An interesting mindgame, I hope. I'm wondering if it could be possible to build a "machine" for creating even higher densities than that of a smaller star. For example one could take a 491 m radius massive iron globe. It doesn't matter how to build it. You could surround it with a sphere of hydrogen detonators that would vapourice the outer surface as fast that you get a typical 1e15 Pa of ablation pressure. The spherical shock wave of the imploding surface would travel with the speed of sound of iron (4910 m/s) in 0.1 s to the center of the globe where it would amplify geometrically with the factor (491/0.1)^2 = 24.1e6 in a 10cm radius sphere. Nuclear fusion could not occur, because the whole globe is of iron. The shock wave would be reflected in the center and travel back to the surface, where it is partly reflected due to phase transition. Normally the outer layer of the globe would now explode, but.. After ca. 0.2 s a new spherical wave of staggered nuclear fusion explosions would be exactly triggered (considering the loss of material due to ablation) that the new shock wave superimposes the old. This new ablation induced pressure impulse should also hinder the outer material of the iron sphere to explode. It should be theoretical possible to increase the shock wave pressure from blast to blast. Let's say 50% of the shock wave would be reflected at the surface. Then it would be still possible to increase the pressure (neglecting the flattening of the shock wave peak with time) by a factor of 1.5^100 = 4e17 with 100 spherical blasts from outside. This means after 100 blasts or 20 seconds one would have theoretically a pressure in the 20 cm diameter central region of the iron globe of 1e15 * 24.1e6 * 4e17 = 9.64e39 Pa. That seems to be enough for a neutron star. What do You think? Where is the error in reasening? Is it theoretically possible to build an artificial 20cm diameter neutron star in this way?