I think a great pre-explosion warning would be to throw particles out into space in random directions in more frequent and urgent cycles, to illustrate parts of the ship are starting to explode all over the place. Nearer to the moment where the main explosion starts, the core is spitting out fountains of particles (sparks, embers, etc.) to illustrate terminal criticality. It would be visually exciting, and as the particles become more regular, it would provide an immersive visual countdown. I am thinking if particle systems look good enough, I'll want to just stand by and watch as the ship goes up. It'll be beautiful. Poof.... Poof.... Poof, poof... Poof... Poof, Poof, Poof... Poofffffffffff, BOOM!
Plus, particle systems can be scaled back for older computers, so it'll work for a wide range of computer capabilities, with ship explosions on good computers that can handle detailed particle systems looking gorgeous.