Nuclear weapons for anti-missile defense

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  • #26
Morbius
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Misinformation

. The test ban treaty and the obviously damaging consequences from high altitude nuclear explosions helped end that effort.
However, there is no practical effort ongoing, partly because of treaties, partly because Congress has prohibited new nuclear warhead development.
etudiant,

The above statements from your post above are incorrect. First, there's no such thing as "THE" test ban treaty; there are a number of test ban treaties. The "Partial Test Ban Treaty" prohibits atmospheric nuclear testing, that is exploding test nuclear weapons in the open air. However, that doesn't end development of nuclear-tipped interceptors, it just forces the testing to go underground which the USA did for 30 years. The second treaty is the "Threshold Test Ban Treaty". The TTBT prohibits test explosions, even underground, in excess of 150 kilotons. The final treaty is the "Comprehensive Test Ban Treaty" which prohibits all nuclear weapons testing. The CTBT was penned by the Clinton Administration, and President Clinton signed the CTBT in 1996. However, when Clinton submitted the CTBT for ratification by the Senate, the Senate failed to achieve the necessary 2/3 super-majority to make the CTBT binding on the USA. Additionally, the CTBT itself requires the adherence by all nuclear weapons capable countries ( a list of ~45 countries contained in the treaty ) before it can go into effect. Since the USA is naturally a nuclear weapons capable country, the failure of the USA to join the CTBT means that the CTBT treaty is NOT in effect for anybody; even those nations that completely ratified.

https://treaties.un.org/pages/ViewDetails.aspx?src=TREATY&mtdsg_no=XXVI-4&chapter=26&lang=en

Comprehensive Nuclear-Test-Ban Treaty
Not yet in force

Congress has NOT prohibited nuclear weapons development. A couple decades ago, Congress did prohibit development on low-yield nuclear warheads via the Spratt-Furse Law or "PLYWD" ( "plywood" ) law for Prohibition against Low Yield Weapons Development. However, the Spratt-Furse law was REPEALED in 2004.

There's NOTHING prohibiting the USA from developing new nuclear weapons should she so desire. It's simply a matter of choice or policy. The process of taking a new nuclear weapon design from the drawing board to finished production was started a few years ago for the Reliable Replacement Warhead or RRW. The RRW was a new warhead to replace aged warheads already in the stockpile. As per the decades old process, a competition in warhead design was held between Los Alamos (LANL) and Lawrence Livermore (LLNL) with LLNL being chosen the victor 7 years ago:

https://www.llnl.gov/str/May07/NewsMay07.html

The Department of Energy’s National Nuclear Security Administration (NNSA) announced that it has selected the design team from Lawrence Livermore and Sandia national laboratories to develop the reliable replacement warhead (RRW) for a portion of the nation’s sea-based nuclear deterrent. RRW is a joint NNSA–U.S. Navy program to ensure long-term confidence in a more secure, smaller, and safer nuclear weapons stockpile. NNSA and the Navy will work together to generate a detailed RRW project plan and cost estimate for developing and producing the system.
In 2006, the Nuclear Weapons Council approved the RRW concept as a feasible approach for sustaining the nation’s nuclear weapons stockpile. NNSA selected the Livermore–Sandia design because of the high confidence that it can be certified without underground nuclear testing. Several features of the design submitted by Los Alamos National Laboratory, also in partnership with Sandia, will be developed in parallel with the Livermore effort. As these features mature, they may be introduced into the warhead design as it progresses.

However, the Government decided not to pursue RRW to full production. The reliability and safety of the USA's nuclear stockpile is being maintained via "Life Extension Programs" (LEP). Rather than start with a clean sheet of paper; improvements and updates are incorporated into existing weapons. This has been successfully completed for LLNL's W87, for example:

https://str.llnl.gov/Mar12/obrien.html

In 2004, Lawrence Livermore successfully completed NNSA’s first LEP, refurbishing the W87. That effort enhanced the structural integrity of the warhead and extended its life by 30 years. For the W87, Livermore and Sandia scientists and engineers developed and certified the engineering design and worked closely with NNSA production facilities to ensure a cost-effective design and ease of manufacture. The W87 effort has served as a model for subsequent LEPs, including two being conducted by Los Alamos: the W76 warhead used in Trident II submarine-launched ballistic missiles (SLBMs) and the B61 family of nuclear bombs.

