Casting doubt on Indian nuclear weapon designs and yields -2

G Subramaniam
BRFite
Posts: 405
Joined: 26 Apr 2006 17:58

Post by G Subramaniam »

I read an article by Bharat Karnad / Brahma Chellaney a few years ago,
that the Quantity goal for Indian nukes was
= Pakistani nukes + chinese nukes / 3
ShauryaT
BRF Oldie
Posts: 5350
Joined: 31 Oct 2005 06:06

Post by ShauryaT »

ramana wrote:What should India's posture be vis a vis PRC?
This begs the question, how is PRC is or rather should be perceived by India. The range is from enemy to adversary/opponent to competitor to neighbor to friend.

The views of strategic policy makers and political parties literally span this entire spectrum. Depending on who is in power or empowered will provide a drastically different answer.
PRC has its own challengers and has thus more demands on its inventory.

So quantitative parity is not required.
That is one view. Another view is in quantitative terms, India should be able to match the combined strength of TSP and PRC put together, assuming about a 40% loss, after a first strike and even then have enough to match anything thrown at it.
What about qualitative parity?
This should be a non negotiable concept. India has to catch up here, fast.
The 45 tests PRC has conducted are for weapons which are from kt to mt. Yes they are conducted in an era of unreliable and inaccurate delivery systems. So some sort of a reductuion is acceptable. But how much?
Enough tests to positively collect the required data to do sub critical tests and the ability to design new TN weapons in an Lif type facility. Also, at least a few full yield test, of deployable configurations. At least one MT level test and at least one test of each type of possible configuration not envisaged for current deployment. e.g: Neutron.
What is the minimum yield that would deter PRC?
There is no direct short answer. There are way too many scenarios and each scenario has a slightly different answer, depending upon what is at stake, the geo-political situation and the leadership in power. If you have to assume the bare minimum, then a simple KT device is enough in small numbers, but that is pre-supposing and simplifying down to a few scenarios only.
And how to achieve that? In other words how many without renewed testing and keep in mind fissile stockpiles are modest. And if the minimum cant be delivered then go back to drawing board.

Keep in mind that the FMCO campaign is ready to roll whoever is the next US President.
One way to achieve it is what KS proposes. i.e: All things being equal retain a minimum deterrent of about 100 and a fissile stock pile of 200-400. Cooperate with the west. Focus on building our economic strength. Quietly keep on working on delivery systems and ABM's. So, no more testing needed.

However, that assumes, certain scenarios. The thinking being the world and China will not be insane to start a nuclear war. BK on the other hand feels that, India needs about 400 weapons. Other Indian analysts fall in between but most under 150. Under BK’s scenarios, need all the tests, described above.

The fact of the matter is India’s CMD with NFU, allows all of these views to exist. This is a matter of concern and points to a lack of clarity and consensus in the NSAB itself, at the time.

My personal view on the matter is, if our national aspirations are to be a global power then our ability to project power has to match any and all potential plausible and probable scenarios, which factor all the known/ knowns and known/unknowns. Our policy should to have enough fissile material in quantitative terms to match China. At least 50% of China’s warhead numbers + TSP’s and qualitatively, match US capabilities in both missile and nuclear capabilities. I believe these can be achieved, in a cost effective manner, without jeopardizing the Indian economy or global ¾ letter treaties.

To understand the above, one has to think beyond deterrence and understand that nuclear weapons’ role as deterrents are only one seldom needed dimension, the more commonly used aspect is the concept of international power, in which nuclear capabilities, play a part among others. Mark my words – future generations of Indians will call folks such as BK – doves.

ramana: This was purely to state my views as I know you are a guru on these matters and perspectives.

Now, folks can go ahead and call me a dreamer, extremist, H&D, blah, blah but….I will ask them to read up the perspectives of the thinking portion of Indian military and see, where does their perspective fall.
ShauryaT
BRF Oldie
Posts: 5350
Joined: 31 Oct 2005 06:06

Post by ShauryaT »

shiv wrote:You can figure out how the Chinese could use 0.5 kiloton nukes against Indian forces or on Air bases. Consider also how attractive these ideas would seem to every small country on earth that feels threatened by the biggies.
I have fantasized with the idea that, instead of a single 2 MT warhead in a single missile, a 100 miniaturized 20KT TN based warheads on a single missle, would wreck absolute havoc and probably beat any ABM system out there. Once we do this, 20 missiles on land and sea will be enough to deter anyone. But then, I guess engineering would come in the way - for now.
Arun_S
BRF Oldie
Posts: 2800
Joined: 14 Jun 2000 11:31
Location: KhyberDurra

