As for the H-Bomb internal combustion device, that sounds an awful lot like Freeman Dyson’s plan for nuclear spaceship propulsion. Poul Anderson wrote a story (Orion Shall Rise, I think), in which such a craft performed derring-do in the Earth’s atmosphere; the thought alone is enough to turn any less of a technophile into a honey-&-locust munching Luddite.

You might be thinking of Z-pinch machines, but those are more for igniting fusion and studying extreme environments rather than creating a long term sustainable reaction.

However… I once read about a crazy idea of detonating thermonuclear warheads in a huge underground bunker where their energy would be absorbed by giant, moving plates kicked back by the blast wave. And as you can probably imagine, that idea was abandoned about as quickly as it was brought up.

Last I heard, the fine art of nuclear fusion requires maintaining a continuous explosion, held a bit below the containment capacity of one king-hell pressure cooker. It’s rather like riding a motorcycle along the edge of a cliff: minor bruises and chagrin if you fall over on one side, but qualitatively different the other way.

Perhaps the proposed engineering has become rather more fail-safe since I read up on all this, but I’d still vote for keeping the “tame” H-bomb approach on the drawing boards until we’ve totally exhausted all the Amory Lovins approaches.

Fusion reactors can’t blow up like a nuke. In thermonuclear weapons, a fission device is used to ignite substantial quantities of deuterium and tritium very quickly and violently, with no regard for the efficiency of the reaction.

Controlled fusion reactions work on slightly different principles and lacking an ignition as powerful as another nuclear bomb, making it go boom would be rather difficult to say the least.

Yabbut there is that potentially embarrassing Ka-BOOOM!!! problem.