Nuclear Fusion Warheads?

markusschaber wrote:Hi,

just a thought: Warheads traditionally use a nuclear bomb to pump the lasers. But while "normal" missiles power their drives using supercapacitors, RMN missiles use fusion reactors, which can also produce a nice explosion.

So could the fusion reactor be used to pump the laser rods, removing the need for the bomb?

In a word, no.

Because a reactor is not a bomb. It can be made to explode, eventually. But to be a trigger, a nuclear bomb needs to be able to explode on demand, not eventually. It is all about timing. And a nuclear reactor cannot go from stable to exploding at a moments notice. Hydrogen bombs are very complicated designs relying on symmetry and timing.

It's like a ballistics engineer who needs to precisely set up the amount of explosives and their precise positions to bring a building down in the midst of other buildings without collateral damage. It would be rather difficult to impossible to “control” the timing and the forces of a nuclear reactor. The reactor would simply produce an inefficient explosion. And bombs, in this and every application, need to be very efficient.

penny wrote:Because a reactor is not a bomb. It can be made to explode, eventually. But to be a trigger, a nuclear bomb needs to be able to explode on demand, not eventually. It is all about timing. And a nuclear reactor cannot go from stable to exploding at a moments notice. Hydrogen bombs are very complicated designs relying on symmetry and timing.

I agree that bombs are much cleaner, simpler and more powerful.

Saying that a reactor can be made to explode "eventually" would be comforting, if true. But how do we know that it is true? We know that human reactions are not good enough, so that computers are needed to monitor any reactor. So could "eventually" be a matter of microseconds (at most)?

tlb wrote:

penny wrote:Because a reactor is not a bomb. It can be made to explode, eventually. But to be a trigger, a nuclear bomb needs to be able to explode on demand, not eventually. It is all about timing. And a nuclear reactor cannot go from stable to exploding at a moments notice. Hydrogen bombs are very complicated designs relying on symmetry and timing.

I agree that bombs are much cleaner, simpler and more powerful.

Saying that a reactor can be made to explode "eventually" would be comforting, if true. But how do we know that it is true? We know that human reactions are not good enough, so that computers are needed to monitor any reactor. So could "eventually" be a matter of microseconds (at most)?

In this kind of application of being a trigger, being microseconds too late or too soon would destroy the application. Certainly in a H-bomb. But there is no need to overthink it. One is a reactor. One is a bomb. A reactor is developed not to explode easily. An explosion is not what is sought. A smooth reaction is sought. Hence, a reactor. If you want something to explode easily and at a moments notice then make a bomb.

But you can't go from a relatively stable and controlled reactor to an instant "controlled" bomb.

tlb wrote:

penny wrote:Because a reactor is not a bomb. It can be made to explode, eventually. But to be a trigger, a nuclear bomb needs to be able to explode on demand, not eventually. It is all about timing. And a nuclear reactor cannot go from stable to exploding at a moments notice. Hydrogen bombs are very complicated designs relying on symmetry and timing.

I agree that bombs are much cleaner, simpler and more powerful.

Saying that a reactor can be made to explode "eventually" would be comforting, if true. But how do we know that it is true? We know that human reactions are not good enough, so that computers are needed to monitor any reactor. So could "eventually" be a matter of microseconds (at most)?

Probably not. Not unless you wanted a pretty weak explosion.
A fusion reactor is carrying along at a steady state of fusion reaction -- meaning the pressure and fuel are carefully balanced to ensure that the rate of fusion events is steady (on average each fusion event causes just one additional fusion event to occur). In contrast a fusion bomb requires sufficient fuel and density for a runaway cascade of fusion reactions; each fusion event triggering at least two more.

Now an Honorverse fusion reactor holds a highly compressed and very hot plasma; restrained primarily by gravity and magnetic confinement. If those fields go down, or get overwhelmed, then that very hot plasma will rapidly vent and wreck anything around (including large parts of ships should a ship reactor fail while inside it). But that won't be a fusion explosion, and in fact the moment the plasma starts expanding the conditions necessary to sustain fusion are lost. The plasma is rapidly becoming cooler and less dense -- which means hydrogen is no longer hitting itself hard enough to fuse. This not only means it's far weaker than a fusion bomb using the same amount of fuel, but also that as fusion stops production of gamma rays stop -- the gamma rays a laserhead relies of to excite the lasing rods.

It's possible that you might be able to turn off those containment fields in a matter of microseconds (though I'd bet on enough "inertia" in their generators that they'd last for milliseconds if not entire seconds; even if power was cut. But that doesn't get you the thermonuclear explosion you need.

