Pokhran II not fully successful: Scientist - Part-3

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samuel
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by samuel »

shiv,
it depends on what's between the lada and mikes.
having known its lada, you can try to figure out what medium does.
using that understanding of medium you can try to figure out that what you are hearing is now, not lada, but something much powerful.
depending on what you do and what the medium does, you can interpret that something else to be much louder
than it is or weaker. even if the medium does not change what it does changes depending on what it is responding to.

for people getting to be experts around 20 odd years ago, nonlinearity was a novelty that was eliminated by linearizing.
i.e. is y = x*x and you were only interested in the vicinity of x=1, you could potentially just use a linear approximation.
More recently, people have in many fields moving this assumption forward because
a) nature is not linear at all, but that is too broad a statement, we need to study the soil's properties.
b) anisotropy (which is linear) and nonlinearity play far interesting roles. so do geometric effects and wave effects.
The spectrum of one bomb is not the same as the nuke, and characteristics of detector (which can be better estimated) are also up for grabs.
c) new methods are needed to tackle these issues.

so. to answer your question, yeah if it wasn't a lada but mercedes, you could probably identify that. if it was a convoy of
jackhammers, not so sure. That's how engineers typically get screwed. Linearization. For good answers you need to know a lot of prior knowledge.

In fact, if you want to do this well, use techniques like time domain reflectometry or better yet frequency domain reflectometry on a wire (the signal there is always known)
and do it near the blast. Might have better luck. I don't know if they did that.
S
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by shiv »

Thx Samuel - point taken
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by shiv »

Even if India never tests another nuke, Santhanam's accusation that Pokhran II was a fizzle isn't as damning as it might sound. For nuclear scientists, fizzle is a technical term for detonations that yield 30 percent less concussive force than expected, and Santhanam himself acknowledges that India's thermonuclear device yielded an explosion equivalent to 15 to 20 kilotons of TNT — the rub is that it was intended to generate 45 kilotons. The minimum deterrent lobby argues that's powerful enough to dissuade Pakistan from getting any crazy ideas, and even if India's nukes pale in comparison with China's, they're still devastating enough to give any rational adversary pause.
But for others, the niggling fear remains that doubts about the capacity of India's nuclear bombs make it all the more likely that one day it may have to use them.
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by NRao »

c) new methods are needed to tackle these issues.
Nope.

That is why in a designed yield of 45 Kt they have +/- 10 Kt variance.

:mrgreen:

We have to be glad it is not +/- 35 Kt, I guess. That is based on BR_concern.

BUT, who cares. As long as a 150 Kt whatever can keep the rat out of my basement. That is all that matters. Of course at the lowest possible cost.
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by NRao »

shiv wrote:
Even if India never tests another nuke, Santhanam's accusation that Pokhran II was a fizzle isn't as damning as it might sound. For nuclear scientists, fizzle is a technical term for detonations that yield 30 percent less concussive force than expected, and Santhanam himself acknowledges that India's thermonuclear device yielded an explosion equivalent to 15 to 20 kilotons of TNT — the rub is that it was intended to generate 45 kilotons. The minimum deterrent lobby argues that's powerful enough to dissuade Pakistan from getting any crazy ideas, and even if India's nukes pale in comparison with China's, they're still devastating enough to give any rational adversary pause.
But for others, the niggling fear remains that doubts about the capacity of India's nuclear bombs make it all the more likely that one day it may have to use them.
I am glad someone outside India also made that statement.

I owe this guy a biryani I guess.
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by sohamn »

Guys we need to understand something --
during 1998 BJP govt took at daring step in going for a nuclear test. The govt gave the scientists only one chance. And govt. couldn't even have given any more chance. The international scenario wouldn't have even allowed another series of tests, if we had done another set of tests we would have been internationally isolated. So our scientists had only one chance.

Given only one chance and that to without any outside help it is quite probable that some tests wouldn't have been perfect. But the reality is that we can't rectify that now unless there is another provocation or we become a superpower. I think atleast our Fission tests were successful and we could have weapons of atleast 50kt design. This is quite a deterrence. And right now govt. can't risk another test and go through a financial crisis and embargoes.

