That still involves getting it through security, though. What’s the benefit of that over the unsecured parking lot?
Fun fact: It is possible, with enough shielding, to mask that radiation… but that shielding, itself, can be detected. One technique used is to pass your suspected payload over the top of a radiation detector, and look for a decrease in the naturally-occurring cosmic ray flux. As I understand it, such detectors are installed at most of the major land crossings into the US, and the Coast Guard has ships that can do it, also.
Very true, not to mention any shielding that would stop radiation from a nuclear device is going to also be opaque to X-rays. As soon as it passes through an X-ray machine TSA is going to know something suspicious is going on. You’d want to get a conventional bomb into the terminal and as close to your target as possible, but when we’re talking half-megaton yields you could park your bomb in long-term parking and still be sure to wipe the airport as well as the surrounding neighborhoods off the face of the earth.
Rumor control had it back in the day that the Soviets had smuggled several “suitcase nukes” into the US, mostly via diplomatic pouch. The latter refers, I guess, not so much as an actual pouch as such but containers or cargo or that are immune from normal inspection and customs. So it is at least conceivable.
Sure, some will go for the suitcase but pound for pound, the W-56 delivers the best explosive potential. Come into my office and we’ll discuss payment options.
The rolling suitcase wasn’t invented until 1970 so it is important to establish the decade of technology constraints. It is odd that it took almost 100 years after the invention of the airplane, and 25 years after the invention of the atomic bomb before anyone thought of combining a box with a handle and man’s first advanced technology to create the rolling suitcase.
IIRC there is a minimum size of uranium or plutonium to make a nuclear bomb go boom (critical mass). You just cannot get arbitrarily small with them and expect them to work (not counting dirty bombs here which is not a nuclear explosion).
So, the smallest possible “suitcase” bomb is going to be kinda big and heavy. You could put one in a car but you won’t be casually carrying it through an airport or anywhere else. It’ll still be somewhat large (big suitcase…it’s not just the uranium/plutonium but all the other stuff too) and heavier than any human could carry easily for more than a fairly short distance…and even then it would be awkward to carry.
Depends what you mean by big and heavy. Even a bare critical mass of plutonium weighs less than 25 lbs. We could be talking about a 50 lb suitcase nuke, for the sake of argument. However, even a kiloton-range fusion-boosted suitcase nuke is not a “doomsday device”, more like a tactical nuclear weapon.
The W-82 was supposed to be used in a 2kt artillery shell, not the W80. If you just want a suitcase nuke, besides lowering the calibre you can also do away with the rocket motor, nose cone, etc., and some of the sophisticated additional features.
I vaguely remember that the suitcase bombs didn’t contain a critical mass of fissile material. The trick being that what we consider a critical mass it at normal densities. The device (like any other) explosively compresses the material and hits it with a well timed shot of neutrons - The fissile material stays at high enough density for long enough to get a goodly sized bang. Enough to level a few city blocks, which seemed to be the intent.
The reality of this is well above my pay grade, but does sound plausible.
Is that a theoretical minimum or a practical minimum?
In other words, if someone wants to make a reliable small nuke can they get away with theoretical minimums?
Not to mention you then need other stuff like explosives and other bits to make it all work which add to the weight and size.
Can someone cram all that into a large suitcase? Maybe, I am no expert on this. I think it would still be difficult for a single person to carry around.
The 10kg figure is for a bare, unreflected sphere of plutonium-239 at normal density. Note that you need a bit more than exactly one critical mass to obtain a significant explosive yield. Now, as @Francis_Vaughan says, the critical mass can be reduced by adding a thin reflector and increasing the density via explosive compression; on the other hand, extra components themselves weigh something or at least take up space.
The aforementioned W-82/XM-785 was a 155mm shell that weighed 95 lb (the entire round), but Wikipedia quotes the late Ted Taylor as claiming that a 105mm, 42-lb shell is theoretically possible.
If you use uranium or plutonium. In principle, you could use some other isotope with a lower critical mass. Heinlein’s Starship Troopers included nuclear hand grenades, made using (IIRC) californium. Of course, the “hands” that were throwing those grenades were also significantly cybernetically enhanced.
Sophisticated extraneous stuff like large, easy-to-read red digital timers. (not actually required - strictly movie stuff??, I’m struggling to remember the timers on the backpack nuke - I think they were clockwork dials).
None of the nuclear pits are a critical mass until squished (technical term) by surrounding explosives into a small size/density.
It’s the fusion portion that’s going to up the weight considerably if you’re going beyond tritium gas boosting.
No kidding. The 155mm projectiles were storage/maintenance limited because of interactions.
The W80 got mentioned because a prior poster brought it up. And, unlike the W82, it’s a thermonuclear (fusion) warhead, in keeping with the OP of this thread. The original post stipulated the existence of person-portable fission weapons, like the SADM, and explicitly asked to extend the idea to fusion weapons.
Given this condition, I think the W80 or its equivalent may be as small as it gets. The Teller-Ulam design requires a lot of very dense metal for inertial confinement of the energy and matter products of the fission stage in order to channel all that energy into heating and compressing the fusion stage, and allowing the device to hold together long enough to do it. There’s probably a great deal more natural or depleted 238U in the tampers and reflectors than there is any fissionable isotope in the overall design. And that raises your minimum practical weight a lot.
My interpretation of the OP is actually not so much whether it is possible to make an absolutely minimal suitcase or briefcase nuke—we know that it is—but whether it be feasible, without needing too much sci-fi technology, to get, let’s say 200 kt or more. Comparing warheads that are publicly known to exist, a priori it does seem we are at best in heavy backpack territory (though, as others have pointed out, if it’s a megaton, does it really matter whether you set it off in the terminal itself or outside in the airport parking lot?) but ISTM there are some calculations to make (not sure if we should, though…) to have an idea of what the real limits look like.