The above article is mostly about the W78 LEP for which LLNL was made lead lab in 2010, but President Obama recently decided to delay the W78 LEP for 5 years while the LEP for the B61 moves forward. However, the Nuclear Posture Review of 2010 issued by the Obama Administration as per law states:

http://www.defense.gov/npr/docs/2010 nuclear posture review report.pdf

The United States will study options for ensuring the safety, security, and reliability of nuclear warheads on a case-by-case basis, consistent with the congressionally mandated Stockpile Management Program. The full range of LEP approaches will be considered: refurbishment of existing warheads, reuse of nuclear components from different warheads, and replacement of nuclear components.

The USA hasn't developed any "new" nuclear warheads with a new "tail number" ( W87, W88, B61...) because it hasn't needed to. The LEP programs have been most successful in ensuring the capability and safety of the US nuclear arsenal without the need for "new" warheads, and this process will continue for the forseeable future. The USA might build a new nuclear warhead with a new "tail number" if backfitting capabilities into an existing weapon system would be too constraining. In that case, starting with a blank sheet of paper would be the cheaper solution.

Weapons development continues apace but using laboratory scale experiments integrated by computer simulation, rather than testing of full-scale systems. But to say that there is no development or that nuclear weapons work is prohibited by either treaty or Congress is just plain WRONG!

Some examples of ongoing nuclear weapons development:

Plutonium at 150 years: Going Strong and Aging Gracefully
https://str.llnl.gov/Dec12/chung.html

Enhancing Confidence in the Nation's Nuclear Stockpile
https://str.llnl.gov/JulAug10/allen.html

A CAT Scanner for Nuclear Weapon Components
https://str.llnl.gov/JulAug09/allen.html

Monitoring a Nuclear Weapon from the Inside
https://www.llnl.gov/str/JulAug08/trebes.html

Greg
 
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  • #27
etudiant
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etudiant,

The above statements from your post above are incorrect. .

Weapons development continues apace but using laboratory scale experiments integrated by computer simulation, rather than testing of full-scale systems. But to say that there is no development or that nuclear weapons work is prohibited by either treaty or Congress is just plain WRONG!


Thank you, Morbius, for correcting my broad brush assertion with a much more nuanced and detailed summary of the current state of nuclear weapon development in the US.

Clearly the net result is still that whether because of treaty or domestic political consensus, nuclear weapons development in the US has ceased. Stockpile integrity assurance is ongoing, but not new weapons design. The possibility of nuclear shaped charges for instance, which would allow even very deeply buried targets to be held at risk, is left unexplored, as is the potential for nuclear devices that can function without a a-bomb trigger.
Imho, the retreat from aggressive nuclear research has robbed the country of the knowledge and skills needed to effectively address current problems, notably our energy situation, while wasting our most educated technical talents rebuilding museum pieces. Even worse, the country does not even have the offsetting advantage of a solid global nuclear test ban treaty in exchange for this silliness, something most Americans, are probably as little aware of as I was before I read your contribution.
 
  • #28
Morbius
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Clearly the net result is still that whether because of treaty or domestic political consensus, nuclear weapons development in the US has ceased. Stockpile integrity assurance is ongoing, but not new weapons design. The possibility of nuclear shaped charges for instance, which would allow even very deeply buried targets to be held at risk, is left unexplored, as is the potential for nuclear devices that can function without a a-bomb trigger.
Imho, the retreat from aggressive nuclear research has robbed the country of the knowledge and skills needed to effectively address current problems, notably our energy situation, while wasting our most educated technical talents rebuilding museum pieces.
etudiant,

I would have to strongly disagree with your contention that nuclear weapons development has ceased, as well as your characterization that the weapons scientists are "rebuilding museum pieces".

An instructive analogy would be to look at the current and past offerings of airliners from their manufacturer Boeing. I would ask that you compare the Boeing 737-100 model first built in 1966 to the current Boeing 737-900ER. The Boeing 737-100 had low-bypass P&W JT8D engines with 14,500 lbs of thrust, while the Boeing 737-900ER has modern high-bypass turbofans engines, the CFM56-7 series with 27,300 lbs of thrust.

If you looked into the cockpit of a Boeing 737-100, you would see 1960s vintage avionics with analog gauges. If you look into the cockpit of a Boeing 737-900ER, you would see a 21st century "glass cockpit" with digital display screens and advanced 21st century avionics which resemble what one would see in the latest Boeing 777 and Boeing 787 models.

The Boeing 737-100 has 650 cubic feet of cargo capacity, while the Boeing 737-900ER has 1,835 cubic feet. The range of the Boeing 737-100 was 1540 nautical miles while the Boeing 737-900ER has a range of 5,510 nautical miles.

