 Delivery by an intercontinental ballistic missile would have required a much stronger missile (the Proton started its development as that delivery system).It has been estimated that detonating the original 100 Mt design would have released fallout amounting to about 26% of all fallout emitted since the invention of nuclear weapons.It was decided that a full 100 Mt detonation would create a nuclear fallout that was unacceptable in terms of pollution from a single test, as well as a near certainty that the release plane and crew would be destroyed before it could escape the blast radius.