Nuclear weapons for anti-missile defense

[lavinia]

I couldn't find an compatible heading for this question and decided to place it here since it deals with nuclear engineering, sort of.

From the documentary movie, Trinity and Beyond, which is a history of the American nuclear weapons program, it seems that high atmosphere nuclear detonations were tested for anti missile and anti-bomber defence. Incoming missiles from the Soviet Union would be destroyed in transit by high altitude thermo-nuclear blasts. As soon as the enemy missiles were detected, nuclear tipped missiles would be launched to destroy them

Does this technology work? Why wouldn't one use it instead of Star Wars technology?

Also it seems that testing was done to created a radioactive debris shield in space that would disable incoming missiles. Why wouldn't this work?

 

[a_potato]

Nuclear explosions in the atmosphere are bad

 

[SteamKing]

This article on the Nike program should answer your questions:

http://en.wikipedia.org/wiki/LIM-49_Nike_Zeus

Setting off a lot of 400 KT warheads overhead doesn't do anybody much good.

 

[nikkkom]

Does this technology work? Why wouldn't one use it instead of Star Wars technology?

It works. Sorta kinda. It is obviously not practical to perform a full-scale test of it, though (think of the fallout).
E.g. how much EMP will this generate? Will radars still function and be able to track next wave of ICBMs to intercept?

Also it seems that testing was done to created a radioactive debris shield in space that would disable incoming missiles. Why wouldn't this work?

I think you are mistaken. Such shield needs to be incredibly dence to be able to affect incoming missiles in any way - tens of thousands of nukes at least. I don't think there ever was such a plan.

 

[Astronuc]

Nuclear explosions in the atmosphere are bad

Yes - adding fission products and activated elements (radionuclides/fallout) to the environment is generally considered undesirable.

 

[lavinia]

I think you are mistaken. Such shield needs to be incredibly dence to be able to affect incoming missiles in any way - tens of thousands of nukes at least. I don't think there ever was such a plan.

Maybe so although the idea was mentioned in the documentary so it was certainly considered at least as an idea.

 

[lavinia]

It works. Sorta kinda. It is obviously not practical to perform a full-scale test of it, though (think of the fallout).
E.g. how much EMP will this generate? Will radars still function and be able to track next wave of ICBMs to intercept?

The link that SteamKing gave gives a sort a kinda answer as well. It seems that MIRV's were a big deterrent to the deterrent and the system was eventually abandoned for cost and doubt about its viability. Edward Teller for instance argued that it would be cheaper to get around the system than to develop it.

 

[lavinia]

Yes - adding fission products and activated elements (radionuclides/fallout) to the environment is generally considered undesirable.

This is really an aside but the documentary said that over three hundred nuclear tests were done. What then was the actual fallout - so to speak - of all of these tests?

 

[a_potato]

This is really an aside but the documentary said that over three hundred nuclear tests were done. What then was the actual fallout - so to speak - of all of these tests?

The effect of fallout is time dependent. After a long time the radionuclides decay to much less active isotopes, and in doing so release all sorts of nasties. You could probably estimate the total dose inflicted on the planet give or take an order of magnitude...

 

[SteamKing]

From the Nevada Test Site (north of Las Vegas), the fallout from the atmospheric tests there was caught by the prevailing winds and deposited over the eastern and central portions of the continental US. The atmospheric tests performed in the Pacific atolls produced fallout which largely was dispersed over water, except for a few incidents (like the early H-bomb tests) where fallout contaminated a Japanese fishing fleet and some nearby inhabited islands.

 

[Morbius]

The effect of fallout is time dependent. After a long time the radionuclides decay to much less active isotopes, and in doing so release all sorts of nasties. You could probably estimate the total dose inflicted on the planet give or take an order of magnitude...

a_potato,

The following table courtesy of the Health Physics Society chapter at the University of Michigan gives the comparison of how much dose is due to fallout from nuclear testing vis-a-vis other source:

http://www.umich.edu/~radinfo/introduction/radrus.htm

Fallout is <0.03% of the background dose. Mother Nature gives you over 3000X the dose as does fallout.