All in all; the Boeing 737-900ER is a VERY DIFFERENT and MUCH MORE ADVANCED aircraft than is the Boeing 737-100; yet they are both members of the Boeing 737 family. Boeing didn't change the family number, but that's about all they didn't change.

The Boeing 737-900ER is every bit as modern an aircraft as its Boeing 777 stablemates. Do you really think one could intelligently characterize a Boeing 737-900ER as a "rebuilt museum piece 737"? I wouldn't think so.

Your statement about "nuclear shaped charges" demonstrates that you understand very little about shaped charges as well as nuclear explosives. LLNL which designs nuclear weapons, also designs coventional shaped charges as used in military weapons. Here's an article from LLNL that can give you some background:

https://www.llnl.gov/str/Baum.html

One doesn't need shaped charge technology to attack deeply buried targets with nuclear warheads. The shaped charge approach really isn't appropriate or needed. The nuclear weapons designer has various techniques to "couple" the blast into a shockwave in the ground material, and that shockwave will take care of destroying deeply buried targets. For example, consider the B61-11:

http://www.globalsecurity.org/wmd/systems/b61-11.htm

The B61-11 can penetrate and detonate below the earth's surface, creating a massive shock wave capable of destroying underground targets. In tests the bomb penetrates only 20 feet into dry earth, even when dropped from altitudes above 40,000 feet. But even this shallow penetration before detonation allows a much higher proportion of the explosion to transferred into ground shock relative to a surface burst.

I also wouldn't lump the current R&D efforts in the area of nuclear weapons in with the R&D efforts for energy research into one "zero sum game" and imply that efforts in the weapons arena neccessarily detracts from efforts in energy research.

In fact, the nuclear weapons research and nuclear energy research are carried out at separate laboratories, managed by differing parts of DOE, and with different budgets. For example, nuclear weapons research is carried out by Los Alamos and Lawrence Livermore national laboratories, which are managed by the National Nuclear Security Agency (NNSA) in the Dept. of Energy using funds allocated by Congress for the nuclear weapons mission. Nuclear reactor and nuclear energy research was carried out by Argonne and Oak Ridge national laboratories, managed by the DOE Office of Science with funds allocated by Congress for energy R&D.

The action that really killed the Government's nuclear energy R&D was when the Clinton Administration terminated the Integral Fast Reactor (IFR) work at Argonne National Lab back in 1994 as detailed in this 1998 interview with Argonne Associate Director, Dr. Charles Till:

http://www.pbs.org/wgbh/pages/frontline/shows/reaction/interviews/till.html

The decision was made in the early weeks of the Clinton administration. It was tempered somewhat in the Department of Energy in that first year. Congress then acted to keep the program alive in that first year. And then in the second year of the Clinton administration, the decision to really reinforce the earlier decisions was made final, and the Administration put a very considerable effort into assuring successfully that the IFR would be canceled.

and

Let me answer the question this way. Nuclear power for very many years was not a party proposition. There was bipartisan support for the development of nuclear power. That changed in and around the 1976. It was certainly changed dramatically during the Carter Administration, from '76 to '80. The Reagan administration was supportive of nuclear power development, but not madly so. They supported a continued effort, probably at a level of something like 10 or 20% of the effort that had been carried out in the country a decade or so before. That was also true of the Bush administration. The Clinton administration, I think, firmed up quite an anti-nuclear power position. The position of the administration is that present day reactors are supported, but that there is no need for any further nuclear reactor development or improvement. And the implications of that are that nuclear power then will be a passing thing.

President Clinton made good on his campaign promise to the anti-nuclear wing of the Democratic Party to terminate "unneccessary" nuclear energy research. When one does that, one devastates the scientific infrastructure that had been built up over the preceeding decades. If you terminate the research for even one year, you destroy the infrastructure since the scientists that the USA painstakingly assembled in laboratories such as Argonne had to disband and go find jobs elsewhere. Even if the minority party were able to reconstitute the funding the next year; that doesn't mean it reconstitutes the program. The disbanded scienctists aren't going to come back with no guarantee that they won't be out of jobs the next year.

Scientists and engineers used to be able to go to work in the federally-funded R&D enterprise of the DOE national laboratories, or NASA, or any of a number of defense and civillian contractors, as well as Universities; and those scientists could count on spending a career advancing their profession.

Now it seems that the scientists and engineers who are the "seed corn" for our evolving development are the first thing the politicians cut off when money gets tight. They also expect that scientists can work on the newest "fad" that fits the politician's fancy. If last year's fad was solar power and this year's fad is wind turbines, and next year's fad is geothermal; then it's all the same to the politicians, if they even support it at all.

