From BIG to small.....

[TheSleeper]

I just want to know why old heavy nukes that were detonated in Japan were transpoted by huge planes through the free falling method. But nowadays, we can compact them into a missile and can be brought by sub/movable trucks or even in a suitcase yet the damage is scaled up........

Isn't true that the heavier the nuke, the larger the damage it will impose ?

 

[Matthias99]

Originally posted by: TheSleeper
I just want to know why old heavy nukes that were detonated in Japan were transpoted by huge planes through the free falling method. But nowadays, we can compact them into a missile and can be brought by sub/movable trucks or even in a suitcase yet the damage is scaled up........

Isn't true that the heavier the nuke, the larger the damage it will impose ?

Well, the more material undergoes fission (or fusion, in the case of hydrogen weapons, but AFAIK those have not been made "small" yet), the higher the yield of the weapon in kilo/megatons.

There are two opposing factors. First, improvements in technology have greatly reduced the size of the "stuff" that goes around the actual fission material. Better explosives and computerized timers have made nuclear weapons much smaller, lighter, and more reliable. At the same time, during the cold war the focus was largely on making weapons with a higher and higher yield (so as to better blow the stuffing out of those damn commies!)

However, since the end of the cold war, the emphasis has been more on getting rid of the REALLY huge nukes and developing more 'tactical' nuclear weapons that can be used for pinpoint strikes.

So, basically, the yield/pound and yield/cubic foot has gone WAY up (which makes a bomb with the same yield much smaller and lighter), but it's also possible today to make weapons with a yield much *lower* than the first atomic bombs. A multi-megaton H-bomb will be very large indeed, but a very small bomb with a yield of a few kilotons might fit in a suitcase.

 

[Gibsons]

Originally posted by: Matthias99

Originally posted by: TheSleeper
I just want to know why old heavy nukes that were detonated in Japan were transpoted by huge planes through the free falling method. But nowadays, we can compact them into a missile and can be brought by sub/movable trucks or even in a suitcase yet the damage is scaled up........

Isn't true that the heavier the nuke, the larger the damage it will impose ?

Well, the more material undergoes fission (or fusion, in the case of hydrogen weapons, but AFAIK those have not been made "small" yet), the higher the yield of the weapon in kilo/megatons.

There are two opposing factors. First, improvements in technology have greatly reduced the size of the "stuff" that goes around the actual fission material. Better explosives and computerized timers have made nuclear weapons much smaller, lighter, and more reliable. At the same time, during the cold war the focus was largely on making weapons with a higher and higher yield (so as to better blow the stuffing out of those damn commies!)

However, since the end of the cold war, the emphasis has been more on getting rid of the REALLY huge nukes and developing more 'tactical' nuclear weapons that can be used for pinpoint strikes.

So, basically, the yield/pound and yield/cubic foot has gone WAY up (which makes a bomb with the same yield much smaller and lighter), but it's also possible today to make weapons with a yield much *lower* than the first atomic bombs. A multi-megaton H-bomb will be very large indeed, but a very small bomb with a yield of a few kilotons might fit in a suitcase.

What Matthias said... plus..

Strategy wise, we've moved to smaller bombs as the guidance systems got better. They've spent a lot of time figuring out what the accuaracy of an ICBM is and how big of a bomb you need to be sure you take out the target. With very accurate guidance, you can use much smaller and much cheaper weapons.

Also, we've got a lot of data on bombs now, when the first ones were built they would overbuild to be sure they would work. We know enough now to cut things down to the minimum. I'd guess better electronics might help in making the implosion more closer to perfectly symmetrical too, which might mean you need a little less material.

I can't find the link right now (I'll look again later) but I saw one page saying that one important way the US has been able to shrink nukes is by making the first stage nuke in an ovoid shape rather than spherical. I think this just lets it fit into a conical warhead better, but I can't be sure. In any case, a modern two stage weapon with a ~500 kiloton yield can fit inside a mirv warhead that's only about 3 feet high.

Edit: link

 

[Calin]

The uranium bomb that leveled Hiroshima was the first of its type. No previous real scale tests, no nothing. The plutonium bomb used against Nagasaki was the second of its series, and the test before was made with a smaller bomb.
As such, they really had no place for failure. With the technology of those times, any of the bombs could have been made something like two thirds the size (and with great risks of malfunctioning).
The current evolution? Using much more precise manufacturing and ignition can reduce the needed mass of uranium/plutonium just a bit over the critical mass. Better materials for bomb components allow for lighter bombs. Better first stage explosive reduce the mass even more (by reducing the needed uranium/plutonium mass and by reductions in their own mass). And another thing, the first bombs might had electricity from something like a car battery, while the current ones use something more like 2 AA batteries.