What's the highest yeild that could be got from a nuke?

[Hammer]

The most powerful nuke ever designed, the Tsara Bomba, would have had a yield of 100 MT. However in order to greatly reduce the radioactive fallout, the tertiary (and possibly the secondary) stage had their uranium replaced with lead.

This brought the actual yield down to 50-something MT.

But what I want to ask is: What is the maximum yield that would be attainable with regualar thermonuclear weapons as we know them today? What is the highest yield any nuke could be made to have?

[Specialist]

250 MT with maximum efficient.

[Einhander Sn0m4n]

250 MT with maximum efficient.

Any calculations or other numbers to back that up? (No I do NOT want to start a Flame War. I want to keep this civil)

EDIT: I also think this thread would be better moved to the SLAM forum.

[phongn]

The most powerful nuke ever designed, the Tsara Bomba, would have had a yield of 100 MT. However in order to greatly reduce the radioactive fallout, the tertiary (and possibly the secondary) stage had their uranium replaced with lead.

Only the U238 tamper was removed (it was replaced by Pb, as you noted). The second stage was kept there. It was one of the cleanest detonations ever.

[phongn]

Also, do remember that all modern nuclear warheads use the fission reaction to get most of their power. The fusion reaction is really there to increase the efficiency (by compression) of the fission reaction.

[Enlightenment]

General belief among nuke weapons types is that multistage bombs can be scaled up to pretty much any size whatsoever. Scaling up a bomb is just a matter of adding more fission or fusion stages until the desired yield has been reached.

The only limiting factors are the availability of nuclear materials and the fact that a bomb which is too heavy (or large) to deliver is little more than a very, very expensive paperweight.

[Sea Skimmer]

Eventually shaping the nuclear material used might become impossible; the parts would just to too damn big to work with. However by the time that might happen we'd be at the gigaton range easily.

I've never heard of any limitations in the physics behind it all. With sufficient resources you should be able to build a nuke that would yield hundreds of Teratons if you wanted to.

[Asst. Asst. Lt. Cmdr. Smi]

Instead of building one big bomb, why not just a bunch of smaller ones?

There are a few problems, though. First, with casing, the bombs might take up more space than one big bomb with the same power of all the smaller ones combined. Also, if they're all dropped in the same place, the blast radius would be low, right?

[Andrew J.]

Well, how much uranium is there in the universe?

[phongn]

Instead of building one big bomb, why not just a bunch of smaller ones?

There are a few problems, though. First, with casing, the bombs might take up more space than one big bomb with the same power of all the smaller ones combined. Also, if they're all dropped in the same place, the blast radius would be low, right?

Well, with the amount of resources you've crammed into this huge bomb you'd probably get much more bang for the buck by making smaller ones.

[Grand Admiral Thrawn]

Science.

[Sea Skimmer]

Instead of building one big bomb, why not just a bunch of smaller ones?

There are a few problems, though. First, with casing, the bombs might take up more space than one big bomb with the same power of all the smaller ones combined. Also, if they're all dropped in the same place, the blast radius would be low, right?

Well, with the amount of resources you've crammed into this huge bomb you'd probably get much more bang for the buck by making smaller ones.

I'd be more concerned about the resources expended strengthening the bottom hull of an oil tanker or building a twenty engine bomber for delivery of the thing before I'd worry about efficiency in terms of end destruction.

[Grand Admiral Thrawn]

Instead of building one big bomb, why not just a bunch of smaller ones?

Which is precisly why most modern nukes are several megatons tops.

[Durandal]

Phong, as I understand it, hydrogen bombs use fission as a trigger for fusion. The fusion energy release comprises most of the energy release.

[Sea Skimmer]

Phong, as I understand it, hydrogen bombs use fission as a trigger for fusion. The fusion energy release comprises most of the energy release.

That was the original idea behind Fusion devices, but as it turned out it worked better to use Fusion to simply make the fission blast much more efficient and thus powerful for the weight. The result is that in modern bombs the Fission is the bigger blast, but requires the fusion stage to do so.

[Alferd Packer]

Phong, as I understand it, hydrogen bombs use fission as a trigger for fusion. The fusion energy release comprises most of the energy release.

That was the original idea behind Fusion devices, but as it turned out it worked better to use Fusion to simply make the fission blast much more efficient and thus powerful for the weight. The result is that in modern bombs the Fission is the bigger blast, but requires the fusion stage to do so.

Wait a tick, I is confused.

As I was to understand it, the fission device was used to superheat the hydrogen so the atoms have enough KE to overcome coulomb repulsion. So which stage is fired first? The fission stage, or the fusion stage?

[Durandal]

Most likely the fusion stage. Basically, they'd use the energy created in the fusion reaction to pump more neutrons into the Uranium at high enough speeds and densities to make more of the neutrons hit the uranium nuclei, thus increasing the number of splits and thereby increasing the energy release. This makes sense, since it's extremely difficult to keep a fusion reaction going outside of immense-pressure environments.

[Alferd Packer]

But with Uranium, slow neutrons cause better more splits. The faster the neutron, the more likely it'll pass through the nucleus before the uranium 'realizes' it and fissions.

And how do they start the fusion reaction to begin with? Conventional high explosives? I dunno if conventional explosives would get hot enough fast enough.