Rather than support scientists and engineers, which I would consider as investing in the future of the Nation, the politicians prefer to give money away as a more efficient way of buying the votes that the politicians so ravenously desire.

Believe me; nuclear weapons research and defense development are NOT the reason for the lack of energy research.

Greg
 
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  • #29
etudiant
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Not to belabor a topic where I suspect we are in broad agreement, I'd just note that the idea of a nuclear shaped charge, basically a directed nuclear blast, was broadly hinted at by the late Ted Taylor in the book 'The curve of binding energy' that John McPhee wrote about him.
I'm well aware of the performance evolution of commercial jet transports and imho that same kind of performance improvement is explicitly ruled out as an objective in the US nuclear program under the Stockpile Stewardship concept. That also makes it harder to attract or encourage bright people to work there.
I agree entirely with your perspective that the US has deliberately squandered much of its technical seedcorn and manufacturing expertise for the basest of political motives and that nuclear weapons research is just another area where this decay is manifest.
 
  • #30
Morbius
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Not to belabor a topic where I suspect we are in broad agreement, I'd just note that the idea of a nuclear shaped charge, basically a directed nuclear blast, was broadly hinted at by the late Ted Taylor in the book 'The curve of binding energy' that John McPhee wrote about him.
etudiant,

If you think about it, you will realize that the degree to which one can "direct" the shape of the nuclear explosion is to a far lesser degree than a chemical explosion because the "Q", the energy release of the reaction is so much greater for a nuclear explosion than a chemical explosion. The Q energy release is released isotropically, and the system, in essence, doesn't "remember" a direction.

For example, consider the scatter of a neutron off a light nucleus in comparison to the neutron-induced fission of a heavy nucleus. The scatter off the light nucleus can be significantly anisotropic because the system essentially "remembers" which direction the incident neutron was travelling. However, in the case of the fission, so much reaction energy is released isotropically that it "swamps" the incident energy of the neutron, and the fission reaction can be considered for all intents and purposes as isotropic.
I'm well aware of the performance evolution of commercial jet transports and imho that same kind of performance improvement is explicitly ruled out as an objective in the US nuclear program under the Stockpile Stewardship concept. That also makes it harder to attract or encourage bright people to work there.
That is where you are 100% WRONG. It's EXACTLY analogous to the case of the evolution of commercial jet transports. Contrary to your ill-informed statements, the objectives of the Stockpile Stewardship Program does NOT rule out design changes. The goals of the program are to cease nuclear testing, but NOT needed / desired design changes. The legislation that establishes the Stockpile Stewardship program makes NO references to your supposed prohibitions and ill-founded claims that objectives have been "explicitly ruled out" stated above:

http://www.law.cornell.edu/uscode/text/50/2521?qt-us_code_tabs=0#qt-us_code_tabs

The Secretary of Energy, acting through the Administrator, shall establish a stewardship program to ensure—

(1) the preservation of the core intellectual and technical competencies of the United States in nuclear weapons, including weapons design, system integration, manufacturing, security, use control, reliability assessment, and certification; and

(2) that the nuclear weapons stockpile is safe, secure, and reliable without the use of underground nuclear weapons testing.

The Nuclear Posture Review, which is the policy statement for nuclear weapons work states that ALL options are on the table, there's no prohibition. The USA doesn't design "new" warheads because it doesn't need to. The USA hasn't fielded a new delivery vehicle for some time. If that changes, for example, the US Navy is already looking at a follow-on to the Trident fleet ballistic missile submarines. If the US Navy desires new missiles to go along with their new submarines, then there may be a need for new nuclear warheads. Until then, there is PLENTY of very challenging work for bright people to work on.

Since you are essentially totally clueless on the subject; please refrain from making the pretense that you are informed, and don't mislead the denizens of the forum with false information.

Greg
 
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  • #31
etudiant
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etudiant,
Since you are essentially totally clueless on the subject; please refrain from making the pretense that you are informed, and don't mislead the denizens of the forum with false information.

Greg
Apart from aerospace, I make no claim to be informed beyond what I read in the news media and in the reports of congressional hearings.
Those sources have repeatedly stated that the Stewardship program is aimed to ensure the continued effectiveness of the US nuclear arsenal, not at improving its performance. The 2008 decision to abandon the Reliable Replacement Warhead program supports that view.
I would be thrilled to learn that the US has a vigorous and innovative nuclear energy initiative under way, but do not see substantial evidence of such an effort.
 