Post by Arun_S »

disha wrote:
Arun_S wrote:I am sure they had high confidence on S1 too till the moment S1 was tested. But I believe in BARCs mastery of boosted weapon. The question is credible yield that puts fear in the mind of adversary.
That is a very loaded statement. Is it megatons or few hundered kilotons? Is it 300 kt and above or @100-150 kt? Do you doubt the capability of BARC to deliver 100-150 kt? [/u]
I did not mean any loading. I do believe in BARC's mastery to design robust Fusion boosted weapons. The primary of S1 was a demonstration.

There is however related but orthogonal concept of credibility, that is based on demonstration. 100-150kt credibility requires a proof shot IMHO.
Arun_S
BRF Oldie
Posts: 2800
Joined: 14 Jun 2000 11:31
Location: KhyberDurra

Post by Arun_S »

shiv wrote:Has nobody thought of this before? I believe the US may have done some sort of calculation like this and realized over the years that value "c" is constantly increasing.That is when it was decided that the P5 (who probably all had some such thought about deterrence) decided that proliferation was not going to be allowed to spread weapons to all sorts of uncontrollable states.

For the US "c" changed from the USSR to USSR and China, with later additions being Pakistan, Korea, India, Iraq, possibly Iran ad a few others coming up.

The validity of your math may be fine from one viewpoint, but could they be expressing thoughts that existing powers had decades ago and decided to move on and shift the goalposts?

I may be wrong here - but I have begun to suspect that the nuclear haves have upped the stakes in the game form what is commonly thought of as "MAD" (Mutually Assured Destruction) to a new degree of hegemony based on technology and we may have to go that route too.

Apart from building large reliable arsenals of city busters, the emphasis is now on stopping all others from testing so that they don't get those city busters, but using their tech superiority to design small and efficient weapons that can have tactical value in defeating the small time upstarts without causing massive global level fallout.

One of the reasons I have been talking about fizzles and subkiloton testing and subcritical testing is that fission has been notoriously ineffective and wasteful of fissile material - with the Hiroshima bomb having been only 1or 2 % efficient. Increasing efficiency has increased yield. The next logical technlogical step would be to increase efficiency and decrease yield to make small workable weapons that can take out upstart nuclear nations without resorting to city busting.

I was researching the battle of Asal Uttar in 1965 before uploading a video with the same name on YouTube and in retrospect I realize that if the Pakistanis had a couple of small and efficient theater nukes they would have been in Delhi in 1965. India would similarly have been able to wipe the slat clean of Pakis in many areas had we had the weapons and tech in 1965.

You can figure out how the Chinese could use 0.5 kiloton nukes against Indian forces or on Air bases. Consider also how attractive these ideas would seem to every small country on earth that feels threatened by the biggies.
You are on the dot Shiv.
Few years ago there was BRF discussion on Tactical Nuclear Weapons, and I was amongst the few who propounded on the utility, efficacy and tactics of using sub-kt weapons in war against Pakistan.

The 5th Generation weapons are the coming shape of clean pure fusion powered explosives of 10-200 Tonnes TNT explosive power. It would leave no more harmful residue in dense areas, then say cordite. And it is a green explosive because it tiny environment footprint will quickly decay into background radiation of the environment.

US is only a few years away from realizing it. But I seriously doubt US will declare it is working weapon, before the CTBT/ fuel fabrication route is sealed shut for the rest of the world.
Last edited by Arun_S on 30 May 2008 08:38, edited 1 time in total.
John Snow
BRFite
Posts: 1941
Joined: 03 Feb 2006 00:44

Post by John Snow »

Sigma Qy(India) = Sigma (Sigma Fyc * Qy(c))

Shiv ji et al

If c1 is coeffcient for USSR/Russia
c2 for PRC
c3 for TSP
c4 for India
c5 for Noko
c6 for Iran

from uncles perspective

then

as time goes on value of c1 goes down and c2 being for fellow gang of five (ie brother Panda of uncle) will also go down (because uncle will be yeilding ground more to PRC), so c3 c4 and c5 c6 will increase over a time.

SO from uncles perspective he has to realign his nuke portfolio but not absolute numbers. He infact will fine tune door to door delivery and precesion Sub Kt bums for future.