[Sriad]

Most likely the fusion stage. Basically, they'd use the energy created in the fusion reaction to pump more neutrons into the Uranium at high enough speeds and densities to make more of the neutrons hit the uranium nuclei, thus increasing the number of splits and thereby increasing the energy release. This makes sense, since it's extremely difficult to keep a fusion reaction going outside of immense-pressure environments.

I'm almost certain it's the other way around. Fusion only happens naturally when pressure/heat is intense IE in stars but Fission can happen anytime a neutron bumps into an element heavier than Iron good and hard... but I need to have supper and stuff so I can't give any referances.

I'll post some links to prove one of us right later this evening if no one beats me to the punch.

[Korvan]

This page has some good info on the various types of nukes.

http://nuketesting.enviroweb.org/hew/Nwfaq/Nfaq1.html

For the multistage fission - fusion varities, the page claims unlimited theoretical yields. I'd bet there's some engineering difficulties with ultra high yield nukes, but with enough testing... We're not really using the moon for anything right now, are we?

[data_link]

Actually, we are building a giant LASER on the moon with which we shall cause unspeakable destruction. The moon/LASER assembly has been termed the "Death Star."

[The Duchess of Zeon]

Wait a tick, I is confused.

As I was to understand it, the fission device was used to superheat the hydrogen so the atoms have enough KE to overcome coulomb repulsion. So which stage is fired first? The fission stage, or the fusion stage?

Most bombs today are Fission-Fusion-Fission devices.

[The Duchess of Zeon]

By Stuart Slade.

http://pub82.ezboard.com/fhistorypoliti ... c&index=17

There was indeed a quantum leap in device design between the early days of Model 1561 and modern devices. That leap was called Super, or, as its known now, the fusion bomb.

There's a buried catch in all this. We use a fission device to initiate a fusion device so people leap to the assumption that the yield of the fission device is only a small proportion of the assembly as a whole. After all, if we use a fission device with a stand-alone yield of (say) 50 kilotons to initiate a 500 kiloton fusion device, 10 percent of the yield comes from fission and 90 percent from fusion right?

Wrong.

Think about a fission device going off for a second; the explosive charges explode, initiating the device. They compress the core, pushing it over the critical mass for a given density and a chain reaction starts. That causes a massive energy release which explodes outwards, overcoming the inwards pressure of the original explosive charges and releasing - and in the process, blowing the unconsumed fissile mass all over the place.

Now, the greater the original compression, the smaller the mass need to reach a critical level. However, there's another effect, the outward release of energy is contained longer by the inward pressure of the HE blast and so the core stays together longer and more of it is consumed. Thats why there was such a big increase in yields in the 1940s. When we went from 16-point ignition to 32-point and then to 64-point, compression went up and efficiency followed. in short, the blast consumed more of the atomic fuel before blowing the rest all over the horizon. Going from 32-point to 64-point initiation doubled the yield while using 25 percent less fissile. One of the reason why gun-devices are so inefficient is that they don't compress the cores at all. They just unite them.

So suppose we have a REALLY BIG compression blast - say one resulting from a fusion initiation. We get a massive compression, we can use a relatively small core and consume nearly all of it. By now, lights should be coming on. Its true the majority of the explosive power in a fusion initiation isn't from the fusion component, it's from the fission component.

In other words, a fusion device isn't really a fusion device, its a very efficient fission device. Lets do some calculations.

One estimate of the yield of the Model 1561 dropped on Hiroshima is roughly 21 kilotons. The common estimate for its efficiency was a depressing 4 percent. If we could get 100 percent efficiency we would get a yield of 21 x 100 / 4 = 525 kilotons. Doesn't that figure look impressive? And familiar?

In fact we can go further. The fusion initiation is such a spectacular and efficient way of compressing the core, we can over-engineer the device. We can layer extra fissile around the device in such a way that it feeds the fission reaction - and get startling yields. This is called a fission-fusion-fission device.

IIRC (I'll have to check the figures for you) the most that the fusion component in a fusion-fission device over delivered was around 30 percent of the total yield. If we engineer the device right, the fusion yield is just enough (and no more then that) to ensure that the fissile core is completely consumed. We've never quite got there but we're trying.

Now lets take this a bit further. If we engineer our core properly so that its massively compressed, we can actually get away with a relatively small amount of fissile. And since that is the primary cause of energy release, we've made a very small clean warhead.

Another example of what I've kept saying. The nuclear world is weird; when we start to look at how it all works we end up in very different places from where we wanted to go when we started. We try to create a super-bomb by using fusion and find out that its a great way of making efficient fission devices. Oh yes, modern devices? Very high fission component in the yield, very low fusion - to the point where its arguable if modern devices are fusion weapons at all.

[phongn]

Wait a tick, I is confused.

As I was to understand it, the fission device was used to superheat the hydrogen so the atoms have enough KE to overcome coulomb repulsion. So which stage is fired first? The fission stage, or the fusion stage?

Most bombs today are Fission-Fusion-Fission devices.

Are you sure about that? Stuart noted that you could use a FFF warhead to get huge yields, but not that it was actually done. Various web sources indicate that even the 9MT B53 was "merely" a fission-fusion device.

[Zoink]

Would a sufficiently large mass of weapon-grade material reach critical mass on its own?