And in the Honorverse they control gravity sufficiently for it to initiate fusion directly on its own.Loren Pechtel wrote:Nope. Chemical explosives aren't a drop in the bucket compared to what's needed. Chemical explosives are simply used to very quickly convert a subcritical mass of fissionable material to a highly supercritical mass (by altering it's shape.) In a standard real-world hydrogen bomb there is a mass between the initial fission stage and the fusion stage that will effectively mean the fusion stage is untouched by the explosives. The power of the fission stage is first used to heat light material wrapped around the fusion stage. Expanding outward is limited by a wrapping of heavy material (note that this is purely a matter of inertia, strength is irrelevant), much of the energy goes inward compressing the fusion stage. The mass between the fission and fusion stages acts as a slight delay before compressing it in the other direction. Even all that fury isn't enough to set it off, though--that is accomplished by a plutonium rod in the center of the fusion stage, when it's compressed lengthwise it goes off in a second fission explosion, that actually ignites the fusion stage.
(And there is a limit on how much lithium deutride you can compress with the power of the fission bomb, if you want an h-bomb that's even bigger you use the whole thing to provide the energy to compress an even bigger bomb. You can also put another fusion stage on the opposite side of the original fission bomb.)
Their nuclear missiles and laser heads have no fission stage. They use grav pinch implosion to ultra-compress the fuel to the point of fusion (rather than using the x-rays of a fission explosion to excite the fuel to the point of fusion; as with our modern day fusion bombs). Of course a warhead's fusion reaction is not self-sustaining, and doesn't even try to be, it simply uses sacrificial gravity generators to trigger the fusion explosion - and then yet more gravity to shape the resulting blast.
But we know that these pure-fusion warheads existed long before missiles had micro-fusion reactors of their own. So that's evidence that stored power is sufficient to jump-start grav induced fusion.
So I've no reason to think that a full up starship's reactors would be capable of the same gravitational self-start capability. The difference between them and a fusion bomb is less in how they start and more in the additional fields that keep the resulting fusion contained.
It seems most likely that it is only the micro-fusion plants used in Ghost Rider drones and Mk23s that lack the self-start capability.