  • #32
Morbius
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Apart from aerospace, I make no claim to be informed beyond what I read in the news media and in the reports of congressional hearings.
Those sources have repeatedly stated that the Stewardship program is aimed to ensure the continued effectiveness of the US nuclear arsenal, not at improving its performance. The 2008 decision to abandon the Reliable Replacement Warhead program supports that view. .
etudiant,

100% WRONG AGAIN One of the provisions that authorized the development of the RRW was that it provided "no new military capability". The RRW was cancelled purely on political grounds; it was cancelled in 2007 when Nancy Pelosi became Speaker of the House, and no further provisions for funding RRW could be passed with Nancy Pelosi as Speaker. When Boehner became Speaker in 2011, the new Impediment became the President.

Evidently you harbor the mistaken idea that the purpose of the redesign / LEP process is to "improve performance". That is just NOT true - the purpose is to maintain the performance and safety.

Let me refer you to the following from the Associate Director of Lawrence Livermore responsible for the nuclear weapons program:

https://str.llnl.gov/Mar12/comMar12.html

WHEN the weapons comprising our nuclear forces of deterrence were originally designed decades ago, scientists knew the warheads could not remain safe, secure, and reliable indefinitely. Over time, components and materials deteriorate as the weapons age. As a result, the nuclear design laboratories—Lawrence Livermore, Los Alamos, and Sandia national laboratories—continually assess the health of the stockpile and determine whether a particular weapon type needs to undergo a life-extension program (LEP).

LEP efforts include identifying and correcting potential technical issues by refurbishing or replacing certain components. LEPs also allow us to strengthen existing safety systems, for example, by introducing insensitive high explosives, which are more resistant than conventional high explosives to detonation from fire or accident.

LEPs are an important tool that allows us to seamlessly sustain the nation’s nuclear weapons. In effect, LEPs are triumphs of the National Nuclear Security Administration’s (NNSA’s) Stockpile Stewardship Program, which was launched at the end of the Cold War to maintain our weapons without nuclear testing. Advances in science, engineering, and computing—representing everything we have learned about nuclear reactions and materials science for the past 70 years—are incorporated into LEP efforts to ensure the devices remain safer, more secure, more reliable, longer-lived, and more maintainable than ever.

Dr. Goodwin says it in the first paragraph of his commentary, that the nuclear weapons would not remain safe and reliable indefinitely.

Again, let me explain this in terms of an analogy. Have you ever heard of dynamite becoming "tender"? Dynamite was invented by Alfred Nobel, the founder of the Nobel Prize. Nobel made his fortune by solving a major industrial problem, which was that high-explosives like nitro-glycerin were extremely "touchy" and hard to handle. The "touchy" nature of "nitro" is legendary. Nobel found that if you mixed "nitro" with sawdust or a type of clay called "diatomaceous earth"; the mixture was more stable and easier to handle; but could still be detonated on command with Nobel's "blasting cap".

Unfortunately, dynamite didn't stay stable and safe to handle indefinitely. As dynamite aged, the "nitro" tends to separate from the sawdust or clay. You end up with a stick that has little pools of "nitro" or the "nitro" leeches into the paper wrapper. Once again, you have small volumes of pure "nitro" and that "nitro" is susceptible to shocks and bumps, and can be extremely dangerous to handle. If the dynamite is shocked or bumped, the little pools of liquid "nitro" can explode just as easily as if you had pure "nitro" because that is what you have, pure liquid "nitro". The explosion of that bit of "nitro" will then propagate and set off the explosion of the whole stick of dynamite. Essentially, the dynamite becomes as dangerous to handle as the original "nitro" from which it is made. When dynamite ages to this degree, it is called "tender".

http://en.wikipedia.org/wiki/Dynamite

Over time, the dynamite will "weep" or "sweat" its nitroglycerin, which can then pool in the bottom of the box or storage area. (For that reason, explosive manuals recommend the repeated turning over of boxes of dynamite in storage.)

If someone took dynamite that is approaching the dangerous "tender" stage and remixed and reformed the dynamite to reestablish its stable properties; would you call that "improving the performance" of the explosive? It's not improving on the explosive; it's reestablishing the safety margins that one had when the dynamite was first made.

In essence, the redesign / LEP process is NOT for improving performance; but to address problems that develop as the weapon ages, and even enhance the safety over the original specs. Note where Dr. Goodwin states, LEPs also allow us to strengthen existing safety systems, for example, by introducing insensitive high explosives, which are more resistant than conventional high explosives to detonation from fire or accident.

