Worlds for the Taking — Kenneth Bulmer

Terran Corps scattered their ships outward into the glittering galaxies. Solterra's prime objective: orbital reconstruction of the far-flung planets. They had tightened up Solterra's galaxy and had made mankind secure against alien threats - or so Terrans believed.

As Chief Commander, Stephen Strang aggressively explored the cosmos for the glory of his beloved Earth. He could boast that he had moved more planets into orbit around Sol than any other. Strang felt smugly safe against alien "sharks" - until he discovered the vast time-bomb that was planet Vesta's core. . .