[alancalverd]

Civil liberties have taken some punishment

which appears to have been part of  the objective - to impose a police state on a democracy. The other objective, to start a war between civilisation and Islam, seems also to have been achieved. A brilliant plan, superbly executed, and the idiot Bush fell right into the trap. Which wouldn't matter if he hadn't dragged the rest of us in with him.   

[syhprum]

The 911 bombers were Saudi's protesting  about America's behaviour in Saudi Arabia so what was the American reaction we can't attack Saudi Arabia as it is a valuable market for our armaments and a source of fuel so we will attack Iraq instead.

[evan_au]

population of Hiroshima, and certainly none of any military significance.

I understand that Nagasaki was a military port, but the mountainous terrain limited the damage done by a single bomb.

Hiroshima was not a significant military target, but its flat terrain and large population turned it into a nuclear target.

[Malamute Lover]

Necromancy at work here. But I was advised that this was OK if I have something meaningful to say. Which I do. (I hope)

there is however a limited size you can make this as the bomb tends to blow itself apart before it has all ignited.

Yep. I believe only about 4% of a simple Uranium or Plutonium bomb is fissioned before the bomb had undergone 'self-disassembly'...

Practical efficiency of a fission bomb is about 25% but is usually less. The Fat Man plutonium bomb used on Nagasaki had an efficiency of about 17%. The Little Boy uranium bomb used on Hiroshima was very inefficient and had an efficiency of about 1.4%.

The much greater efficiency of Fat Man was due to:

@ The use of plutonium, with its much higher spontaneous fission rate

@ The faster assembly and greater compression of the implosion design versus the Little Boy gun design

@ The natural uranium (unseparated isotopes) tamper that helped slow the expansion of the plutonium undergoing fission, increasing efficiency, and by absorbing neutrons, converting some of the U-238 to Pu-239 (or even fast fissioning Pu-240) which then underwent fission when more neutrons were absorbed, along with the small U-235 component.

Before developing the true hydrogen bomb, there was the boosted fission design that added lithium 7 deuteride to the stew. The lighter atoms helped slow down the neutrons that were flying around to make them more readily absorbed by the plutonium. In addition, lithium is a rare case of a nucleus sensitive to high temperate (about 100,000 K) then breaking up into 2 atoms of tritium and a neutron. Some of the tritium and deuterium will undergo fusion releasing some energy and more neutrons. All these extra neutrons will lead to more plutonium undergoing fission, boosting yield.

Fusion bombs only work at very high temperature conditions, so generally use the x-rays released by a fission explosion to give conditions for 'ignition'. The bigger bombs have a layer of fissionable material outside the fusion bomb to increase the yield so you get a fission->fusion->fission explosion. Not sure if the biggest bomb dropped in the atmosphere (Soviets, 47Megatonnes TNT-equivalent) was this type or not but if gives you a feel for it - 3000 times the 15 kilotonnes explosion at Hiroshima.

The natural uranium tamper used in three stage nuclear weapons works on the principles described above, which also apply to fusion processes.  The Soviet RDS-220 Tsar Bomba used lead in the third stage tamper. Uranium has a density 80% greater than lead so the tamping was less efficient. The point of using lead was that a uranium tamper in a device this size would have increased yield to about 100 MT but created enormous quantities of fallout over populated areas. Since the actual yield was almost exclusively from fusion, this was in fact a very clean event in terms of fallout.

The explosive yield was originally estimated by Western experts as 58 MT based on seismic data. Many years later, after the breakup of the Soviet Union, Russian scientists released a figure of 50 MT. This was a truly gigantic explosion and the mushroom cloud shape was readily visible 160 km away, having risen to a height of 65 km.

Hard to understand why anyone would want or need an explosion that big...?

The main purpose was clearly propaganda, intended to intimidate new US president Kennedy, who had earlier that year (1961) attempted an invasion of Cuba, then a recent addition to the ranks of Soviet allies.

The Soviets were interested in very high yield devices not as city busters as might be thought but to be used against US Strategic Air Command wartime HQ under 3000 meter tall Cheyenne Mountain in the Colorado Rockies. Construction had been initiated by President Kennedy early in 1961. SAC controlled the B-47 and B-52 bomber fleets and US ICBMs.

The Tsar Bomba weighed 27,000 kg and could only be carried by a modified Tu-95 ‘Bear’ turboprop bomber with some of its fuel tanks removed to make room. This was clearly not a viable delivery system. However, years later a 28 MT warhead was developed for the Soviet R-16 ICBM (NATO reporting name SS-18 Satan).  This missile was capable of delivering its payload anywhere in the world. A warhead of this size would make a crater over 300 meters deep in solid rock and send a gigantic seismic wave through the mountain.

Consider that Hiroshima was in the mid to end 1940's, this Soviet bomb was  at least 20 years after that. Now consider that its been aproxomatly 40 years since the Soviet bomb, thats double the time it took the to make a bomb 3000 times the size of hiroshima, imagine a bomb 6000 the times of the soviet bomb, thats what we could have now but we wont ever see the explosion of one of those bombs unless it is used in a war because most countries including the united states and the former USSR.

The Tsar Bomba was detonated on October 30, 1961, a little over 16 years after Hiroshima. It remains the most powerful nuclear device ever made. Technology has concentrated on smaller and lighter weapons, on tactical weapons and on specialty devices like neutron bombs and focused microwave emitters intended to fry electronics.

Also in response to the why would you need such a large bomb question, the Soviets spent their resources making bigger bombs whereas the united states used their money to make accurate bombs, basically the soviets were going under the possibility of why guide a bomb to one house you needed destroyed if you could blow up the whole city and be done with it

In the 1950s, the US concentrated on making nuclear weapons smaller and lighter so that they could be carried by missiles. The Soviet Union concentrated on making bigger missiles. Targeting weapons against objects the size of a house from great distances did not really become feasible until the 1980s and then in cruise missiles, not ballistic ones. The GPS guided strategic version of the Tomahawk jet powered missile could be launched from a submerged submarine off the coast of New York City and hit a garage door in Chicago.

population of Hiroshima, and certainly none of any military significance.

I understand that Nagasaki was a military port, but the mountainous terrain limited the damage done by a single bomb.

Hiroshima was not a significant military target, but its flat terrain and large population turned it into a nuclear target.

Hiroshima had a large Army depot and an active port. Nagasaki was a major producer of naval ordnance and had a port used by the Japanese Navy. However, by that time Japan no longer had a Navy to speak of. But a major consideration of target choice was impact on civilian populations. Tokyo was no longer worth bombing, having 70% of it already burned to the ground by B-29 fire bombing, no military value anymore and mostly abandoned.

Here is an interesting article on how the nuclear bombing targets were chosen.
https://www.theatlantic.com/international/archive/2015/08/hiroshima-nagasaki-atomic-bomb-anniversary/400448/

Interestingly, one of the selection factors put forth in early May 1945 was that a proposed target was “likely to be unattacked by next August”. Anyone know why August was significant?