HG Wells, apparently, had the concept of an “atomic hand grenade” which had the special property that, after it was triggered, it “would continue to explode indefinitely”.
At the moment, we seem to have the ability to excite reactive materials so that they fission at an increased rate - up to a super smolder - and the ability to make everything let go at once and release a single, extreme explosion.
Would it be possible to create a nuclear reaction that takes, for example, ~10 minutes to fully release its energy? Would it be more like an explosion or more like the world’s most extreme bonfire?
Sounds pretty much like a core meltdown. Those are known to have caused explosions as well (see Chernobyl and Fukushima).
Randall Munro has an amusing take on it in his What If? piece about the indestructible hair-dryer, where he briefly mentions H G Wells idea: Hair Dryer
Given that an explosion is “a sudden expansion of gas”, I’ll grant that it may not be meaningful to talk about an “ongoing” explosion but I think if we can maintain a wall of heat that lasts for an extended period of time while holding, for example, a bubble of flame at the perimeter and fizzle out sometime before sinking so far into the Earth that the energy release becomes strongly directional, then I would consider that to be within the realm of what Wells might have been thinking even if it’s not “indefinite”.
Wells was not the only one who thought of A bombs as a continuous process. A number of other SF writers of the pre-nuclear weapon era had similar ideas as to what would happen once you got a fission reaction started.
I’m not up to speed on high energy events like this, but it seems to me that spreading it out over minutes would greatly reduce the destructive power that you would normally get from the shockwave.
I think H.G. Wells devised this idea after talking to various physicists at the time, several of whom were familiar with the apparently miraculous energy output of radioactive materials. The rapid release of energy in a chain reaction wasn’t something that had occured to anyone - yet.
Probably the closest to his fizzling atom bomb would be a NERVA nuclear rocket, which was expected to be capable of a burn lasting 21 minutes or more.
So, basically parking a Project Pluto nuclear ramjet on the ground in the middle of a city, and turning up the output to just before structural meltdown.
There was worry at the Manhattan Project, and apparently among German physicists, that a fusion event would not stop but would continue and ignite Earth’s atmosphere. (cite) Don’t try this at home, kids.
Then I don’t see how this would be possible with anything like current technology. There have been deadly accidents involving plutonium or uranium in research and laboratory settings in which quantities of fissionable material have unexpectedly achieved a prompt-critical state that have killed (albeit maybe not right away) several people in a room before, but not with thermal heat energy as you seem to be envisioning with your “bubble of flame.” Even if you did get something like a core meltdown scenario that at least gave off a glow of molten metal, it would be the radiation, not the heat, that did the killing before the heat was even a factor.
Most of the energy from nuclear fission is from fission fragments, which repel one another at at something like 1/3rd light speed.
To get the maximum possible energy, we want to get as as many atoms as possible to fission before the device is no longer in an optimal configuration to cause new reactions. This kind of device, by constraints, is more or less going to be a bomb.
A device designed to emit bomb-like amounts of energy… well, at that point we’re talking about one of two things… either a reactor undergoing some sort of controlled (or uncontrolled) meltdown, or a large amount of gas becoming a star.
The answer is one of:
1: No, if we’re talking about a bomb, the device releases its energy almost instantaneously.
2: Yes, if we’re talking about a very specially designed nuclear reactor with special control rods, neutron poisons, and moderation materials, then you could engineer a fission reactor meltdown intended to emit energy for some extended period of time.
Much depends here on the definition of “hand grenade”. I feel like it could be done with something on the order of a 18lb bowling ball, but I would not volunteer to be first in line for the test throw.
But such a thing would not “explode” over the course of ten minutes or create a lasting ball of fire, which is why I did not seek to explore this option. And as the reactor would be undergoing meltdown, it would not hold the necessary geometry to maintain criticality for long.
There would be ways to create a cycling emitter of intense radiation by, say, allowing a neutron moderator to flash to steam, then cool and collect, then begin moderating neutrons again, but that is right out because, again, there is no explosion, no ball of fire, just intense and deadly radiation surrounding the object.
The trick is to keep your nuclear reaction bound; the problem with bombs (and supercritical reactor configurations) is that they have a tendency to self-disassemble. For an example of how to do it right, and what it looks like, consider the sun.
Do not be discouraged, though; you can readily incinerate people closer to home using techniques such as the flame fougasse, napalm, thermobaric explosive weapons, and white phosphorus.
As others have said, you can either make a bomb by creating an exponentially increasing rate of nuclear reactions in the material or a controlled reaction where the rate reaches a certain point and then stays there for a time.
There is no law of physics that says you can’t have a controlled nuclear device that burns up over a period of 10 minutes, as opposed to e.g, a few years in a commercial power plant.
It is a mere engineering problem to find some way to dissipate the rather large power density in such a way as to avoid self destruction.
Note that meltdowns like Three Mile Island or Fukushima (not Chernobyl) happened at a very low power, after the reaction was long shut down, the reason was not high power but failure of cooling.
Maybe I’m missing something, but this seems rather trivial.
You build your ‘atomic hand grenade’ with a time-delay fuse (just like regular hand grenades).
This is nothing new.
The Hiroshima bomb had about a 45 second delay before it ignited. And many of the German bombs dropped on England during the blitz had time-delay clock mechanism inside them.
Yeah, you are missing the whole point.
The idea is not to delay the explosion, but to make the explosion take a very long time. Basically “burning” instead of exploding.
Right, Wells was writing in 1914, well before much of the physics of real-world nukes was even figured out, so he was not at all clear on how such things work. Also he uses a confusing nomenclature, since to anyone either now or in his time “hand grenade” conveys the concept of an explosive, not a sustained-effect device.
What he seems to be describing sounds to me, if anything, more along the lines of an omnidirectional Death Ray, shining 360 degrees on all 3 axes until the source were exhausted.