****

My earlier estimate was 750 bums for India (at any time)

of all kinds
ramana
Forum Moderator
Posts: 59773
Joined: 01 Jan 1970 05:30

Post by ramana »

Shiv and all, Low yield is for war fighting ie is after breakdown of deterrence. Having said that during the 80s the RATS sued to churn out thesis on low yield bums and there is extensive bibliography citing this. Chris Bellamy a British writer wrote a 1980s book called "Future of land warfare' and he quotes these theses. So those ping pong balls that George kaka was disparaging could be that.

Another aspect of deterrence is the stuff has to be usable. So low yield is more usable as there is limited fallout and takes care of the prevailing winds etc that TSP keeps crowing about why India wont use stuff on them.

So there is a place and roll for everything.

ShauryaT, I am no guru. Onlee a shishya. Thanks for the detailed response shows you have been thinking about it.

One would want PRC to become a friend as it would be costly to be India's enemy.


I wish you would expound on qualitative parity.
One way to achieve it is what KS proposes. i.e: All things being equal retain a minimum deterrent of about 100 and a fissile stock pile of 200-400. Cooperate with the west. Focus on building our economic strength. Quietly keep on working on delivery systems and ABM's. So, no more testing needed.
These dont compute.
Raja Ram
BRFite
Posts: 587
Joined: 30 Mar 1999 12:31
Location: Chennai

Post by Raja Ram »

shivji,

I do not know much about tech, but I was told that the "chotus" are the real way forward by some of the more credible and knowledgable authorities. Your post gives me some idea of what they are talking about or alluding to.

If i recall correctly, right after the blasts enquoob also mentioned that more than the city buster TNs it will be the era of tactical nukes. Nowadays, enquoob does not participate in such threads I guess. He may share some insights on this i guess.
prashanth
BRFite
Posts: 537
Joined: 04 Sep 2007 16:50
Location: Barad- dyr

Post by prashanth »

self deleted
Last edited by prashanth on 31 May 2008 10:17, edited 1 time in total.
shiv
BRF Oldie
Posts: 34982
Joined: 01 Jan 1970 05:30
Location: Pindliyon ka Gooda

Post by shiv »

Raja Ram wrote: I do not know much about tech, but I was told that the "chotus" are the real way forward by some of the more credible and knowledgable authorities. Your post gives me some idea of what they are talking about or alluding to.

If i recall correctly, right after the blasts enquoob also mentioned that more than the city buster TNs it will be the era of tactical nukes. Nowadays, enquoob does not participate in such threads I guess. He may share some insights on this i guess.
Rajaram I don't know much about tech either.

But I do know that Plutonium gives off neutrons and decays by itself. A critical mass of Plutonium could explode because the neutrons it emits smash nearby atoms of Pu which give off neutrons and these split more atoms until the mass goes boom.

If you take a mass of Plutonium that is less than critical mass it will not normally explode. But if you can compress it effectively it could reach densities at which a chain reaction occurs, it can explode. Plutonium (Pu) fissions so fast that the mass of Pu itself gets broken up and disrupted before all the Pu can undergo fission. So it appears to be relatively easier to get a mass of Pu to explode (Atim Bum) partially. A good trick would be to get 100 percent of it to fission. I believe this is not technologically possible now.

This is obviously an area of research because it opens op so many possibilities. If you could get a marble size lump of Pu to fission and explode (may not be possible at all - I don't know)- it could perhaps be used to fuse a grapefruit size mass of Deuterium, so its a good research proejct.

If you take a biggish mass of Pu and fission it - you may get a yield of several kilotons, and that is frowned upon nowadays. But what if you take tiny lumps of Pu and compress them in some way. Maybe by laser or maybe by a bomb. You could figure out what the Pu is doing. I suspect these are "no brainer" experiments that have all been done. But all this will be "subcritical testing" that gives you data that you can use to design small bombs.

It is a difficult world Rajaram. In this world you are allowed to say that Indian nukes may not go off as expected in war. But you are not allowed to say that Chinese nukes may similarly not go off as expected. I am an ignorant person in these matters - but I believe that even in large inventories such as the Chinese inventory they do not have warheads that are guaranteed 1 megaton. Just like you can buy guaranteed 1 Kg potatoes in the market. I suspect that most warheads labeled "1 Megaton" (if they are labeled at all) are reasonably likely to work as stated and reasonably likely to give yield between 500 kilotons to 1.2 megatons or some such figure. The figure is unlikely to be precise and guaranteed. Heck there is no really good method of estimating yield even if you are sitting on a bum and feel it in your bum.

