An explosive system and corresponding method employ a number of explosive portions, each of sub-critical dimensions so that initiation of the portion would result in incomplete detonation. A selectively-deployable spacer arrangement or deployment mechanism is deployed between a storage state in which gaps or misalignments are maintained between the explosive portions so that the explosive system remains undetonatable, and a detonable state in which the portions are brought together sufficiently to function as a combined explosive charge having effective dimensions larger than critical dimensions, rendering the explosive system detonatable.