Lets see how the future evolves and as Kalam has said we should be doing tests only in Supreme national interest.
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by enqyoob »

OK N3 - a question before SHQ gags you:

What if you are Lada P fan living in Norway and you have never had a chance of using mike A and B to get any correction function, and you get Mike A and start trying to pick up Lada P from Norway. How good is your recording going to be? (or should I say "How good is it going to B")
I don't think they have any hope except by "guessing" based on "the Siberian Steppe has this value and Thar Desert is just as cold as Siberian Steppe therefore" etc. etc. .... as they did. Without the calibration function to unscramble it, it looks completely hopeless. In the time domain, as samuel points out, what you see is that as amplitude goes up, and waves propagate through complex media, all sorts of things happen. The waveform gets extremely distorted. In a 2-D analogy (and in fact image processing is just a 2-D equivalent of the procedure I outlined b4) Jayalalithaaa may start looking like Arundhati. A wave that started out with a very sharp front may decay into a much more gradual wavefront. Or the reverse may happen and a gentle wave may become one with a sharp front. Reflections will mess up the waveform. So time-domain analysis flunks, as Samuel so knowledgeably explains.

And if Samuel says that he can't get the right answer, who am I to correct him? 8)

This is why I posted the rationale for the very simple frequency domain approach. In the frequency domain, this can be seen as a change in amplitude, distributed as a function of frequency. Different levels of absorption happen to different frequencies. Worse, the propagation speed depends on frequency, and different parts of the wave travel at different speed. So .. their arrival time at a given spot varies with frequency. This is why you need the Phase of the Transfer Function. Briefly, a delay of 1 millisecond for a 10Hz signal component is only (1E-3)/(0.1) part of the 360-degree cycle, or 0.036 degrees phase shift. But the same 1 millisecond delay for a 5000Hz component is a full 180 degrees. No problem. By carefully thinking through the Magnitude and Phase of the Transfer function Abdul can decode all that.

Now.. if the amplitude is so great that energy gets passed from one frequency TO another, things may get more difficult, but nothing that a good experimenter (or even I) could not fix, with my vast experience of cooking lab reports at the Eye Eye Tea. Besides, I don't think that beyond the immediate fracture region, the soil movement loads are great enough to do anything of the sort: as earthquakes go, this was very mild, and what happens to signals at much higher amplitudes is well known.

Even if the amplitude is very large, you can look, say, at the time domain signal and be slightly smarter, such as looking at the rate of growth of the signal, or the second derivative, fit that against theory, and therefore get a good estimate of the precise amplitude.

As one might imagine, what works for the expensive microphone with gentle rock concerts may not exactly work with say, a shock wave in a supersonic flow. But that has not prevented "engineers" from being able to capture shock structure to great detail inside supersonic jets or over hypersonic projectiles, so there is no reason why the same techniques cannot be extended to the Really Loud Lada P concert. The knowledge base is very well established for shock structure, propagation and wavefront distortion.

As the Official Statement of Sep. 15 said:
We have some of the world's best authorities on .... soil mechanics, ... etc


That does not mean that they can just dig holes or test soil in a test tube. I think they understand quite well the nature of shock propagation through solid or multiphase media. If you Google terms like "shock propagation solid" for instance, I bet you see a lot of Abduls and Lakshmikuttys besides Georges and Pierres.

But.. any way, whatever the means, once you have done the calibration, you have bypassed a massive simulation problem. IF and only IF you have the calibration function to do the correction. You keep that locked up in a safe.

Simulations without actual on-site data are hopeless, IMO. Even if the Norway-based Experts are the greatest in Soil Mechanics, etc. etc. etc., all I have to do is drill a whole range of holes (tubewells will do fine, but pretty closely spaced) in a very crude circle around the S1+S2 sites, pour cement down half of them and water down the rest or put in some railroad shock absorber/springs /Pokhran garbage / wood pieces down the rest ... and you've messed up all their simulations. Just an example - I have no idea if they did anything like that.

There is one exception that the Norwegians will claim. Really large explosions apparently send enough energy down into the molten mantle of the Earth that waves propagate through that, clear around the globe. It's largely homogeneous molten stuff down there (looks golden in my madarssa Geology 4 Abdul picture book), and they have plenty of correlations between signals going through that due to huge earthquakes. For instance, Krakatoa going off and the thing that caused the 2004 tsunami, were read like that, I believe.

