Nation: Busload of Megatons

THE standard ballistic missile carries only one nuclear warhead. That has long seemed inefficient to Pentagon planners, considering the huge cost of missiles and the space required to store them. In the early 1960s, they developed the first improvement: a multiple warhead known as MRV (for Multiple Re-entry Vehicle). It is a relatively crude device that drops unguided from missiles in clusters of three warheads. Some MRVs have been placed on presently operational Polaris missiles. A further and major refinement is MIRV (Multiple Independently Targetable Re-entry Vehicle), which is similar to MRV but...

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