But then again. What do I know?
Last edited by shiv on 30 May 2008 21:30, edited 1 time in total.
John Snow
BRFite
Posts: 1941
Joined: 03 Feb 2006 00:44

Post by John Snow »

Chotus make it posssible to wage a nuke war and win it too. (at least the notion)

Chotus make it less likely to be abhorent to the moral (if any) protests of using a nuke.

Chotus when they fail will have minimal radiation effects unlike a mega bum if they fail can be a mega pain with contamination
satyarthi
BRFite
Posts: 179
Joined: 21 Aug 2006 08:50

Post by satyarthi »

shiv wrote: If you could get a marble size lump of Pu to fission and explode (may not be possible at all - I don't know)- it could perhaps be used to fuse a grapefruit size mass of Deuterium, so its a good research proejct.
If the grapefruit surrounds the marble, then the exploding marble will just rip apart the grapefruit without causing any fusion. For fusion to work very high temperature and pressures need to be created. Something has to be compressing the grapefruit from outside when the marble is exploding.

Chemical explosives that work with fission bombs are not adequate to compress the grapefruit to fusion. If so, we would not have needed the primaries in TN weapons. So, somehow you need to use the power from the exploding marble itself to compress the grapefruit. And we are back to the Teller-Ulam design of the staged TN. Teller-Ulam design can be miniaturized. There is nothing there which says that you have to have a large yield. You can have smaller yields.

On the other hand if inside the Pu marble, you put a tiny bit of tritium, then you can get a miniaturized fusion boosted fission.
satyarthi
BRFite
Posts: 179
Joined: 21 Aug 2006 08:50

Post by satyarthi »

Chotus are usable in the battle field. But Bade-Mians are still needed to deter debilitating attacks on our own cities etc.

Bade-mian to bade-mian, chote-mian subhan-allah.
Amber G.
BRF Oldie
Posts: 9263
Joined: 17 Dec 2002 12:31
Location: Ohio, USA

Post by Amber G. »

Few random comments: (FWIW / In My HO/ JMT etc…)

While I find posts from Shiv , Ramana and others very informative, some other posts here are what Richard Feynman once described as problem of “Length of Nose of Chinese Emperorâ€
Last edited by Amber G. on 30 May 2008 22:02, edited 1 time in total.
shiv
BRF Oldie
Posts: 34982
Joined: 01 Jan 1970 05:30
Location: Pindliyon ka Gooda

Post by shiv »

Satyarthi I am not talking actual design here.

There is currently a particular lower limit of mass for fission to occur. I believe that the greater the ratio of surface area to mass the more difficult the fission because neutrons escape away.

But open source seems to put 0.2 kilotons (or maybe 0.1) as the lower limit of yield. I have no information on the efficiency of that i.e how much Pu is wasted in getting such a low yield. Obviously - if you have a bad fizzle - you could end up getting 0.2kt from maybe 15 Kg Pu. That would be a waste.

But it looks like a problem that technology might be able to address. Just my guess.
ramana
Forum Moderator
Posts: 59773
Joined: 01 Jan 1970 05:30

Post by ramana »

Arun's problem is he doesn want to punch. He might still do it as he was told by some others too!
shiv
BRF Oldie
Posts: 34982
Joined: 01 Jan 1970 05:30
Location: Pindliyon ka Gooda

Post by shiv »

Can anyone educate me on what is a "Neutron gun" that is apparently used in fusion bombs to inject a flood of Neutrons when needed? I mean it's not exactly made in OFB is it?

Also does anyone know about the usability of elements like Hafnium and Californium in fission? Would you get these at Wal-Mart for example?
Gerard
Forum Moderator
Posts: 8012
Joined: 15 Nov 1999 12:31

Post by Gerard »

http://www.milnet.com/nukeweap/Nfaq4-1.html
These devices (sometimes called "neutron generators") rely on a miniature linear particle accelerator called a "pulse neutron tube" which collides deuterium and tritium nuclei together to generate high energy neutrons through a fusion reaction. The tube is an evacuated tube a few centimeters long with an ion source at one end, and an ion target at the other. The target contains one of the hydrogen isotopes adsorbed on its surface as a metal hydride (which isotope it is varies with the design).