But I read somewhere that the POK-2 waves were measured only through the near-surface crust, not through the molten mantle. The crust is some 10 kilometers down, which is a very long way for something that can't even bust through 200 meters. So again, the Norwegians are screwed unless they have the real calibration function. You see why they tend to beat up even Khetolai kids found inside the perimeter. If someone installs a good charge of RDX somewhere down a well in that vicinity and stands outside with sensors and a laptop computer - or even a recorder, they may start getting very close.

The one statement that sends real chills down my tail is the one by the See Ai Ayy that claimed total ignorance of what goes on inside the desi nuke establishment because it was impossible to penetrate. With your vast experience of reading spy novels, think about why anyone would make a statement like that in public, and I really lose hope.

I don't want to start another spate of :(( to Webmaster, so I will leave it at that.
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by Sanku »

amit wrote:
Sanku,

I don't buy your two competing approaches theory. Intially I did but after the antics of this so-called BK camp I've changed my mind competely.
Indeed Amit, you dont have to buy anything since I am not selling anything either, as I said before selling things is a job that others do not me.
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by Sanku »

samuel wrote: for people getting to be experts around 20 odd years ago, nonlinearity was a novelty that was eliminated by linearizing.
I love you Samuel (purely from a technical standpoint of course)
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by Gagan »

What's with that cut off date for ALL nuclear explosions by the end of 2010?
This is part of Ombaba's UN piss plan.
Any opening there for India?
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by enqyoob »

Now that he has won the NPP, why should OB waste political capital pushing NPT and CTBT and FMCT and IFCCC? He can become a popular President by resuming nuclear testing with hypersonic missiles into the center of the Antarctic Ice Cap. And by helping Israel enforce the NPT in Quom.
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by samuel »

Thanks Sanku. I wanted to write something similar one or two times myself, but thought it might come across as a bit odd. But yours came across fine, so "to you too" with thanks.
S
PS: But I really want to know what happened there. Did anyone find any other "crackamides" in equally distant or nearly equally distant settlements. There seem couple along NH15.
Because this is all part time, it will take a little time, but pretty pix will follow.
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by Sanku »

Quite likely that Ombaba was sure that he will have a good reason before the announcement was to be made, although the prize was already decided within 10 days on the basis of who does what.

Its KSs fault onlee.
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by Sanku »

samuel wrote: PS: But I really want to know what happened there. Did anyone find any other "crackamides" in equally distant or nearly equally distant settlements. There seem couple along NH15.
Because this is all part time, it will take a little time, but pretty pix will follow.
As I said, I have been to Pokharan personally within Six months. And no nothing else cracked (including similar structures by the Army within 5 km radius) other than Pokharan village walls (a few)

Even on Pokharan ones we are not certain when they cracked.
Last edited by Sanku on 09 Oct 2009 23:22, edited 1 time in total.
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by samuel »

How can we help Ombaba tack right to us?
S
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by samuel »

Sanku wrote:
samuel wrote: PS: But I really want to know what happened there. Did anyone find any other "crackamides" in equally distant or nearly equally distant settlements. There seem couple along NH15.
Because this is all part time, it will take a little time, but pretty pix will follow.
As I said, I have been to Pokharan personally within Six months. And no nothing else cracked other than Pokharan village walls (a few) (including similar structures by the Army within 5 km radius)

Even on Pokharan ones we are not certain when they cracked.
Oh, that's great news, sorry, I should've been reading this from start. OK, that is very useful to factor in.
Thanks
S
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by SaiK »

also take account of those cracks made just to get compensations. :wink: .
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by Kanson »

shiv wrote:What if you are Lada P fan living in Norway and you have never had a chance of using mike A and B to get any correction function, and you get Mike A and start trying to pick up Lada P from Norway. How good is your recording going to be? (or should I say "How good is it going to B")
If put that to context, i feel, the scenario described is not apt. Some thoughts towards that:

1. Seismic events are happening throught out the year every day albeit at low intensity. Earthquake or explosion is represented as Seismic activity. Even as the explosion is new to that place, earthquake may not be
2. There are clusters of Stations that record every Seismic activity. Not two or three. And they are scatered more or less throught out the azimuthal plane.
It gives numerous data points to cross check and for correction.
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by SaiK »

well the earthquake of mag 6.5 at afghanistan had a focal depth of 18 km. The energy release is equivalent to a 2000 kiloton nuclear explosion. (UC Berkeley).
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by Amber G. »

I have a query for those who know about transmission of signals of any kind. I mean any - We may be talking of sound in the air, sound in water, seismic signals, electricity, light, other electromagnetic signals - whatever.

