 With special designs of the nuclear explosive Ted Taylor estimated that fission product fallout could be reduced tenfold, or even to zero, if a pure fusion explosive could be constructed instead.A 100% pure fusion explosive has yet to be successfully developed, according to declassified US government documents, although relatively clean PNEs (Peaceful nuclear explosions) were tested for canal excavation by the Soviet Union in the 1970s with 98% fusion yield in the "Taiga" test's 15 kiloton devices, 0.3 kilotons fission, which excavated part of the proposed Pechora–Kama Canal.The vehicle's propulsion system and its test program would violate the Partial Test Ban Treaty of 1963, as currently written, which prohibits all nuclear detonations except those conducted underground as an attempt to slow the arms race and to limit the amount of radiation in the atmosphere caused by nuclear detonations.