When a current surge is applied to the ion source, an electrical arc creates a dense plasma of hydrogen isotope ions. This cloud of ions is then extracted from the source, and accelerated to an energy of 100-170 KeV by the potential gradient created by a high voltage acceleration electrode. Slamming into the target, a certain percentage of them fuse to release a burst of 14.1 MeV neutrons. These neutrons do not form a beam, they are emitted isotropically.
Gerard
Forum Moderator
Posts: 8012
Joined: 15 Nov 1999 12:31

Post by Gerard »

Little-studied metal goes critical - Neptunium Nukes?
The new measurement of neptunium-237, the artificial metal's most common and stable isotope, shows that it "is about as good a bomb material as U-235," comments Richard L. Garwin of IBM's Thomas J. Watson Research Center in Yorktown Heights, N.Y.
ramana
Forum Moderator
Posts: 59773
Joined: 01 Jan 1970 05:30

Post by ramana »

PKI had written articles about these. And NPA mullah from Princeton (von something) had pooh-poohed him. However in some other context it was revealed that uncle had tested such non traditional fissile materials. However you need a fancy reactor system to grow them.
vsunder
BRFite
Posts: 1353
Joined: 06 Sep 1999 11:31
Location: Ulan Bator, Mongolia

Post by vsunder »

I shall try to explain Rayleigh-Taylor instability. Here is the classical experiment. Take a test-tube of water. Now carefully pour Mercury on top of the water and examine the interface between the Mercury and water. Is it a straight line? Answer NO. Fingers of Mercury enter into the water.
Now pretend the water is matter and Mercury is radiation. Then if the radiation penetrates the matter non-uniformly as above presumably the
matter does not get compressed uniformly. Such instabilities have to be guarded against in the compression process.

If you need to understand this from a completely layman's perspectives Read Kip Thorne a very famous astrophysicist at Caltech book, called Time warps, something something... In fact Kip Thorne has a nice picture
of this phenomena in a gigantic scale The Crab Nebula. There are fingers.

If you really want a very deep understanding of RT then friends you will have to plough through Chandrasekhar's book "Hydrodynamic and Hydromagnetic Stability" This is a very detailed analysis of this classical phenomena. Chandra does it very rigorously and thoroughly as only he can!!!!
ramdas
BRFite
Posts: 585
Joined: 21 Mar 2006 02:18

Post by ramdas »

Arun_ji

It looks like the two sub-kt tests on May 13 of 0.5 kt and 0.3 kt were not detected by outsiders. Would it not be possible for any nuclear power to conduct sub-kt tests in a large underground cavity (of say , 50 m diameter) undetected ?

Can tests at these yields with a neutron bomb yield a good understanding of the secondary in general ? In that case, they can be used to fix S-1 if at all S-1 did not work as expected.

In this case, even if there is a suspicion of something going on, the powers that be will be silent so as to keep their make believe world intact. Unfortunately, our govt is not likely to look at this option.
Amber G.
BRF Oldie
Posts: 9263
Joined: 17 Dec 2002 12:31
Location: Ohio, USA

Post by Amber G. »

There is however related but orthogonal concept of credibility, that is based on demonstration.
Got a chuckle, though did not understand, the exact reference here. Old joke is one can judge how sophisticated a mathematician is by seeing what she uses - "Ninety Degree"(middle school) , or "right angle" (High school) or "perpendicular" or "normal" or "orthogonal" , or "orthonormal" (grad school) etc..)
Anujan
Forum Moderator
Posts: 7806
Joined: 27 May 2007 03:55

Post by Anujan »

Amber G. wrote:Got a chuckle, though did not understand, the exact reference here. Old joke is one can judge how sophisticated a mathematician is by seeing what she uses - "Ninety Degree"(middle school) , or "right angle" (High school) or "perpendicular" or "normal" or "orthogonal" , or "orthonormal" (grad school) etc..)
Sorry to nitpick, but "ninety degree" and "perpendicular" are concepts from geometry but, "orthogonal" is a generalization and a concept from algebra. One argument may be orthogonal to the other (having no bearing on the other) but considering one argument to be perpendicular to the other is a bit weird, arguments are not lines :)

About Rayleigh-Taylor and Richtmyer-Meshkov instabilities. Basically a fusion weapon works as follows. The fission primary goes off and emits xrays which is absorbed by the bomb casing. These xrays are then re-radiated by the casing on to the fusion fuel container. The outside walls of the container absobs this radiation and essentially boils off. Since the outer layer is flash vaporized, the inner layers collapse inwards (newton's law), compressing and heating the fusion fuel inside. (The Xrays also compress and heat the fusion fuel due to radiation pressure. open source literature differs on how much ablative pressure vs how much radiation pressure).

