available naturally (you might collect it with satellites from stuff captured in the Earth's magnetic field, but there's only miniscule quantities and it would be a massive undertaking). And energy costs, while tending to generally drop in real terms over time, drop at a fairly slow rate. So the energy required to make an antimatter arsenal seem unlikely to become practical, particularly when you can cook a nuclear weapon up in your back shed (well, not quite, but South Africa did it in secret for a few tens of millions of dollars), and as Fastfission pointed out the Americans made backpack-size nuclear weapons back in the 1950's. --Robert Merkel

Odd line

The article suggests that the production of "antimatter bombs" would be a foolish economic endeavor because the energy that would be required to produce enough antimatter for the bomb would be equal to the energy that the bomb would release.

This doesn't make any sense to me. This seems to imply that trying to use antimatter as fuel (as some sort of reactor) would be economically foolish (as you wouldn't net anything). But for a bomb, I don't think net energy gain is the point—it's about making something blow up. So even if it took a fission bomb's worth of energy to construct a fission bomb, it would still be worth it if it could instantly be delivered on another city, for example. I'm not saying I think that an antimatter bomb is practical but I'm not sure that this sentence really proves that point... perhaps others have thoughts? --Fastfission 22:55, 2 Feb 2005 (UTC)

Yeah - That's true - explosives are powerful not so much because they have a lot of stored energy, but because it's released quite rapidly, so there not being a net energy gain wouldn't be a problem. The problem (for would be antimatter weapons developers) is that they either have to produce the antimatter in advance and find a way to transport it without it reacting with any matter along the way, or they have to find a way to rapidly produce it right where they want it to detonate. And in the latter case, the lack of a net-energy-gain would be a problem. --Blackcats 06:13, 15 Apr 2005 (UTC)

Mass needed?

The Atomic bomb page states that just a gram of anti-matter would produce many times the energy of a standard nuclear weapon when destroyed. This page says it would take several kilograms -- who's right? One or the other needs to be corrected (I don't know which)

Actually, it just states that one gram of anti-matter would produce more energy than a 20KT nuclear device. You need half a gram to match Hiroshima bomb, 10-30 grams to match a typical modern nuclear warhead, slightly over 1 kg to match Tsar-Bomba.

Disputed

In the event of an antimatter detonation in the open atmosphere, most of the energy will ultimately be carried away by the neutrinos, and the remainder by 10-100 MeV gamma rays. The neutrinos would pass through the earth without being attenuated, while gamma rays are relatively weakly absorbed by matter: they lose roughly half of their energy per 500-1000 m of air, compared to only 20 cm of concrete. The explosion would not cause much physical damage because its energy would be evenly dispersed over large area, although the gamma rays may harm people standing nearby.

This seems to be quite incorrect - compare with Nuclear explosion, which states (correctly, as far as I am aware), that a large part of the energy of a regular nuclear explosion is released as gamma radiation, and it is quickly absorbed by the nearby air, superheating it and creating the fireball of the explosion. The same would most likely happen in an antimatter explosion, making it much the same as any nuclear explosion (minus the 60% lost to neutrinos).

--130.232.31.109 01:11, 10 July 2005 (UTC)

According to [1], kinetic energy of fission fragments accounts for 90% (170 out of each 190 MeV) of energy generated in a nuclear explosion, not counting neutrinos. Those gamma rays that do get produced have much lower energies and thus lower attenuation lengths. --Itinerant1 19:03, 10 July 2005 (UTC)

Well, that is no doubt a good point. However, you still can't dismiss the gamma energy like the article does - just the secondary visible-wavelength light from a normal nuclear explosion does a lot of burn damage even before the shockwave hits. Gamma rays might not get attentuated much by air, but they will get absorbed when they hit the ground, or buildings. And the energy radiated and absorbed will be huge, even at longer distances.

--130.232.31.109 17:52, 11 July 2005 (UTC)

Absolutely, a megaton is a megaton, even in gamma spectrum. The point is that, if there is not enough shielding material in the vicinity of the explosion, you won't have a usual shockwave. You'll have a huge ball of hot air ( and it won't be particularly hot: 1 kiloton of TNT can heat up 1 km³ of air by only 5 Kelvin ). Imagine all of the energy that goes into visible light from a conventional nuclear explosion, instantaneously absorbed within 1 km of epicenter. Then you'll have some interesting dynamics of this fireball - it will probably start expanding and then rising off the ground (due to Archimedean force), some fraction of energy will be reemitted as visible light; a mushroom cloud is not unlikely. Those gamma rays that do reach the ground will still be potent enough to kill exposed people within a few km. --Itinerant1 18:51, 11 July 2005 (UTC)

Prices?

The pricing of $25 billion per gramme conflicts with the $25 million per gramme on the Antimatter page, and the $2.5 million per gramme lower limit in this article. Clarification please! Was the billion figure meant to be for a Kg?--81.178.104.55 00:07, 20 October 2005 (UTC)

Originally Antimatter page quoted $25 billion per gram. The number in this article was copied from there verbatim. On July 13, 2005, someone replaced $25 billion with $25 million. I don't know which of the two figures is correct. --Itinerant1 03:01, 20 October 2005 (UTC)

All of the above estimations are incorrect. The actual cost TODAY of antiprotons which are needed to produce neutral antimatter is several million trillion US dollars per gram, as estimated below, 1 gram of antimatter contains 6x10^26 antiprotons + positrons. The Antiproton Decelerator facility of CERN can produce 4x10^12 antiprotons per year, at an operation cost of around $20 million including the 25-GeV proton synchrotron. Cost per gram is then around 1x10^19 dollars and it would take until the end of the earth to produce a gram. --User:137.138.16.5 17:48, 20 October 2005 (UTC)

CERN facility is research-oriented, not production-oriented, and may not be the cheapest possible antimatter factory. This article estimates production cost of antiprotons at CERN of $1.6*10^14 per gram, and it goes on to describe improvements that can lower it to $6.4*10^12 per gram. Robert L. Forward, apparently, predicted sometime during the '80's that antimatter could be produced at $10 billion per gram, but I can't find any good links. --Itinerant1 17:39, 21 October 2005 (UTC)

I think that all physicists would regard the contents of the paper you mention (i.e.producing antiprotons by simply putting two parallel plates together and using the Casimir effect) to be bad pseudo-science. Also the antiproton production rates discussed in the introduction of the paper is far too optimistic and analyzed by non-experts who ignore the limits of accelerator technology. 10^7-10^8 antiprotons per proton bunch has been the limit at CERN and FNAL for many years, and even at the future facility at GSI. This is NOT because these facilities are "non-dedicated" etc. as these papers seem to claim. It is because of space-charge limitations in the accelerator which collect the antiprotons, efficiency of the stoachastic and electron cooling needed to cool down and decelerate the antiprotons, heat loading on the target used to produce the antiprotons. Now using various techniques (build an entirely new superconducting linear accelerator, liquid metal production targets, cascade of antiproton storage rings) it may be possible to increase that limit by maybe factor of 100, but there is NO way it would ever get nearly efficient enough to build weapons and rocketships and do these fantastic things. --User:137.138.16.5 17:37, 22 October 2005 (UTC)