On 13/9/2002, Donald Lang posted:
The site below is an archive that sticks around for another few days. It needs as always to be rescued if it has gone beyond one line.To save yo'all some effort I have copied the text below my signature thingie
http://www.smh.com.au/text/articles/2002/09/06/1031115939075.htm
The main idea ssems to involve fourth generation nuclear weapons. Someone has sold the writer the idea of making a bomb with anti-matter as a part of the trigger. At the moment this does not compute. Have any of the regular 'users' on the list missed some of their stash recently?
Triggering a fusion weapon with some sort of laser array has been an ambition of some recognised 'talent', but nobody has yet boasted of success. As the lady said "They wouldn't say that, would they?
I am dubious about making baby fission weapons. This may just mean I have not employed the right lateral thought process.
I doubt whether anyone will go after small weapons for bunkerbusting. My thinking may be hopelessly out of date. If anyone is going to use a bomb at all I suspect they will be just as happy to be hated for for a big rambo as for a tiny lambo.
It did fill about a fifth of a square metre in a section dedicated to "thinking 9/11".
Busting the bunker
of non-proliferation
Date: September
7 2002
Concrete and treaties are no match for fourth-generation nuclear weapons, warns Hamish McDonald.
Five months ago the Foreign Minister, Alexander Downer, showed off Australia's most tangible contribution to the fight against the spread of nuclear weapons, an installation on Australia's south-western tip at Cape Leeuwin linked to undersea sensors that can pick up the faintest tremors of a covert nuclear test on our side of the world. But even as the $10 million hydrophone station, and 321 others like it around the world, became operational under a regime enforcing the 1996 Comprehensive Test Ban Treaty (CTBT), there were fears the system was just an anti-nuclear Maginot line, analogous to the French defensive wall the invading Germans simply drove around in 1940.
Since the treaty was initiated, partly due to a huge diplomatic push by Australia at the United Nations, there have been huge breaches in the non-proliferation regimes covering nuclear and related defence areas. India and Pakistan went openly nuclear. The US has rejected the CTBT, withdrawn from the Anti-Ballistic Missile Treaty with Russia, and set up a new military space command. To this picture of a collapsing non-proliferation system, September 11 and its aftermath have added a new ingredient: an increased willingness on the part of some nuclear powers to contemplate use of their nuclear armouries.
What used to be called "unthinkable" is becoming very thinkable indeed in the febrile atmosphere of the expanding war on terrorism. The evidence this year is mounting. It has leaked that Washington's secret Nuclear Posture Review is likely to recommend that new nuclear weapons be developed for "bunker-busting" strikes against underground bases - a reflection of deep frustration in the US military at the limits of air power in striking at deeply hidden al-Qaeda bases in the Afghanistan mountains or suspected secret chemical and biological weapons plants in Iraq. India and Pakistan have gone to the brink of war again over Kashmir, with Pakistan pointedly conducting a missile test to warn India against a punitive strike.
It is still unclear whether nuclear deterrence worked in this theatre, or hidden diplomatic manoeuvres, or both. The British Foreign Secretary, Jack Straw, has warned Iraq that using chemical or biological weapons against British forces could meet a nuclear response, reminding us all that "no first use" clauses have never been in the doctrines of Western nuclear powers and have in recent years been abandoned by the Russians. What is bringing nuclear weapons back into consideration is an array of new technologies that could avoid the well-known ill effects of "traditional" big bombs: massive civilian death tolls, radiation sickness and long-lasting radioactive fallout. After Hiroshima and Nagasaki, big bombs with yields up to the megaton (1 million tons of TNT equivalent) have been unusable, except as Doomsday deterrents.
As an article in a recent Wired magazine illustrates, the US nuclear weapons stockpile is looking as retro as a Chevy classic. No-one is sure whether the bombs and warheads will work properly. The scientists who made them are nearly all retired. Key institutes like the Lawrence Livermore National Laboratory have suddenly realised bomb-making is a dying trade, and have started recruited brilliant young PhDs to preserve the know-how. But it's essentially a curatorial effort. Trying to fit a version of one of those bombs to a "bunker-buster" weapon will prove a technical dead end. The US Air Force has tried dropping long, ground-penetrating bombs from a great height, and got only about 12 metres underground through solid rock. Firing cruise missiles up entry tunnels can be foiled by a right-angle turn or concrete baffle. And the nuclear explosion will still send up unacceptable amounts of radioactivity and cause large-scale civilian casualties.