You seem to be stuck in this mindset that changes / modifications / redesign of nuclear weapons must be for the sole purpose of "improving the performance" ( "making a bigger bang" ). However, Dr. Goodwin's commentary above shows that not to be the reasoning. It is about sustaining the level of safety and reliability; or as the first sentence of the last paragraph of the quote above states:

LEPs are an important tool that allows us to seamlessly sustain the nation’s nuclear weapons

Greg
 
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  • #33
etudiant,

If you think about it, you will realize that the degree to which one can "direct" the shape of the nuclear explosion is to a far lesser degree than a chemical explosion because the "Q", the energy release of the reaction is so much greater for a nuclear explosion than a chemical explosion. The Q energy release is released isotropically, and the system, in essence, doesn't "remember" a direction.

For example, consider the scatter of a neutron off a light nucleus in comparison to the neutron-induced fission of a heavy nucleus. The scatter off the light nucleus can be significantly anisotropic because the system essentially "remembers" which direction the incident neutron was travelling. However, in the case of the fission, so much reaction energy is released isotropically that it "swamps" the incident energy of the neutron, and the fission reaction can be considered for all intents and purposes as isotropic.
IIRC at the temperatures involved (upwards of 100 million degrees) a large fraction of released energy exists in the form of photons (X-rays) - and those can be easily made to exit the casing anisotropically, by providing radiation windows with desired shapes.
 
  • #34
Morbius
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IIRC at the temperatures involved (upwards of 100 million degrees) a large fraction of released energy exists in the form of photons (X-rays) - and those can be easily made to exit the casing anisotropically, by providing radiation windows with desired shapes.
nikkom,

Only for an extremely short time. If, say you want to make a radiation beam that goes "downward", and you want to accomplish this by providing a metal casing that inhibits the radiation from going left / right, front / back or upwards; then in order for the casing to inhibit the radiation from going in those directions, it has to absorb that radiation. However, there's so much energy in a nuclear weapon that within an extremely short time, that casing will be heated to a plasma that can no longer absorb the radiation.

So your idea doesn't really work.

Greg
 
  • #35
nikkom,

Only for an extremely short time.
Extremely short time is not a problem. X-rays move with the speed of light. That's very, very fast: 30 cm/nanosecond. Even if X-ray photon on average needs dozens of reflections before it finds the radiation window, it still takes just a few nanoseconds.

So, how many nanoseconds do we have?

If, say you want to make a radiation beam that goes "downward", and you want to accomplish this by providing a metal casing that inhibits the radiation from going left / right, front / back or upwards; then in order for the casing to inhibit the radiation from going in those directions, it has to absorb that radiation. However, there's so much energy in a nuclear weapon that within an extremely short time, that casing will be heated to a plasma that can no longer absorb the radiation.
The plasma does not need to absord the radiation. It is sufficient to reflect it. If the casing is made of high-Z materials, the plasma will stay opaque to the X-rays: they will be strongly scattered off it. This also means that not the entire casing turns to plasma at once - its inner few millimeters do so first, and then this plasma shields the rest for a short time.

That's exactly how second stage of fusion device works: high-Z lined casing keeps a "sea" of X-rays contained, so that they are used to ablatively compress the secondary. It works: radiation manages to compress the secondary before casing "burns through".

Nwfaq3 contains the following example:

"For example, after 100 nanoseconds at 2 KeV [~23 million K] the wave will have penetrated to a depth of 0.27 centimeters [of uranium]."

IOW: with reasonably thick casings (less than 1 cm) it is possible to contain X-rays long enough (hundreds of nanoseconds) for them to escape through radiation windows.
 
  • #36
Morbius
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Extremely short time is not a problem. X-rays move with the speed of light. That's very, very fast: 30 cm/nanosecond. Even if X-ray photon on average needs dozens of reflections before it finds the radiation window, it still takes just a few nanoseconds.

So, how many nanoseconds do we have?
nikkom,

You tell me. You are the one that wants an anisotropic source. I'm just saying that since any anisotropy is going to be extremely short lived, then for all intents and purposes, it didn't happen

The plasma does not need to absord the radiation. It is sufficient to reflect it. If the casing is made of high-Z materials, the plasma will stay opaque to the X-rays: they will be strongly scattered off it. This also means that not the entire casing turns to plasma at once - its inner few millimeters do so first, and then this plasma shields the rest for a short time.
100% WRONG!!! You don't get to decide whether the X-rays and gamma rays are going to reflect or be absorbed, Mother Nature makes that decision. Unfortunately for your hypothesis, reflection is a collective phenomenon of multiple atoms. However, the wavelengths of the high energy X-rays and gamma rays are too short; . That's why we don't have X-ray and gamma-ray mirrors modulo some relatively weak reflection at grazing angles for low energy X-rays.

