The Americans initially intended to pair Skybolt with the W47 warhead, an innovative light-weight design from the Lawrence Radiation Laboratory developed for Polaris. The British wanted to use Red Snow, partly for safety reasons and partly because it was not certain that the advanced M47 design would be made available without strings attached. The technical problem was that Red Snow was heavier, and therefore the range of the Skybolt would be reduced from . A megaton design known as RE.179 based on the W49 warhead used in American ICBMs was developed for Skybolt.