If a signal of any energy is generated at a point and is measured at great distances arriving through varying paths of unknown or variable conductivity it is obvious that the signal gets degraded and weakened over distance.

On receiving such a signal, what methods are used for guessing or estimating the original signal strength?

If you were tasked with estimating the original strength of any signal from a point source very far away, and assume you had means to set up any apparatus anywhere as long as it is at a great distance (500 km or more) from the source, what would you do to arrive at a best possible estimate of the magnitude of signal?
Shivji - FWIW

Some times one is lucky and get a pretty good estimate of original signal strength -- For example Electon jumping an energy level and producing a 1.9 ev photon which escaped from sun (or vega for that matter) will still have the same energy and if I see it through a spectrometer (giving me a H-alpha line etc) and I can estimate/guess the energy released in that event.

So it certainly depends on what kind of equipment I have and how the strength of signal is decaying (even more important - how the s/n ratio is increasing with distance).

Let me give another example - Suppose I want to find KE of thermal motion of a water pool (IOW its temperature) and the pool is far away. Accuracy of my infrared camera may be not very high if the pool is far away but suppose I see that there is floating ice in that pool (which is caught by camera)...and the water happens to be in equilibrium with ice ... I can pretty well guess the temperature is 0 deg. C and calculate the KE.


Some times additional information can help.

But the same camera may not be able to detect if a person has a fever or not from the same distance.

A simple photo of a fireball - One can estimate the yield with one precession...
If I can get a pretty good spectrum of the fireball I can estimate the yield with much more precession...
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by SaiK »

btw, testing in atmosphere should not attract seismic detectors right?
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by Amber G. »

On a lighter node - saw some where -
There is a lot of sizzle/fizzle debate about current Nobel Winner
I don't mean Obama but Venkatraman Ramakrishnan who was was born in Chidambaram, TN
Should we start the whole fizzle/sizzle debate again?
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by samuel »

We should have a thread on "general systems theory" "statistical mechanics" "multiphase, multiscale and multirate phenomena" and "strange attractors" Our transformation from the munchies of pokhran to the mensch of science will be complete and we can then sell ourselves as a "virtual university" better than wikiversity to some publishing house or institute for millions of bucks.

S
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by NRao »

Start with "game theory". IF we can come to a decent resolution, then the rest may have (some) value. ?????
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by samuel »

there is no resolution to MAD. like renormalization it keeps reintroducing the worthlessness of our last piece of arsenal--the entire advantage lies in the differential and in balance lies deterrence. but supposedly it does reach nash equilibrium but because no rational person would find this strategy remotely rational, it is not pareto optimal -- everybody is worse off. So, let's start a Department of Long March to the End of International Nuclear Weapons (LoMEIN Department)
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by shiv »

Thank you all for your informative inputs.

It appears that in the absence of some fortuitous circumstances, most signals undergo degradation that make them weaker and less characteristic of the original over distance and under such circumstances the conclusions about the original signal can be erroneous in the absence of prior error correction systems such as those patented by fans of Lada P. concerts. Would I be correct in saying that the chances of error become higher if the signal is just a unique one off signal of very short duration rather than an entire concert? Like a single fart in a Deep Purple performance?

But let me add more conditions to the question

The problem I am asking about is the ability to assign value of strength to the source of that signal which should (ideally) match the original signal value with an acceptable error (maybe 10 %?). General reading suggests that the actually error may be an order of magnitude away from the real value.

Assuming you are sitting far away and you get a faint signal of Lada checking her voice in preparation for a concert and are tasked with judging whether Lada can break an eardrum with that or not. Obviously a single Lada fan in Norway who would love her to break the eardrums of all people in the concert may not get confirmation that she is capable of doing that from his microphone reading her signals at distance.