The emerging world of the "fourth-generation" of nuclear weapons (atomic or fission bombs were the first, hydrogen or fusion bombs the second, and the abandoned neutron bombs the third) has been brought to light largely by the efforts of two Swiss physicists, Andre Gsponer and Jean-Pierre Hurni, and a number of like-minded European colleagues. In a dossier now in its seventh edition, Gsponer lists several processes under scientific testing which may produce workable alternatives to the fission of heavy metals such as uranium and plutonium which act as either the explosive itself, or as the "detonator" for a fusion bomb where the energy is released from hydrogen isotopes. These include the super-laser, a bench-top apparatus capable of producing energy fields intense enough to trigger nuclear fusion, and the use of antimatter, produced for fractions of a second in laboratory conditions. Even the fission process could be modified, replacing the uncontrolled chain reaction of an atomic bomb with a "subcritical fission burn" that still releases massive amounts of energy. Gsponer sees weapons built on such technologies filling the "gap" in military arsenals between conventional air-delivered bombs (about 10 tons maximum) and the smallest traditional nukes, in the kiloton range.
Military people are frustrated at having multimillion-dollar, high-precision weapons like cruise missiles that can carry only a few hundred kilograms of conventional explosive, he says. "It is clear that the military would like to have something that would make these delivery systems more cost-effective," he says. The fourth-generation weapons would be characterised by extreme compactness, depending on how the trigger mechanism could be miniaturised. A subcritical fission bomb with a yield of several tons could be made with less than one gram of plutonium and one kilogram of high explosive. A fusion bomb in which the three-to-five kilograms of plutonium in the primary trigger were replaced with one microgram of antihydrogen (the antimatter version of hydrogen) would be a virtually "clean" bomb because of the absence of fissile materials. Conceivably, such devices would not be characterised as weapons of mass destruction, allowing the advanced nuclear powers to keep preaching to weaker nations against building traditional "dirty" bombs. Because they do not contain a fission element - the current definition of a nuclear weapon - none of these weapons would breach the CTBT or the 1969 Non-Proliferation Treaty. Even a subcritical fissile explosive would not count.
Super-lasers, for example, are operating in the US, France, Britain, Germany, Japan and Russia. They are highly expensive, export-controlled technologies placed in national laboratories. The research is still at a scientific stage, and has many potential civilian uses including fusion power generation. But many scientists involved are acutely aware of the military applications. Indeed, a concerned group at Darmstadt University - home of the German super-laser program - published the Gsponer-Hurni paper. "These gadgets are not for terrorists, but for the governments of powerful countries," says Gsponer. For the likes of Germany and Japan, the new science is an insurance option to go straight to producing workable fusion weapons without testing. For the US, it promises a new level of unilateral strike power - against the alien enemies in their caves, or perhaps even against the crude missiles they lob against America's missile defence shield.
Hamish McDonald is the Herald's China correspondent
and former Foreign Editor.
Ian Mackenzie replied:First thoughts:
Detonating a fusion bomb with antimatter - um...
It's all down to how you keep the antimatter contained. As far as I know, there is no known compact way of keeping it contained for the months/years needed for "weaponising" the stuff.
But I suppose that if you surround the containment device with Tritium, and detonate explosives sufficiently symmetrically to have the energy release heat the Tritium (+ deuterium, Lithium Deuteride, whatever you prefer) to fusion temperatures (and keep it compressed for long enough to get a chain-reaction continuing), then it would work fine. On second thoughts, Lithium Deuteride might not be appropriate, as (from memory) the lithium only splits into Tritium etc when impacted by neutrons, and the matter-antimatter annihilation would produce mainly gamma rays (511keV for the electron-positron, ~1GeV for the nucleons), and the coupling of the antimatter to fusion reactions might not be as easy as expected.
Having read the article, The "sub-critical" fission bomb would still produce significant radionucleides, as well as local irradiation. Probably a more local spread of radioacive material, though. As for "less than a gram of plutonium and one kilogram of high explosive" producing a yield of several tons TNT equivalent - (calculations follow)
e= mc 2 = 21.4 kilotons per gram of mass fully converted to energy.
fission is less than 1% efficient at converting mass -> energy.
So, if you fission 1 gram, you get 214 tons TNT equivalent.
Last I heard, it took several kilos of U235 or Pu239 to get an explosive chain reaction happening. A complication is that (if I remember correctly) 10-15% of the neutrons are not emitted instantly; there is a significant delay - this lets nuclear power stations have a useful margin between controlled reaction rate & Chernoble. These neutrons are useless for bombs as they are only emitted after the fissionable material is no longer compressed.
All I'm saying is that if they can fission 10 micrograms (2 tons TNT equivalent) = 1% of the 1 gram of Pu239 with 1kg of explosive, they've got an awful lot better at compressing the Pu239 and keeping it compressed (and reflecting escaping neutrons back into the Pu) than they used to be.
Please read my thoughts with a suitable amount of salt (I'm not a nuclear physicist), but the second & third thoughts say that these ideas aren't as easy to make real as they sound, and the 1g of plutonium weapon sounds distinctly improbable.
