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Subject: Britain may replace Trident--
Herc the Merc    11/26/2006 5:29:41 PM
NUKEWARS Britain To Unveil Plans To Replace Nuclear Missile System File photo: Trident missile launch. by Staff Writers London (AFP) Nov 22, 2006 Britain is to publish proposals by the end of the year on how to replace its ageing nuclear deterrent Trident missiles, Prime Minister Tony Blair told lawmakers Monday. Blair confirmed a question from the leader of the smaller opposition Liberal Democrats Menzies Campbell that the government's position on whether to maintain the Trident missile system would be set out by the turn of the year. He also said he was "sure" lawmakers would get a chance to vote on the issue. "I believe it is important that we maintain the independent nuclear deterrent," he told Campbell during the weekly "prime minister's questions" in the lower chamber House of Commons. The issue of whether to scrap Trident -- which will become obsolete with the four Vanguard class submarines that carry them in the mid-2020s -- is a deeply divisive issue among Blair's governing Labour Party. Scrapping nuclear weapons -- and also nuclear power -- was a totemic issue for the left-wing party in the 1980s but the policy was dropped before the 1997 general election, when Blair's revamped centre-left "New Labour" was elected. Instead, its manifesto pledged to retain Trident. Blair's likely successor, finance minister Gordon Brown, has previously said he, too, is in favour of keeping Britain's nuclear deterrent. But a number of senior ministers, including Foreign Secretary Margaret Beckett, reportedly have concerns about it. Anti-nuclear campaigners are currently lobbying hard against any replacement, including via an online petition on the prime minister's own website. By Wednesday, there had been more than 2,000 signatories supporting the motion: "We the undersigned petition the Prime Minister to champion the Nuclear Non-Proliferation Treaty, by not replacing the Trident nuclear weapons system."
 
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paul1970    nuclear weapons   12/8/2006 5:47:37 AM
if you agree that Britain needs nuclear weapons for defense then it simply has to be independent, capable of surviving a first strike by a hostile nation and still be able to deliver a blow that leaves the opposition in no shape to continue the action.
 
the only way of doing this is with SSBN's.
 
 
disagreeing is fine but I for one think we need them.
 
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lightningtest       12/8/2006 10:24:38 AM

Lightningtest:
I spend my workday doing calculations and research, I'm not going to do yours in my free time. If you want to prove it (noting that "Prove" derives from "test") then go find that stuff from the wonderously diverse internet.

Although I'll point out that you also have to get your gamma-ray detector into orbit, sufficiently shielded that cosmic rays don't foul up its sensitivity and in an orbit that allows it to keep watch on whatever it's looking at.

.....

The power output of the reactor (I assume 600MW(th) [Ref 1]) we must know in eV;
 
2.2E+22 eV/J x 600E+6 J/s = 1.32E+28 eV/s 
 
The average amount of energy released from a U-235 fission I take to be 215E+6eV [Ref 2],  I assume one gamma ray (ph) is emmited per fission;
 
1.33E+28 eV/s / 215E+6 eV = 6.14E+19 ph s-1.
 
The ratio of 1cm square sensor in GEO relative to the surface of a sphere of 35786km radius;
 
0.01*0.01 / 4*pi()*(35786E+3 m) ^2 = 1E-4 / 1.61e+16 = 6.21E-21
 
6.14E+19 * 6.21E-21 = 0.38 ph cm-2 s-1
 
Note the figure above is when reactor running at 100%.  How significant is this...
 
The next state of the art detector when operating in a mode designed to characterise and localise a gamma signal is decribed thus [3];
 
Source localization less than 5 arcminutes for sources of strength > 10-8 ph cm-2 s-1 (10 times fainter than EGRET) and less than 0.5 arcminutes for strong sources to facilitate counterpart searches at X-ray and lower energies."
 
If we assume the sub appears as only just as a "strong" source emmiting 1000 times more gamma rays than the minimum detectable source (i.e. strong >10-5 ph cm-2 s-1) the time required to detect a single gamma ray from the sub reactor is 105 seconds (~28 hours).
 
As the sub may move at ~30 knots for that wholse time and potentionally travel ~1600km the only way to detect a sub on the move is if the required time to detect a gamma ray from it is much less than 28 hours,  it must be of the order of minutes.  A count rate of 10-2  I think would suffice to locate a moving sub.  The margin in (dB) between the signal (unattenuated) and the required detector performance is now;
 
20*LOG(0.38/0.01) = 31.6dB
 
31.6dB isn't much margin when considering the gamma rays must traverse the reactor shielding, sub skin, seawater and atmosphere and still 1 in 38 must make it to GEO and the detector.  So at present the system isn't feasible even if as flamingknives said ;
 
"you also have to get your gamma-ray detector into orbit, sufficiently shielded that cosmic rays don't foul up its sensitivity and in an orbit that allows it to keep watch on whatever it's looking at."
 
