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yield figure

Bomb designer Ted Taylor in John McPhee's The Curve of Binding Energy claimed that the Super Oralloy Bomb's yield was "in the megaton range". Where does the 500kt figure in the article come from? Should Taylor's figure also be mentioned? Phr 10:01, 24 February 2006 (UTC) reply

  • The 500kt figure is used in every reputable source (i.e. Hansen's U.S. Nuclear Weapons, Sublette's NuclearWeaponsArchive.org, etc.). I think we can chalk up Taylor's off-hand comment as either being 1. exaggeration, 2. overly vague, or 3. incorrectly transcribed by McPhee, because there is nothing out there which puts it above 500kt. -- Fastfission 21:18, 25 March 2006 (UTC) reply

Various sources claim the British pure fission bomb designed at the same time as Green Bamboo and Orange Herald (both boosted weapons) had a yield of about 1 MT. I am not sure how accurate this is, but it is worth looking up. Maury 00:50, 1 June 2006 (UTC) reply

If they were boosted weapons, then they were not pure fission bombs, by definition. -- Fastfission 01:18, 1 June 2006 (UTC) reply
Well the two I mentioned were boosted, but there was a third design as well that was pure fission. There's not much detail, but look here, in the section between Totem and Mosaic: http://nuclearweaponarchive.org/Uk/UKTesting.html
I see what you mean. It doesn't seem that they actually developed it, though. It also just occurred to me that the entire thing here has been about the phrase "in the megaton range", which didn't click before — I recall reading somewhere that anything from 500 kt upwards was considered "in the megaton range" by the bomb designers (had to do with order of magnitude or something like that, not whether it was actually 1 Mt or not). I haven't the foggiest idea where I read that, at the moment, but I seem to recall it from somewhere, which would make Ted Taylor make more sense. -- Fastfission 13:55, 1 June 2006 (UTC) reply

Additional input, hopefully useful.

The British Green Bamboo design was abandoned before testing. The Orange Herald device was 'core-boosted' according to the official history published 2001. ISBN  0-312-23518-6 in North America, ISBN  0-333-94742-8 elsewhere. A verbatim passage from a post test account on page 147 might be helpful here.

  • Quote: "The yield of Orange Herald (small) was estimated at 700-800 kilotons, a record for a pure fission weapon. But it was uncertain [to AWRE scientists] whether there had been any boosting effect at all, or whether the yield was all due to fission of uranium-235. It was very close to Corner's [an AWRE physicist] estimate for an unboosted yield. Back at Aldermaston the WDPC thought the boosting had failed because of Taylor instability and further work on core boosting by this method would be pointless. Hulme [another AWRE physicist] thought it would be a mistake to assume that there had been any contribution at all from the boosting."

Quote ends here.

There is much confusion about the claims of up to 1 Mt yield. That was for the Brits a target figure. They hoped to achieve 'one megaton in one ton' to quote the official history, because Orange Herald was intended as an interim warhead for the Blue Streak MRBM. To shoehorn it into the weight and size limits for the missile it had a smaller diameter HE implosion design than the similar Green Bamboo, and to compensate for the expected reduced compression at the core, the amount of HEU in the hollow core was increased significantly. No hard evidence of the core weight exists, but declassified files relating to HEU cost for that specific core have been declassified in London. Matched against other hard evidence of cost per kg it has been possible to compute reasonably accurate figures for the Orange Herald core size as approx 97-125 kg of HEU. It was because these Orange Herald warheads would hoover-up scarce fissile material that they could only be contemplated for the Blue Streak missile, until a thermonuclear alternative became available. But at that time, the UK had not yet re-discovered the Teller-Ulam concept, and were not able to design a thermonuclear device. Brian Burnell 16.05, 06 June 2006 (UTC)

Most excellent info. I am still somewhat confused by the wording though, notably the "a record for a pure fission weapon" portion. Is this passage suggesting that it would have been a record for... or that it was a record for...? The following sentances futher confuse me, as it seems to suggest there was some boosting, but it didn't work? Maury 17:55, 6 June 2006 (UTC) reply

It was a record

My reading of the official history, written by Lorna Arnold (a noted Oxford physicist) for the Ministry of Defence, was that it 'was' a record. When she wrote this in 2001 she had access to previously classified data. Note also the disparity in the quantity of 90-125 kg of HEU in the Orange Herald core compared with the published figure of 60 kg of Ivy King, published many years earlier by Chuck Hansen. The AWRE physicists Corner and Hulme, and possibly others who do not appear in Arnold's account, and the Weapons Development Policy Committee (WDPC) were all of the opinion that the boosting had failed to work, and that the entire yield was ascribed to fission. I could ask the technical historian at AWE (Kate Pyne) for her view on this if it thought useful. A useful benchmark might be the study done for the Zodiak Mk.3 pure fission bomb to yield one megaton. The study concluded that 120 kg of HEU would be required with the higher core compression obtained from a much larger HE implosion sphere than Orange Herald's.

There is no doubt in my mind that at the official figure of 720 kT, the Orange Herald pure fission yield puts Ivy King in the shade.