Greg

 

[SteamKing]

I couldn't find an compatible heading for this question and decided to place it here since it deals with nuclear engineering, sort of.

From the documentary movie, Trinity and Beyond, which is a history of the American nuclear weapons program, it seems that high atmosphere nuclear detonations were tested for anti missile and anti-bomber defence. Incoming missiles from the Soviet Union would be destroyed in transit by high altitude thermo-nuclear blasts. As soon as the enemy missiles were detected, nuclear tipped missiles would be launched to destroy them

Does this technology work? Why wouldn't one use it instead of Star Wars technology?

Also it seems that testing was done to created a radioactive debris shield in space that would disable incoming missiles. Why wouldn't this work?

At the time that these tests were made, microelectronics were in their infancy and not very widespread. Vacuum tubes were still very common in radios, televisions, avionics, etc. High altitude nuclear detonations produce electromagnetic pulses (EMP), which fry unshielded microcircuits but which leave vacuum tubes unaffected. If you were to make a modern nuclear weapons defensive systems using high-altitude nuclear explosions, all computers and other systems dependent on microelectronics would have to be shielded against EMP or risk destruction.

 

[etudiant]

The initial ABM nuclear warheads were very large, in the 2-5 megaton class, presumably because the intercept accuracy was low. The test ban treaty and the obviously damaging consequences from high altitude nuclear explosions helped end that effort. The explosion effects help blind the guidance radars for subsequent missiles, which undermines the defense effort.
It is probable that the research labs are considering what could be done using much smaller nukes instead of the current 'hit to kill' warheads. A tiny nuke, say a kiloton, would be a very effective anti missile weapon with much less self impact. However, there is no practical effort ongoing, partly because of treaties, partly because Congress has prohibited new nuclear warhead development.

 

[lavinia]

I found this link.

http://www.foreignaffairs.com/artic...-daryl-g-press/the-rise-of-us-nuclear-primacy

 

[analogdesign]

This technology was implemented in 1980 http://en.wikipedia.org/wiki/Missile_Command

Unfortunately, extensive simulations all ended with the destruction of the United States.

SteamKing: Here is an awesome documentary about the Bell Labs Sentinel ABM System.
http://www.youtube.com/watch?v=ARx2-wRn9-Y

 

[sparkle_pony]

hahaha analogdesign;

I think the problem of EMP, fallout, and radar blinding is probably overestimated. The first two effects are relatively localized: EMP is subject to the inverse square law and fallout, as another poster pointed out, of a single nuclear event would hardly register above background. Radar blinding can be mitigated, in part, with distributed sensors and diversified bandwidths.

In the Nike Zeus program a nuclear warhead was used to make up for lack of targeting precision. Once hit-to-kill kinetic interceptors were proven there was no longer an incentive to use nuclear warheads; the kinetic interceptors were far cheaper.

 

[SteamKing]

hahaha analogdesign;

I think the problem of EMP, fallout, and radar blinding is probably overestimated. The first two effects are relatively localized: EMP is subject to the inverse square law and fallout, as another poster pointed out, of a single nuclear event would hardly register above background. Radar blinding can be mitigated, in part, with distributed sensors and diversified bandwidths.

In the Nike Zeus program a nuclear warhead was used to make up for lack of targeting precision. Once hit-to-kill kinetic interceptors were proven there was no longer an incentive to use nuclear warheads; the kinetic interceptors were far cheaper.

Yes, but the OP asked why nuclear warheads weren't being used for ABM defense. And, it's unlikely that an attack would involve the interception of just one missile; after all, modern strategic missiles are equipped with multiple re-entry vehicles which ALL have to be destroyed in order to prevent any nuclear hits.

When atmospheric testing of nuclear devices was still permitted, several different atomic devices were detonated to gather data about the extent and damage the EMP could cause. As a result f these tests, military aircraft and naval vessels receive special hardening against the effects of EMP so that vital communications and other electronic systems remain operational in the event that an atmospheric nuclear blast is encountered.

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

Because of various factors, it is hard to predict what the effect of EMP, fallout, and radiation will have on ground- and air-based systems, which is why these systems may be over-designed.