However if the sub is moving more slowly the sensor data can be integrated for longer a more attenuated gamma ray flux can be detected.  If the sub stayed put for over a day, and runs its reactor at ~20% a  fix may be obtained even with ~78dB of attenuation of the gamma rays from the reactor by the reactor shielding, sub skin, seawater and atmosphere.
 
20*LOG((0.2*0.38)/ 0.00001) = 77.6dB
 
How good could the fix be given near future technology, 1 arc minute when looking from GEO altitude to the nearest part of the earth is 
 
2 * pi() * 35786 km / (60deg x 60min) = 62km.
 
So if the attenuation along the path to GEO of ~1MeV to ~30MeV gamma rays emittied from a sub reactor is less than ~78dB I think the technology wil exist in the future to scan and locate reactors to ~30km, if they do not move very far each day.   The less the attenuation the quicker and more precise the fix.
 
The attenuation calcs still to be done;
I can't find the attuation calcs for the sea water and&n
 
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lightningtest       12/8/2006 12:09:01 PM
Given my assumptions that only the directly transmitted gamma rays get to the sensor.
 
Gamma rays of 6 MeV are attenuated to one tenth of initial level (20dB) by 4 inches of steel.

Gamma rays of 1 MeV are attenuated by one tenth of initial level (20dB) by 2 feet of water.

Gamma rays of 6 MeV are attenuated by one tenth of initial level (20dB) by 4 feet of water.

Even assuming at 36MeV 20dB of attenuation is provided by 6 feet of water then once the 4” thick sub skin is ~10 feet below the surface it is beyond the near future detection limit of gamma ray sensors in GEO orbit.   
I assumed in the previous post that none of the slightly scattered rays get to the sensor.  Even adding all those scattered rays into the mix probably at most increases the sensor signal by a factor of 60dB (or gains it an extra 12 feet of detection depth in the water at 6MeV).

 If the sub was 200ft down the water would attenuate ~36MeV Gamma by > ~50 x 20dB i.e. >1 x 10-50

Gamma ray sensors would have to improve over the state of the art by a factor 10 with 47 zeros behind it.  That might take longer than the design life of the next generation SSBN so it won’t be gamma ray sensors detecting the subs.

So unless the reactor is within ~8 feet of the surface and stationary for days -  gamma ray detectors are useless it seems.

 
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flamingknives       12/8/2006 12:55:08 PM
Wow. I think that's the first time I've ever seen someone use maths on the internet, and use it to prove themselves wrong.

Thank you, lighteningtest. One day I might be able to follow all of that too, but I'm an engineer, not a physicist.

ISTR something about tracking submarines by their wake on the surface, which was somewhat more feasible.
 
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lightningtest       12/11/2006 6:07:05 AM
I looked over the numbers I used again.  I made a error in my calc of detection precision.
 
"How good could the fix be given near future technology, 1 arc minute when looking from GEO altitude to the nearest part of the earth is 
 
2 * pi() * 35786 km / (60deg x 60min) = 62km."
 
This should be;
 
2 * pi() * 35786 km / (360deg x 60min) = 10.4km."
 
Also I was a bit presimistic on my derating of the sensor as I assumed it was only going to be 1cm square.  It'll probably be about 1000 cm square or maybe more.
 
This and the fact that scattering of gamma rays reduces as their energy decreases up to the point  pair production kicks in means that we will probably gain as extra 90dB of margin in the sensor and gain about 2 more feet per 20 dB (i.e. ~50MeV gamma rays attenuated by one tenth of initial level (20dB) by 8 feet of water.
 
So potentionally a slowly moving sub could be detected down to ~40 feet using near future tech.  That might be periscope/antenna depth I don't know.  In about 20 years that detection depth might be ~50ft.
 
I don't have a problem admitting when I blow bubbles....the consequences of not admitting mistakes in a timely manner are generally quite severe in my line of work.
 
 
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lightningtest       12/11/2006 6:33:12 AM
2.2E+22 eV/J is wrong, actually   6.24150974 × 1018eV per Joule,  that changes thing for the worst somewhat as I guess nobody listening pointed it out cause they couldn't be bothered, nuff said.
 
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flamingknives       12/11/2006 2:21:04 PM
More like I wouldn't have a clue as to what the correct value would be.
 
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EssexBoy    Will the US oblige?   1/13/2007 2:23:57 PM
Does anybody know if the US have indicated that they will sell us the Trident replacement?
 
All our discussions could look a bit daft if they tell us to sod off.
 
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Yimmy       1/13/2007 5:52:52 PM

Does anybody know if the US have indicated that they will sell us the Trident replacement?

 

All our discussions could look a bit daft if they tell us to sod off.



Well.... what with their telling us to sod off, and the associated end of the British nuclear deterrent (and with it our ultimate ticket to defence, freedom et al), I guess we will just have to shoot off all our missiles at the end of their shelf life and end the world.... otherwise someone may go and blow us up when we don't have the missiles to counter with!

 
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flamingknives       1/13/2007 6:20:09 PM
Christ, Yimmy, don't say things like that. someone might think it the most "cost-effective solution".
 
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