So the Norway fan cooperates with a 99 other fans all over the world who all listen for Lada's voice and all get a signal. Some signals are stronger and some are less strong. The only way they can judge whether she can break those eardrums or not is if they have a prior recording of Lada in a previous concert where eardrums were known to have been broken and they can compare the 2009 signals with the 1992 signal and assign some relative value to Lada's voice-strength. Obviously even the single Norway fan can do that if he had the 1992 recording, but by cooperating with his 99 pals he can get a much better reassurance about Lada's capabilities.

But if all 100 Global Golmal fans of Lada did not have a definite value for the 1992 concert recording they would still be in the dark about Lada's voice in 2009. The best they can do is to compare Lada's signals with signals they have got from concerts of other artistes in the US and other nations where eardrum breaking concerts have been popular in the past.

But they really need to be sure that the eardrum breaking values that they have for concerts in all those countries are accurate. But fans who actually attend concerts are possessive deaf-mutes and never tell others exactly how eardrum breaking each concert is. The cryptically state that they do not reveal the real values measured from sampling within the cavity of the singer's voice box.

Don't you think that the 100 Global Golmal Fans of Lada are up a gum tree when they seek reassurance of Lada's real capability?
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by samuel »

If they don't got the medium, then they got huge bars. You can do them a favor by telling them use nevada test site, not finkelstein river, but yup, gum tree is almost right. You should investigate how they use expensive gravity and magnetometric measurements around the planet to obtain prior information, and you should also look at statistics they've collected from various sources (earthquakes) to use in a probabilistic model during inversion. But yes, for nukes, they'll have larger error bars, unless they have their own huge library of these nuke signatures that they can use -- sort of like identifying sub from sonar. How large would be worthy of study!

S
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by Satya_anveshi »

Amber G. wrote:On a lighter node - saw some where -
There is a lot of sizzle/fizzle debate about current Nobel Winner
I don't mean Obama but Venkatraman Ramakrishnan who was was born in Chidambaram, TN
Should we start the whole fizzle/sizzle debate again?
Not to trivialize the Nobel to the good scientist...but one can say that the clobbered H&D of Indian scientific community due to the BARC episode has now been restored to an extent in a weird way. After all we have a good circumstantial evidence of the Nobel's authenticity after Obama winning the prize.
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by shiv »

I think it was Oppenheimer who estimated atmospheric test yields by throwing pieces of paper in the air and measuring how far they were moved by the blast. And I think it was Feynman who estimated yield by fireball size.

But once testing went underground, yield estimation climbed the gum tree.
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by samuel »

shiv wrote: But once testing went underground, yield estimation climbed the gum tree.
that, i'd say is a bit of a generalization...
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by shiv »

samuel wrote:
shiv wrote: But once testing went underground, yield estimation climbed the gum tree.
that, i'd say is a bit of a generalization...

I have not yet been told why that generalization is wrong, if it is indeed wrong. That is why I brought up the subject. To learn.
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by geeth »

>>>I do see credibility in his claim , when he being an important member of POK 2 team and backed by eminent scientist and ex BARC/DAE chief like PKI and Sethna.

I have no problem, if you wish to believe Santanam, and may be you are right and I am wrong. I believe people who themselves are eminent in their field of work and have access to actual data. In other words, I do not consider them as liars.

>>>Sure these are weak arguments like he could have easily got a crater for S1 but did not since he wanted to hide , if he got a crater for S2 and didn't want to fool some one then S1 is not a issue at all.
>>>The GOI is just acting foolish by not publishing pics of Arihant , its not that we are first in the world to do it or something extraordinary that we are developing that the world has yet to see , they are just paranoid to the point of being naieve.

Since you are passing judgement on their action, you sure must be knowing what you are talking. I do not know, so no further comment.

>>>Ofcourse they have to hide it initially coz they got much of it from somewhere

Again, I hope it is not just speculation.

>>>Simulation based on what , what kind of data we had to simulate a TN that too a advanced TN as they claim they had done , they do test to check the consistency of the test and the paramaters evaluated , a lot of time in world and even in India the first test would succeed and second failed , had they been happy with only one test only it would be disaster in waiting.

Simulation can be done based on theoretical values, based on which design can be completed, and validated by actual testing. They have a number of reactors for theoretical/experimental studies.

>>>So the one test for TN is enough argument may not be good even if it is sucessful as a TD , for a military weaponised weapon they would need to do more than one test ( and perhaps 2 bare minimum as Santy says to qualify TN as a weapons for that specific design )

They have conducted a series of 5 tests. Nobody knows how many of them were for validation of TN design.