TOTALLY 100% WRONG about the plasma "shielding". I can see you've NEVER studied plasma physics.
That's exactly how second stage of fusion device works: high-Z lined casing keeps a "sea" of X-rays contained, so that they are used to ablatively compress the secondary. It works: radiation manages to compress the secondary before casing "burns through".
Yes - I know how that works.
Gregory
 
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  • #37
nikkom,

You tell me. You are the one that wants an anisotropic source. I'm just saying that since any anisotropy is going to be extremely short lived, then for all intents and purposes, it didn't happen
I told it already. With 0.5 cm thick high-Z casing, we have several hundreds of nanoseconds before casing stops containing X-ray "photon soup".

100% WRONG!!! You don't get to decide whether the X-rays and gamma rays are going to reflect or be absorbed, Mother Nature makes that decision. Unfortunately for your hypothesis, reflection is a collective phenomenon of multiple atoms. However, the wavelengths of the high energy X-rays and gamma rays are too short; . That's why we don't have X-ray and gamma-ray mirrors modulo some relatively weak reflection at grazing angles for low energy X-rays.
There is no need to shout.

I didn't mean reflection as in a mirror. Scattering and re-radiation will do. And *it does* in the fusion device. High-Z plasma is opaque to X-rays. They get absorbed and re-radiated by it, impeding radiative energy transfer through casing.

TOTALLY 100% WRONG about the plasma "shielding". I can see you've NEVER studied plasma physics.
And also, each and every fusion bomb test is a fake. Right...
 
  • #38
Morbius
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I told it already. With 0.5 cm thick high-Z casing, we have several hundreds of nanoseconds before casing stops containing X-ray "photon soup".
nikksom,

Sorry - but your "calculation" is WAY, WAY TOO SIMPLISTIC. The physics is much more complex.
I didn't mean reflection as in a mirror. Scattering and re-radiation will do.
Scatter and re-radiation are NOT reflection. Heck you don't even know the vocabulary let alone how to do detailed calculations and simulation. When scientists mean scatter and re-radiation, they call it "scatter" and "re-radiation" and not "reflection".
And *it does* in the fusion device. High-Z plasma is opaque to X-rays. They get absorbed and re-radiated by it, impeding radiative energy transfer through casing.
This is where you don't know your plasma physics. High-Z solids are opaque, as are plasmas that have been compressed above what is called the "critical density". But EM radiation goes through plasma below the critical density. That's why I said it will only work the way you "think" it is going to work for an extremely short time. Not all the energy is re-radiated; and the energy that is not re-radiated is absorbed and turns the material from a high-Z solid to a high-Z low-density plasma that no longer has high opacity.

Enhanced x-ray emissions from low-density high-Z mixture plasmas generated with intense nanosecond laser

http://www.sciencedirect.com/science/article/pii/S0375960114000760

I would also recommend the classic text "Phyics of Fully Ionized Gases" by Lyman Spitzer.
And also, each and every fusion bomb test is a fake. Right...
By what stretch of "logical" reasoning did you come up with THAT????

Instead of discussing large "nuclear devices"; let's look at another topic which is ICF - Inertial Confinement Fusion. The re-radiation idea you espouse above is used in ICF. For example, I refer you to this Wikipedia entry:

http://en.wikipedia.org/wiki/Hohlraum

The indirect drive approach to inertial confinement fusion is as follows; the fusion fuel capsule is held inside a cylindrical hohlraum. The radiation source (e.g., laser) is pointed at the interior of the hohlraum, which absorbs and re-radiates the energy as X-rays, rather than on the capsule itself, a process known as indirect drive. The advantage to this approach is that the energy is re-radiated in a much more symmetric fashion than would be possible in the direct drive approach, resulting in a more uniform implosion.

The X-ray intensity around the capsule must be very symmetrical to avoid hydrodynamic instabilities during compression.

Gregory
 
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  • #39
nikksom,

Sorry - but your "calculation" is WAY, WAY TOO SIMPLISTIC. The physics is much more complex.
Okay. You are a specialist here, please start using numbers. I, a layman, already gave some numbers in my posts. Tell me which of my numbers are wrong. Give yours.

> And *it does* in the fusion device. High-Z plasma is opaque to X-rays. They get absorbed and re-radiated by it, impeding radiative energy transfer through casing.