 

[sparkle_pony]

True but if the MIRVs were deployed early they would have spread out enough to require multiple interceptors, nuke or not.

For EMP I don't doubt the problem, just the range. If the intercept occurred over the artic or pacific then few systems would be close enough to be effected, including sats.

 

[Morbius]

True but if the MIRVs were deployed early they would have spread out enough to require multiple interceptors, nuke or not.

sparke_pony,

You are limited by how far you can spread out your MIRVs; since you want to hit the target. For example, Russian warheads will probably be targeted at US ICBM sites in North Dakota, Montana, and Wyoming. That means there's a pretty narrow angle in which to disperse MIRVs.

The concern about radioactivity is kind of a "red herring". At the time one would use this system, one would have Russian warheads inbound. So one has a choice; take out the incoming warheads with your own small warheads with the detonation at high altitude; or you can do nothing and suffer the detonation of a large Russian warhead near the surface. There's no avoiding the radioactivity if someone has launched nuclear missiles.

As far as not being able to test; the aerodynamic tests of being able to intercept an incoming missile can be done with dummy warheads. As far as the nuclear testing of the interceptor warhead, that can be done underground, and was. For example, the Cannikin test which was conducted underground on Amchitka Island, Alaska was a test of the warhead for the Spartan interceptor missile. Here's a video about the test:



Basically, the reason the programs were not pursued is that the USA and the Soviet Union decided not to pursue them and entered into the 1972 ABM - Anti-Ballistic Missile Treaty where both sides agreed to limit missile defenses.

Greg

 

[SteamKing]

True but if the MIRVs were deployed early they would have spread out enough to require multiple interceptors, nuke or not.

For EMP I don't doubt the problem, just the range. If the intercept occurred over the artic or pacific then few systems would be close enough to be effected, including sats.

The EMP extends to the visual horizon from the initial burst point. If a single warhead were detonated at the proper altitude over Kansas, the effects of EMP would extend over the entire continental US. See the article in Post #17 for how the strength of the pulse drops off with distance from the blast.

 

[Morbius]

True but if the MIRVs were deployed early they would have spread out enough to require multiple interceptors, nuke or not.

For EMP I don't doubt the problem, just the range. If the intercept occurred over the artic or pacific then few systems would be close enough to be effected, including sats.

sparkle_pony,

Assume a position at which you are going to release your MIRVs and have them start to spread out.

Now calculate the maximum angle that you can have them spread out, and still hit Wyoming, Montana, and North Dakota which is where our missiles are.

Yes - you can spread your MIRVs out in a wide angle so they are difficult to hit; but then those MIRVs aren't close enough together to hit Wyoming, Montana, and North Dakota.

The angle to hit the US missile fields in the above States from Russia is fairly narrow.

Depending on where your interceptors hit; they are in a fairly narrow cone.

Greg

 

[sparkle_pony]

Depending on where your interceptors hit; they are in a fairly narrow cone.

But even a narrow cone is enough spread. Our intuition tells us that nuclear weapons can destroy anything within 10s of km. Games like "Missile Command" reinforce this perception. That is true for soft targets (read: cities) but not true for hardened targets like an RV. MIRVs spread over even ~5 km would be too disperse to negate with a single nuclear warhead tipped interceptor but still close enough to effectively attack a distributed target such as a missile field (note that silos are separated by large distances) or a metropolis (think LA).

But all this is irrelevant. Even if multiple RVs could be negated with a single nuclear tipped interceptor the enemy would just adapt their shot doctrine by spacing launches in time and from different launch points. That would ensure no RVs would be in roughly the same place at the same time. Hence it would be back to one interceptor for one warhead, and hit-to-kill kinetic interceptors would (economically) outperform nuclear interceptors.

RE: EMP I don't know enough about it to say one way or the other but just note that the trajectories of missiles in a northern hemisphere conflict will have most interceptions occurring over the Artic, far from Kansas.

 

[SteamKing]

But even a narrow cone is enough spread. Our intuition tells us that nuclear weapons can destroy anything within 10s of km. Games like "Missile Command" reinforce this perception. That is true for soft targets (read: cities) but not true for hardened targets like an RV. MIRVs spread over even ~5 km would be too disperse to negate with a single nuclear warhead tipped interceptor but still close enough to effectively attack a distributed target such as a missile field (note that silos are separated by large distances) or a metropolis (think LA).