You could override the regulators and shove more fuel into the reactor -- which would increase temperature and pressure to the point the containment failed. But that takes time, probably a couple of minutes, and it's still very likely to cause containment failure before building up to the point it can cause a truly runaway fusion reaction and give you a thermonuclear explosion.

You might be able to radically increase the grav compression -- that'd seem to be the best way to potentially get a thermonuclear explosion out of a fusion reactor. If you can force it to produce a similar grav pinch effect as the warhead uses you might be able to squeeze it into a supercritical state before the containment fails. (But that's seem to require a reactor whose containment was designed to specifically do that; of which had an extra grav pinch generator added to it. And even then I suspect trying to hyper-compress plasma that's already fusing is going to be less effective than compressing it before initiating fusion; that in the already fusing plasma you'd wouldn't be able to generate as great a compression before it all came apart)

tlb wrote:Saying that a reactor can be made to explode "eventually" would be comforting, if true. But how do we know that it is true? We know that human reactions are not good enough, so that computers are needed to monitor any reactor. So could "eventually" be a matter of microseconds (at most)?

Jonathan_S wrote:Probably not. Not unless you wanted a pretty weak explosion.
A fusion reactor is carrying along at a steady state of fusion reaction -- meaning the pressure and fuel are carefully balanced to ensure that the rate of fusion events is steady (on average each fusion event causes just one additional fusion event to occur). In contrast a fusion bomb requires sufficient fuel and density for a runaway cascade of fusion reactions; each fusion event triggering at least two more.

I never expected to use a reactor to power the x-ray rods of the warhead. I merely wondered if it was that hard to get any sort of explosion, beyond the release of the hot plasma. Even a "pretty weak explosion" is enough to satisfy my curiosity.

tlb wrote:I never expected to use a reactor to power the x-ray rods of the warhead. I merely wondered if it was that hard to get any sort of explosion, beyond the release of the hot plasma. Even a "pretty weak explosion" is enough to satisfy my curiosity.

Turning off the containment fields would be like a pipe bomb on steroids -- it's not a nuclear explosion but it'd still explode by pretty much anybody's definition (even if technically it's just a, very, very, rapid release of hot plasma)

Getting an nuclear explosion would be much harder (unless the grav containment could be convinced to briefly act like a weapons grade grav pinch)

tlb wrote:I never expected to use a reactor to power the x-ray rods of the warhead. I merely wondered if it was that hard to get any sort of explosion, beyond the release of the hot plasma. Even a "pretty weak explosion" is enough to satisfy my curiosity.

Jonathan_S wrote:Turning off the containment fields would be like a pipe bomb on steroids -- it's not a nuclear explosion but it'd still explode by pretty much anybody's definition (even if technically it's just a, very, very, rapid release of hot plasma)

Getting an nuclear explosion would be much harder (unless the grav containment could be convinced to briefly act like a weapons grade grav pinch)

Well there is the extra gravity pinch effect from the rings added to focus the explosion on the rods.

Jonathan_S wrote:

tlb wrote:I never expected to use a reactor to power the x-ray rods of the warhead. I merely wondered if it was that hard to get any sort of explosion, beyond the release of the hot plasma. Even a "pretty weak explosion" is enough to satisfy my curiosity.

Turning off the containment fields would be like a pipe bomb on steroids -- it's not a nuclear explosion but it'd still explode by pretty much anybody's definition (even if technically it's just a, very, very, rapid release of hot plasma)

Getting an nuclear explosion would be much harder (unless the grav containment could be convinced to briefly act like a weapons grade grav pinch)

Anything you can do would not yield an explosion that would satisfy the necessary parameters of the application. It would be highly unreliable. And probably not as efficient. Even in the HV, reactors are built with safety features installed. If one defeats the safety features of a reactor one has made an unstable bomb. What you would get would act like the old unreliable cheap fireworks way back when I was a kid. Very unreliable and more dangerous than you bargained for.

A trigger needs to be as sensitive as a "hair trigger." I think if containment is lost there'd be time to eject the reactor. That's way too much time for the application. Next time there'd be less than enough time to eject the reactor.

A reactor is simply not a bomb. And thank God! I live way too close to one.

In 1961, a nuke was inadvertently dropped on the city of Goldsboro, NC. A broken arrow I suppose. It did not explode because of a less than five dollar safety switch at the time. I lived way too close to Goldsboro and I was a classmate of one of the daughters of one of the survivors of the crash.

A reactor is not a bomb is not a reactor.

Don't take a knife to a gunfight. And don't take a reactor to a bomb fight. You would be at a worse disadvantage than muzzle loaded rifles were against pistols. You wouldn't have the necessary time.


https://en.m.wikipedia.org/wiki/1961_Go ... B-52_crash