The Orange Herald core size is computed from declassified documents that priced weapons grade HEU at a cost to AWRE and the RAF at £28'000 per kilo in 1956-57. Other declassified documents put the cost of fissile material in the Orange Herald core used at the Grapple test at £3.5M. Ergo, 125 kg. Some historians believe it may have been a little less at 90 kg; but there is no direct evidence for either.

If HEU cost seems very high, it can be ascribed to the small output of the British programme that pushed up costs; and also that 1956 was the first year of output. In following years the cost fell as the book value of the capital plant declined. In the UK, fismat output was by the AEA Industrial Division that had been set up as a self-contained entity outside direct government control. Its finances were arranged as an independent entity, with its own pension fund, HQ staff costs etc; so in effect it was financed as a business, with the sole stockholder being the Treasury. Treasury accounting rules insisted that the supply of fissile material be paid for by government depts in the same way as they would pay a shipbuilder for a warship. At the full cost, plus a return on (the Treasury's) capital. So the cost of fissile material seems high as compared with other national programmes. It seems perverse. But these are bean counters. Cut them some slack.

I hope this helps. If I can help with any other matter please ask, but I'm more likely to see it for a quick response if you use my Talk page. Brian.Burnell 17:06, 7 June 2006 (UTC) reply

[[:Image:Orange Herald warhead.jpg|thumb|left|250px|The "Orange Herald" warhead. The tubular bulkheads are 62 in dia and give a sense of the scale of the Orange Herald sphere. Photoanalysis techniques suggest that the sphere measures 36 in dia, which co-incides with that specified in the operational requirement OR.1142. The Green Bamboo and Green Grass spheres were 45 in dia. That suggests that Orange Herald used over 700 kg less HE than the larger spheres, and less HE = less core compression = more HEU to maintain a given yield. As in the text. Brian.Burnell 12:34, 11 June 2006 (UTC)]] reply

'Anything over 500 kT was considered to be in the megaton range'.

The term 'anything over 500 kT was considered to be in the megaton range' was not based on science, but was merely a 'political-fix' by AWRE when they were under intense pressure to deliver an 'Interim Megaton Weapon' (in U.S. terminology, an Emergency Capability weapon). AWRE cobbled together an untested hybrid named Green Grass with elements of Green Bamboo and Orange Herald housed in a Blue Danube carcass and named it Violet Club. AWRE then estimated its yield at 500 kT to satisfy their political masters in Whitehall. The Air Force were not amused when after Whithall's attention shifted elsewhere, AWRE reduced their estimate to 400 kT. But the myth that 500 kT = 1 Mt had been created, and officialdom being officialdom it stuck. Rather like how inaccurate information on the web can be regurgitated and regurgitated indefinitely. I wouldn't think that Ted Taylor was aware of what was a purely British piece of sleight-of-hand by AWRE.

Hope this is helpful. I intend to upload shortly, a very good pic of Orange Herald installed in the centre section of a Blue Danube carcass with the panels, nose and tail removed. Brian Burnell 16.05, 06 June 2006 (UTC)

And see Violet Club. Brian.Burnell 12:33, 16 August 2006 (UTC) reply

British pure fission 1Mt bomb

There was a 1953 study produced for a pure fission 1Mt bomb fuelled by 120 kg of HEU but it never got beyond the realms of a project study. It was known as the Zodiak Mk.3 Bomb, and the only details can be found in a declassified document in the National Archives, London. Having looked at it myself, as far as I can recollect, it was no more than a panic response to news reports of the U.S. Ivy Mike detonation. I have a photocopy of the relevant bits of the documents. If you are desperate for a look I could scan and email a copy via my Talk page. Brian Burnell 16.25, 06 June 2006 (UTC)

Why no fusion?

Fusion was the target of this test. Why is there nothing about that in the article? The question would be: "How did they try and why did it fail?" -- 90.136.84.66 ( talk) 21:04, 13 February 2013 (UTC) reply

Fusion was not a target in either the Ivy King bomb or the British Green Grass/Violet Club bomb. The British wanted a 'high-yield' weapon in the megaton range and at that time had not successfully tested a true thermonuclear device, or understood the Teller-Ulam process that would make it possible. The large fission bomb was an insurance policy, an imperfect empirical solution, to fall back to just in case they continued to fail to develop a true thermonuclear weapon. It was never intended to be a fusion device, and neither was Ivy King Both were 'political fixes' to enable politicians to save face saying "we have a very big bomb". I can't speak about the American political objectives, but in the British case, after seeing hundreds of declassified government papers of the period, that was the objective. As things turned out, neither the Americans nor the British needed these large fission weapons because they succeeded in designing and testing true thermonuclear bombs.
There were other bombs such as Orange Herald and Short Granite (both British} that were at the time described as thermonuclear; but not really so by the terms we use today. Now, we classify these sorts of weapons as boosted fission bombs, because like almost all modern weapons the fusion boosting process employed only contributes a fraction of one percent to the total yield. These 'boosted fission' weapons were not thermonuclear at all. The Americans and Soviets went through a similar phase; not then fully understanding the underlying physics. I hope this helps. George.Hutchinson ( talk) 13:09, 31 July 2013 (UTC) reply
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