>>>Sure , he may even say computer simulation is enough no more test needed.

He has already said that...Given a chance, he would test again.

>>>But right now even the S-1 credibility is at stake.

In the minds of the believers of the New Order?

>>>If they (missile people) are given only one chance, won't they do as much as possible in one go? Here they have the luxury, so they conduct more tests. of course, if it fails in the first shot, then it will be tested again, before giving it to the user.

>>>Even the missile people know 1 test is not good enough even if 100 % successful ( they do bare minimum 3 test ) ,that too as recent Agni-2 test showed once batch production is tested things may not be as great as 3 successful test would indicate they do.

>>>Similary the nuclear weapon designer in the world do more than one test for a weaponised design ( not a capable one but a weaponised one )

As I said before, Missile tests cannot be compared to Nuclear tests. Having said that, Indian missile designers do a lot of simulation and keeps the number of missile tests to bare minimum.

>>>RC has been claiming from day one S-1 is successful no more test needed , so asking for more test is something did not arise.

Yes he said no more test needed for the same design..and we can't expect him to ask in public even if another is required. It is but logical to expect him to grab the opportunity, if he is given one. For that matter, what happened when he asked for conducting tests before 1998? was the permission given?

>>>And respectfully , I do not agree with this and nor does any where in the world is that the norm , unless ofcourse India is on another planet.

>>>The key is to validate the paramaters across different trajectory and test its consistency , missiles can work great in 1 or 2 or 3 test and then fail when checked for consistency , something the Russian Bulava SLBM experienced

Let us keep the missile tests out - not relevant, or even comparable, because of the restrictive nature of Nuclear tests.

>>>Depends how serious how the GOI is about National Security , but looking at the situation we are in we are in denial and usual chai biscooot

That will continue for the foreseeable future. My present fear is, how MMS will handle the Nobel for Obama..will he take it sportingly, or stand in the queue for the next year's..? after all, peace prize is available year after year.
Last edited by geeth on 10 Oct 2009 10:16, edited 2 times in total.
samuel
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by samuel »

Well that's because, I think,
a) it depends whose yield you are estimating yours or someone else's. I think e.g. US has good estimates of its own yields.
b) what the error bar is -- I mean 20KT+/-10KT is a huge error, 200KT+/30KT is not.

It would be great to look up some seismic work, "open loop" the methods are similar. Like how effective the gravity or magnetometry data or other synoptic surveys is in constraining the error bars, how testing with nukes with similar devices/tonnage in your own country might give you some prior information for elsewhere. I am not sure the error is 10% (or X%) irrespective of magnitude.


S
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by Amber G. »

shiv wrote:I think it was Oppenheimer who estimated atmospheric test yields by throwing pieces of paper in the air and measuring how far they were moved by the blast. And I think it was Feynman who estimated yield by fireball size.

But once testing went underground, yield estimation climbed the gum tree.
It was Fermi who threw bits of paper (and his estimate came out to one of the best)..
Feynman was the one who (prob. the only one) saw the fireball by directly looking at it (standing behind a windshield of jeep - and confident that UV rays would be absorbed by the glass - He did not look in other direction with dark glasses on as they were ordered to do - At least that is what RPF used to tell)

Also, BTW one of the most accurate estimations of yield of Hiroshima and Nagasaki bombs came from post event measurements (courtesy of famous Japanese nuclear physicist Nishijima) at the site(s).
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by Amber G. »

samuel wrote: b) what the error bar is -- I mean 20KT+/-10KT is a huge error, 200KT+/30KT is not.
To put it mildly, 'huge' is quite a bit of ambiguity if you are quantifying like this. In some aspects of nuclear physics (it is well l known) even 1000% "error" was/is *not* considered "huge" ("Same order of magnitude" is considered very good) while , for example, for my GPS even 1 in a million (nay 1 in trillion ) error is unacceptable. Trick is not to plug in blindly, values given in a formula and get a value with more significant figures than called for. In many calculations shown here in BRF, one has lost sight of this.
It would be great to look up some seismic work, "open loop" the methods are similar. Like how effective the gravity or magnetometry data or other synoptic surveys is in constraining the error bars, how testing with nukes with similar devices/tonnage in your own country might give you some prior information for elsewhere. I am not sure the error is 10% (or X%) irrespective of magnitude.
Would be great, so why don't you (generic you) give us the "open loop" etc and constrain those "error bars" .. How about the equation which has been used here quite a few times (R=K*Y^(1/n) ... How about giving some values for R/K/n etc?