You are assuming that the RVs can fly thru a nuclear blast and not suffer any ill-effects, either to the components inside the RV or to the ballistic trajectory the RV is on once it leaves the missile bus.

RE: EMP I don't know enough about it to say one way or the other but just note that the trajectories of missiles in a northern hemisphere conflict will have most interceptions occurring over the Artic, far from Kansas.

Again, you are assuming that the interception over the Arctic has worked flawlessly. But what if it doesn't? What if it takes multiple shots to take out an incoming warhead, shots that can't be made over the Arctic?

Further, not all nuclear strikes have to come over the Arctic. Russia has ballistic missile subs like the US, which are stationed off the Atlantic and Pacific coasts. If you want to cause some EMP chaos, detonate a nuke over the eastern seaboard. The EMP would wipe out a lot of financial and government records stored on unhardened computers, not to mention putting millions of people in the dark due to damaged electrical grids. It would make the aftermath of hurricane Sandy seem pleasant.

 

[Morbius]

You are assuming that the RVs can fly thru a nuclear blast and not suffer any ill-effects, either to the components inside the RV or to the ballistic trajectory the RV is on once it leaves the missile bus.
Again, you are assuming that the interception over the Arctic has worked flawlessly. But what if it doesn't? What if it takes multiple shots to take out an incoming warhead, shots that can't be made over the Arctic?

Further, not all nuclear strikes have to come over the Arctic. Russia has ballistic missile subs like the US, which are stationed off the Atlantic and Pacific coasts. If you want to cause some EMP chaos, detonate a nuke over the eastern seaboard. The EMP would wipe out a lot of financial and government records stored on unhardened computers, not to mention putting millions of people in the dark due to damaged electrical grids. It would make the aftermath of hurricane Sandy seem pleasant.

SteamKing,

I'm making NO such assumptions about flying through nuclear blasts. I'm just pointing out that the missiles have to stay within a cone, and the base of that cone is one of our US Air Force bases that has ICBM missiles. The size of the the Air Force base relative to the distance to the Russian missile fields is small in comparison; and hence the cone angle is pretty narrow.

I'm also well aware that not all launches will come over the pole and that Russia has missile subs. However, the Russians have a larger fraction of their missiles as land-based than we do.

Nuclear-tipped missiles weren't a "one-size fits all defense" that was supposed to handle everything.

You also have to separate the missile defense from whether you get into a war or not.

The purpose of developing these interceptors was that *given* a Russian attack, and *given* that a large fraction, although not all; of the attack would be missiles coming over the pole; is there anything you can do to blunt the attack, or are you just going to have to absorb the full force of the attack. The answer is that one can certainly blunt the attack with nuclear-tipped missiles.

However, both the USA and the then Soviet Union decided not to pursue this line of defense and save some money; and that is a purely political decision.

Whether one gets into a nuclear war or not is a totally different question and the probability of a war is not increased by having a partial defense.

Greg

 

[SteamKing]

@Morbius: I was responding to sparkle_pony rather than to your posts. He wants to minimize the effect EMP would have on US electrical and electronic infrastructure, which I don't think can be easily ignored, given recent history with recovering from natural disasters like Katrina and Sandy, not to mention cascading power blackout incidents on the US East Coast in 2003.

I agree that the whole idea behind nuclear-tipped interceptors was not well thought out, and even if it had survived into the 1970s or 1980s, absent the ABM treaty, it would have required that hardening of key assets against EMP be made lest these assets would be damaged or destroyed if an interceptor were used.

 

[Morbius]

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%20nuclear%20posture%20review%20report.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

 

[etudiant]

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.

 

[Morbius]

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

 

[etudiant]

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.

 

[Morbius]

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

 

[etudiant]

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.

 

[Morbius]

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 canceled purely on political grounds; it was canceled 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

 

[nikkkom]

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.

 

[Morbius]

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

 

[nikkkom]

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.