Now comes the problem. two things may happen, (a) various instabilities. Since the gas is being compressed from the outside, a shockwave or a high pressure front passes through the gas. If it passes through uniformly, the fusion fuel gets heated and compressed uniformly. But the problem is as follows: A high pressure front slamming on a gas is like a dense liquid slamming on a not so dense liquid. Instead of the surface pressing down uniformly, "finger-like" projections start appearing (think of it as you pressing a foam pillow with your hand, it doesnt get pressed uniformly, your fingers sink in) which then creates turbulence and interact and weaken the shockwave. (a) spalling of the walls of the fusion fuel container - that is small pieces break off and go "zing" inside the container leading to more turbulence. Note that any references to spalling in open source literature may be a deception. "Spalling" may be a code word to describe non-uniformities in the radiation heating of fusion fuel due to slight variations in the thickness of the walls of the fusion fuel container (so the xrays dont penetrate uniformly).

You might wonder, doesnt the fission bomb going off destroy the whole bomb assembly ? The fascinating thing is that light (xrays) are much much faster than sound (shockwaves) and reach, compress and heat up the fusion fuel long before the shockwave from the primary destroys the entire setup.
Last edited by Anujan on 31 May 2008 01:54, edited 1 time in total.
ramana
Forum Moderator
Posts: 59773
Joined: 01 Jan 1970 05:30

Post by ramana »

Dont tell me your into this business and have Phd too. I guess RC is getting his peer review whether he liked it or not.

I am worried what the next question will be and know what the answer is.


:(
John Snow
BRFite
Posts: 1941
Joined: 03 Feb 2006 00:44

Post by John Snow »

One argument may be orthogonal to the other (having no bearing on the other) but considering one argument to be perpendicular to the other is a bit weird, arguments are not lines
Very well said lakshmic!

going orthogonal arguments are not lines but have range and domain!
svinayak
BRF Oldie
Posts: 14223
Joined: 09 Feb 1999 12:31

Post by svinayak »

These are the real piece of info we are getting in BR for the first time
Amber G.
BRF Oldie
Posts: 9263
Joined: 17 Dec 2002 12:31
Location: Ohio, USA

Post by Amber G. »

lakshmic - Thanks for taking time to post, it does make it very clear.
(Though I would argue, instead of using the term "basic nuclear physics" "basic fluid dynamics" may be more apt)(BTW - have seen people using 'orthogonal' when normal or perpendicular could be used to - ... ok okay I am not going to go on any tangent here ...:)
Anant
BRFite
Posts: 321
Joined: 02 May 1999 11:31
Location: Iowa City, Iowa
Contact:

Excellent posts

Post by Anant »

Hello all,

I just want to say excellent posts. As a scientist in an unrelated discipline, this stuff is just fascinating to me. Lakshmic, your post spoke to me after I re-read the article from the Progressive magazine. In that, they made a huge deal about the thickness and uniformity of the U-238 casing. Based on your clear explanation, to a layperson like me, it now makes sense why these tolerances are so critical, vis a vie unequal compression of the fusion source via X-rays and the two phenomena that you detailed. Shiv, thank you for starting this thread. Rest, please keep posting. Learning a lot.

Anant
ramana
Forum Moderator
Posts: 59773
Joined: 01 Jan 1970 05:30

Post by ramana »

So its that CNC stuff that SUnil used to talk about after all!
Arun_S
BRF Oldie
Posts: 2800
Joined: 14 Jun 2000 11:31
Location: KhyberDurra

Post by Arun_S »

ramana wrote:So its that CNC stuff that SUnil used to talk about after all!
And Alok_N used to rip that CNC argument. How ironic that their minds and thoughts are now fused into one, lording con-fusion in fools paradise.
Anujan
Forum Moderator
Posts: 7806
Joined: 27 May 2007 03:55

Post by Anujan »

ramana wrote:Dont tell me your into this business and have Phd too.

So its that CNC stuff that SUnil used to talk about after all!
Ramana-saar,

Phd and work in releated area. I am of course not a bum maker. R-T instability is well studied in supernovae, where the fusion blows the outer "shell" away and R-T instabilities cause "fingers" in the resulting nebula. The crab nebula is well studied in this regard.

I dont know what CNC stuff sunil used to talk about, but CNC is very useful in fusion boosted fission weapons as well. There, there is a plutonium ball, surrounded by explosive "lenses" (basically another ball of mix of fast exploding and slow exploding explosives).