Instead of just talking about "synoptic surveys"... can we have some data?

Thanks.
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by NRao »

As a FYI, before we get too much into yields and detection systems:

Nuclear weapon yield
Calculating yields and controversy

Yields of nuclear explosion s can be very hard to calculate, even using numbers as rough as in the kiloton or megaton range (much less down to the resolution of individual terajoule s. Even under very controlled conditions, precise yields can be very hard to determine, and for less controlled conditions the margins of error can be quite large. Yields can be calculated in a number of ways, including calculations based on blast size, blast brightness, seismographic data, and the strength of the shock wave. Enrico Fermi famously made a (very) rough calculation of the yield of the Trinity test by dropping small pieces of paper in the air and measuring at how far they were moved by the shock wave of the explosion.

As a consequence, in a number of cases, precise yields have been in dispute, especially when they are tied to questions of politics. The weapons used in the atomic bombings of Hiroshima and Nagasaki , for example, were highly-individual and very idiosyncratic designs, and gauging their yield restropectively has been quite difficult. The Hiroshima bomb, " Little Boy ", is estimated to have been between 12 and 18 kt (a 20% margin of error), while the Nagasaki bomb, " Fat Man ", is estimated to be between 18 and 23 kt (a 10% margin of error). Such apparently small changes in values can be important when trying to use the data from these bombings as reflective of how other bombs would behave in combat, and also result in differing assessments of how many "Hiroshima bombs" other weapons are equivalent to (for example, the Ivy Mike hydrogen bomb was equivalent to either 867 or 578 Hiroshima weapons — a rhetorically quite substantial difference — depending on whether one uses the high or low figure for the calculation). Other disputed yields have included the massive Tsar Bomba , whose yield was claimed between being "only" 50 Mt or at a maximum of 57 Mt by differing political figures, either as a way for hyping the power of the bomb or as an attempt to undercut it.

Nuclear testing yields, as in the Tsar Bomba example, can also be used as a way of reflecting upon technical expertise, and claiming higher yields or accusations of lower yields can be used as a way of promoting or disparaging the technical abilities of a nuclear program. When India claimed to have successfully detonated a hydrogen bomb in their 1998 Operation Shakti tests, many Western observers relied on analysis of seismograph ic data to determine whether or not the Indian tests reflected a successful hydrogen bomb detonation. Some have alleged that India's reported yields have been higher than their actual test yields, a move which would apparently be for political purposes (to claim more nuclear ability than their rival Pakistan , for example, or to demonstrate their military might to other potential rivals such as nearby China ) if true.
Calculating yields and controversy
Yields of nuclear explosions can be very hard to calculate, even using numbers as rough as in the kiloton or megaton range (much less down to the resolution of individual terajoules). Even under very controlled conditions, precise yields can be very hard to determine, and for less controlled conditions the margins of error can be quite large. Yields can be calculated in a number of ways, including calculations based on blast size, blast brightness, seismographic data, and the strength of the shock wave. Enrico Fermi famously made a (very) rough calculation of the yield of the Trinity test by dropping small pieces of paper in the air and measuring at how far they were moved by the shock wave of the explosion.

A good approximation of the yield of the Trinity test device was obtained from simple dimensional analysis by the British physicist G. I. Taylor. Taylor noted that the radius R of the blast should initially depend only on the energy E of the explosion, the time t after the detonation, and the density ? of the air. The only number having dimensions of length that can be constructed from these quantities is:

Using the picture of the Trinity test shown here (which had been publicly released by the U.S. government and published in Life magazine), Taylor estimated that at t = 0.025 s the blast radius was 140 metres. Taking ? to be 1 kg/m³ and solving for E, he obtained that the yield was about 22 kilotons of TNT (90 TJ). This very simple argument agrees within 10% with the official value of the bomb's yield, , which at the time that Taylor published his result was considered highly-classified information. (See G. I. Taylor, Proc. Roy. Soc. London A201, pp. 159, 175 (1950).)

