Following the 1994 Shoemaker-Levy 9 comet impacts with Jupiter, Edward Teller proposed, to a collective of U.S. and Russian ex-Cold War weapons designers in a 1995 planetary defense workshop meeting at Lawrence Livermore National Laboratory (LLNL), that they collaborate to design a one-gigaton nuclear explosive device, which would be equivalent to the kinetic energy of a asteroid. The theoretical one-gigaton device would weigh about 25–30 tons, light enough to be lifted on the Energia rocket. It could be used to instantaneously vaporize a asteroid, divert the paths of extinction event class asteroids (greater than in diameter) within short notice of a few months. With one year of notice, and at an interception location no closer than Jupiter, it could also deal with the even rarer short period comets that can come out of the Kuiper belt and transit past Earth orbit within two years. For comets of this class, with a maximum estimated diameter of , Chiron served as the hypothetical threat.