Now remember shaped charges and explosively formed penetratrors (EFP - our jihadis in eye-raq are pretty good at it). It is a cylinder full of RDX and covered by a hemispherical cover (incase of EFP, cone incase of shaped charge) with the cover projecting "inside". Now the explosive is set off from the other end. When the explosive goes off, usually the shockwave diverges (and pieces get shattered and thrown in all directions), but because the shockwave reaches the center of the plate first, followed by the edges of the plate later (because the center of the plate is projecting "in" and nearer to the detonation point), the shockwave converges and the plate gets crumpled into a ball and thrown out at high speed. The shock wave acts just like your hand crumpling a piece of paper, the palm pushes the paper out and the fingers crumple them in. Theoretically if you crumple and release your fingers quickly, the paper should become a ball and go flying out of your hand. So the plate acts like a "lens" making the shockwave "converge". Ofcourse this can be made better by mixing explosive of differring denotation speeds and so on.

Now imagine an EFP facing this EFP, these two balls will slam on each other. For that matter imagine 4 EFPs at right angles to each other facing a common center, four balls will slam on each other. This is our FBF bum. Now the problem is that if the plates are not uniform and of there are gaps between the explosive "lenses", plutonium would simply "squirt out" of the gaps. This is again like squeezing a kneaded atta with your hand, the atta goes between your fingers and "squirts" out. Now if stuff is near, neutrons released due to fission cause more fission. So the more stuff squirts out, the less stuff to fission. In the worst case, it might be a dud. Why is a "gun type" okay for uranium but complicated lenses for plutonium ? This is because, plutonium is more fissile and as they come together, even before they touch, they start reacting. The heat of the reaction pushes them away and makes them a dud. So we need (a) several pieces so no two pieces touching causes a reaction (b) Bringing them together at high speed so they slam into each other even before they start going off.

So three things are needed. Machining the plutonium "pit" to uniform thickness (and density) all around. Packing identical quantities of explosives. Setting them off at the same time. Note that exploding-bridgewire detonator thingie is used to set off all lenses at the same time. Ordinary electric dentonators take too long to "heat up" and cause detonation. Some detonators may heat up quickly and set off the detonation first others may set off later. So the detonation may be milliseconds apart if they have imperfections and non-uniformities.

Here is a fascinating rumor (note the word rumor). Apparently the explosive lenses are are not placed equidistant from the center, but at differring distances (small difference, diffcult to see). So they have to be set off one by one in some sequence (instead of setting them off all at the same time) so the pieces slam into each other at the same time. The sequence in which they should be set off is the "code" to set off the bum. If the code is wrong the pieces dont assemble to form a sphere, instead they destroy each other and the bum is a dud. So apparently nucular codes physically prevent them from going off and there is no "short circuiting" them as shown in movies. Again, I dont know, this is just a rumor, but thinking about it makes sense.

Mastery over 3 things are needed, machining the pit perfectly so no different thickness density and so on and so forth. Packing the explosives properly (again by machines I presume), same quantity, perfect shape, density and so on and so forth. Making the EBW detonator (supposedly hard to get, this is called as the "high speed switch" that our pig neighbors were caught importing some time back). Now R-T and R-M instabilities dont play much of a role in fission weapons (according to opensource), because of slower compression, lower pressure and metallic pluotonium. (When compared to fast compression, high pressure and gas being compressed in fusion secondary).

In my next post about why I dont know about CNCs in fusion weapons.
shiv
BRF Oldie
Posts: 34982
Joined: 01 Jan 1970 05:30
Location: Pindliyon ka Gooda

Post by shiv »

Fascinating and well written stuff lakshmic. Dil maangta hai more.
Anujan
Forum Moderator
Posts: 7806
Joined: 27 May 2007 03:55

Post by Anujan »

ramana wrote: I am worried what the next question will be and know what the answer is.
:(
ramana-saar,

I dont know if S1 was a dud. Neither do I know where RC's confidence comes from. Here are a few things to consider

a. Fusion weapons are a myth. Usually the energy released by a TN weapon is somewhat like 2:4:1:6 (2 part from primary, 4 parts fusion, 1 part "spark plug"---a mini fission weapon in the center of the fusion fuel container and 6 parts from the irradiation of the U-238 casing and tamper. The ratio is of course representative and varies based on the designer's design.

Now, if the SDREs used an "inert" casing and tamper, thereby stopping with fission primary and fusion secondary, essentially the bum's yield can be doubled with the same setup, with simply a blanket of more U-238 around the casing and without touching the configuration or the amount of the fusion fuel. This seems plausible, because most of the dirty fallout is because of the U-238 and SDREs probably dispensed with it to contain the yield as well as the fallout.