Where this data is not available, as in a number of cases, precise yields have been in dispute, especially when they are tied to questions of politics. The weapons used in the atomic bombings of Hiroshima and Nagasaki, for example, were highly individual and very idiosyncratic designs, and gauging their yield retrospectively has been quite difficult. The Hiroshima bomb, "Little Boy", is estimated to have been between (a 20% margin of error), while the Nagasaki bomb, "Fat Man", is estimated to be between (a 10% margin of error). Such apparently small changes in values can be important when trying to use the data from these bombings as reflective of how other bombs would behave in combat, and also result in differing assessments of how many "Hiroshima bombs" other weapons are equivalent to (for example, the Ivy Mike hydrogen bomb was equivalent to either 867 or 578 Hiroshima weapons — a rhetorically quite substantial difference — depending on whether one uses the high or low figure for the calculation). Other disputed yields have included the massive Tsar Bomba, whose yield was claimed between being "only" or at a maximum of by differing political figures, either as a way for hyping the power of the bomb or as an attempt to undercut it.
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by samuel »

Amber G.

All that is well and good, but can you say how a 100% error bar on any yield can be a useful system? I am quite familiar with less than order of magnitude type of errors being ok especially when "non-dimensionalizing" for various things, but from an engineering point of view, that is almost never good enough.

Sure, let's get the data we need, and I will post as it comes available.

Thanks
S
PS: Geez, this guy GI Taylor shows up everywhere. Very talented fella.
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by NRao »

From what little I have read, it seems to me, that the political and deterrence "groups" has adapted to the inability of the scicom to come up with precise means/methods of predicting a yield. So, right now, it really does not matter. Those depending on the scicom are more than happy with a +/-10% and I would not be surprised if they will tag along even with +/-25% or even more.
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by svinayak »


Dr Ramanna, the driving force behind what for long was called India’s first “peaceful nuclear explosion” in May 1974, himself opened the veil to assert India’s nuclear capability. Speaking at a function in Pune in October 1997, Dr Ramanna was asked whether India could make an atomic bomb. “I can tell you now,” he said, “1974 was an atom bomb.” The statement made front page headlines in newspapers across the world. The most important fallout of Dr Ramanna’s bold declaration was that it forced the country’s policy makers to openly acknowledge India’s nuclear prowess and capabilities as an “atomic power” and accept the responsibilities that came with that.

Within seven months of Dr Ramanna’s statement, India went ahead with a series of nuclear tests at Pokhran, in May 1998.
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Re: Pokhran II not fully successful: Scientist - Part-3

Post by Amber G. »

Shiv - Nice post. As always enjoyed it.
NRao - Thanks, well put. BTW this is what I was trying to say. One really can't take a magic formula
and plug values in without understaning how relible and precise the theory behind the formula is.

Samuel-
I am quite familiar with less than order of magnitude type of errors being ok especially when "non-dimensionalizing" for various things, but from an engineering point of view, that is almost never good enough.
Honestly boss, sorry but I absolutely can not make any sense out of the above... particularly exactly what do you mean by ""non-dimensionalizing" for various things," in this context. Hope you elobrate.

Any way following could be a little general type of comment -- hope it clarifies some part.

When a nuclear physicist gets happy that his theory and experiment are in agreement some times (actually lot of times) the agreement comes out to be 'same order of magnitude. In other words, if , say, theory predicted 50 one is happy if the experiment gave a value between 5 and 500 (as long as it did not give a disagreebale value like 50000)

(Error between 50 and 500 is about 1000% much more than 100%)

Yet those values are and have been helpful. For example when, for the first time they were trying to find such elemantry things like 'critical mass' or amount of graphite they would need for the first U-reacter (purely engineering type views).. the initial experiments yielded only very rough values.

(Famously General Grover (Manhatan Projects top military general) once complained to the scientists - "It's like asking me to plan for a dinner party and you tell me that there are about 20 guest and I have to assume it can be anywhere between 2 and 200 ... how one is supposed to plan for that" )..

Anyway my point here is, some of the methods (specially to use pure sesmic type data to calculate yield) could easily introduce errors and extimates could have quite a bit of uncertainites. 50% error may be pretty bad for one kind of method, but could be norm for other.

Sorry for the long post. Hope it helps some.
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