This is where you don't know your plasma physics.
Indeed I'm not plasma physicist. However, I do know that fusion bombs use radiation implosion, that radiation for that purpose is contained by high-Z lined casing. It's public knowledge now. Am I wrong about that?

High-Z solids are opaque, as are plasmas that have been compressed above what is called the "critical density". But EM radiation goes through plasma below the critical density. That's why I said it will only work the way you "think" it is going to work for an extremely short time. Not all the energy is re-radiated; and the energy that is not re-radiated is absorbed and turns the material from a high-Z solid to a high-Z low-density plasma that no longer has high opacity.
Numbers please. How many nanoseconds plasma needs to expand to transparency after it gets heated by X-rays? I'm not asking you to reveal any secrets. Data from publicly-available sources such as NWFAQ will suffice.
 
  • #40
Morbius
Science Advisor
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Okay. You are a specialist here, please start using numbers. I, a layman, already gave some numbers in my posts. Tell me which of my numbers are wrong. Give yours.

Indeed I'm not plasma physicist. However, I do know that fusion bombs use radiation implosion, that radiation for that purpose is contained by high-Z lined casing. It's public knowledge now. Am I wrong about that?

Numbers please. How many nanoseconds plasma needs to expand to transparency after it gets heated by X-rays? I'm not asking you to reveal any secrets. Data from publicly-available sources such as NWFAQ will suffice.
nikkom,

I am not commenting on anything in the NWFAQ.

I'm just saying that you aren't going to have some high-Z material stay opaque for 100 nanoseconds or more to provide your radiation "beam". In very short order, that is on very short time scales much, much less than your 100 nanoseconds ( 0.1 microsecond ); your high-Z material is going to be a low-density plasma that won't do what you think it is going to do.

Gregory
 
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  • #41
nikkom,

I can't comment on ANYTHING; even information that has been publicly released. I can't comment on anything in the NWFAQ.

I'm just saying that you aren't going to have some high-Z material stay opaque for 100 nanoseconds or more to provide your radiation "beam".
Okay. The numbers for fusion device I learned from public sources:

* generation of X-rays in 1st (fission) stage: ~50 nanoseconds.
* arrival of X-rays, thermalization of tamper and casing surface: 10 ns.
(As I told it before: X-rays move very fast!)
* ablative compression of the tamper and fusion fuel: 200-500 ns.
(you say it is impossible to contain X-rays for 100 ns)
* fusion burn: 20 ns.

It can be done. It *has been* done.

Compared to the above, our task doesn't even require X-rays to be contained for hundreds of nanoseconds. It appears the shape-forming casing needs to survive for only 10 ns or so.
 
  • #42
Morbius
Science Advisor
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Okay. The numbers for fusion device I learned from public sources:

* generation of X-rays in 1st (fission) stage: ~50 nanoseconds.
* arrival of X-rays, thermalization of tamper and casing surface: 10 ns.
(As I told it before: X-rays move very fast!)
* ablative compression of the tamper and fusion fuel: 200-500 ns.
(you say it is impossible to contain X-rays for 100 ns)
* fusion burn: 20 ns.

It can be done. It *has been* done.

Compared to the above, our task doesn't even require X-rays to be contained for hundreds of nanoseconds. It appears the shape-forming casing needs to survive for only 10 ns or so.
nikkom,

In ICF, the fusion fuel is compressed by the X-rays from the laser drive.

Is the time it takes the fuel to move so that it is compressed necesarily equal to the time that the drive acts on the fuel?

Suppose I am playing baseball, and it takes 20 seconds for the ball that I hit to travel from home plate where I hit it, out to the left field foul post where it strikes the post. From that information, can we then conclude that the bat was in contact with the ball for 20 seconds when it got hit.
( Suppose I'm saying that it is impossible for the bat to maintain contact with the ball for 10 seconds )

That is EXACTLY the assumption you've made above when you compare compression times to the time that radiation is contained.

Gregory
 
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  • #43
18
1
In the early 60s, before the PTBT went into effect, the Soviets did a number of such tests; they were wild about throwing their primitive missiles of the time up in trajectories of thousands of miles across their own territory, ending in nuclear blasts above Kazakhstan and Novaya Zemlya. The chief object was developing anti-missile technology. No other country (US included) ever played that loose. Only one time did the Soviets mess up - the test known as K-3 didn't make it to its intended target but exploded high over central Kazakhstan, and caused widespread EMP damage on the ground, reportedly burning down a power generation station.
 

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