Assuming perfect world (nobody is traitor, everybody is competent), RC's confidence about doubling or even tripling the yield may come from this fact. So essentially SDREs may be able to make 150KT TN weapons of almost identical designs.

b. I would be really surprised if S2 was a pure FBF weapon without "TN configuration". That is S2 is a FBF fission primary and a fusion secondary minus the gas and with instrumentation to study the radiation triggered implosion. Ofcourse, press reports of "warhead configuration" contradicts this.

c. On the other hand, S1,S2 may have been 25, 25 KT each with the fusion being a complete dud (not even a partial burn). Note that PoK-1 achieved 8KT minimum, was probably not a FBF design. Assuming 3 fold increase in efficiency, a similar weaponized design's yield would be around 24KT. So a total yield of 50-55 KT might just be the FBF weapons going off and the fusion being a complete dud. There is no way for others to know because of simultaneous detonation. Only the SDREs holding the "sethoscopes" on the bum, on site, would know.

What I am afraid though is that RC setting policy. Maybe it is RC's estimate that our FBF weapons will be enough deterrence for the next decade to a decade and a half, within which everyone will start to test again and we can jump into the fray and test our "fixed" TN weapons. If so, this is very very harmful thinking, RC's job is to give us a working bum, not to make strategic analysis.

In any case, there is no excuse for not testing more.
Last edited by Anujan on 31 May 2008 06:20, edited 1 time in total.
ramana
Forum Moderator
Posts: 59773
Joined: 01 Jan 1970 05:30

Post by ramana »

No in the press conf on May 16th, S2 was stated to be a palin vanilla fission from stocks. So no surprises there.

BTW, thanks for the three posts you have clarified for lay people how complicated thsi whole thing.

I like the ball of atta analogy. I use the balloon analogy. yours is more appropriate for the desi log.

So instead of a nice laddo you can get choor and its all kallash.
achy
BRFite -Trainee
Posts: 76
Joined: 26 Jan 2008 00:36

Post by achy »

lakshmic ,

Fascinating read.

Also, your post illuminates why bum making is complex fusion of physics and engineering. How can we now say that we dont need more testing. This also explains why P5 tested so many times and why their energy are focussed on restricting testing.
Anant
BRFite
Posts: 321
Joined: 02 May 1999 11:31
Location: Iowa City, Iowa
Contact:

CNC Primers

Post by Anant »

Hello folks,

Here is another good link from the Lawrence Livermore labs. It showcases the different CNC machines used for nuclear weapon design and "other purposes."

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

Here is another link.

http://www.fas.org/nuke/intro/nuke/produce.htm

What is fascinating is that every leap in nuclear weapon bum design coincided with concomitant increases in machining ability. So, atleast in this field, it appears that you need theory (the really smart people that post here) and practice (the boots on the ground who can operate machine tools to the highest tolerances).
Anant
BRFite
Posts: 321
Joined: 02 May 1999 11:31
Location: Iowa City, Iowa
Contact:

It's the "Pits"

Post by Anant »

Ok folks,

more cud to chew on. Here is a document from FAS, derived from the US government, on weapons design, weapons turnover (which I think is a huge issue with a larger arsenal), plutonium pit design and fabrication and metallurgic characteristics of plutonium. You'll find fascinating stuff from page 28 on. The rest is interesting also because it gives you a logistical snapshot of what is needed for bum production.

www.fas.org/sgp/crs/nuke/RL33256.pdf
ramana
Forum Moderator
Posts: 59773
Joined: 01 Jan 1970 05:30

Post by ramana »

So if this stuff is so complex and complicated then how will the using agencies assure themselves that newer weapons like rrw will work as the previous ones? So sure as daylight there will be a resumption of testing.
Anant
BRFite
Posts: 321
Joined: 02 May 1999 11:31
Location: Iowa City, Iowa
Contact:

Post by Anant »

Ramana,

I'd fully agree with your assessment. From reading that article (from the US perspective), some things are clear. There is only one plant that can make the plutonium pit for the W-88 warhead. In the American context, all pits for American bums have to be certified. The one for the W-88 is yet to be certified. Apparently, as the article states, the US is now the only country in the P-5 without a certified facility to make plutonium pits (now for its most complex W-88 warhead). Perhaps in the US context, testing can take a different nuance, aka no need to test the whole gadget, perhaps cold test. But as you said, if this stuff is so darn complex, then surely India has to test and must test I would think as a policy decision.
Locked