"In March [2006] the nuclear crisis involving Iran became more acute, as satellite photos showed what looked to be an excavation for a test shot. That made it appear that Iran was on the verge of having a bomb, rather than, as had been imagined, still some years away from having one. To the extent that the Iranians plan on using enriched uranium rather than plutonium, they can produce a very simple weapon much as the United States did in 1945: a gun in which enough uranium is fired at another chunk of uranium to produce a critical mass. Such a device is so simple that it needs no test; the first U.S. uranium bomb "Little Boy," was simply dropped on Hiroshima. The drawback is that such a bomb needs a great deal of highly-enriched uranium, and that it is quite massive. It is anything but a missile warhead. Presumably, if this is what the Iranians are doing, they are interested in a test essentially as an announcement that they are a nuclear power. Of course, the hole may also be another move in the war of nerves between the Iranians and those in the West trying to dissuade them from building a bomb."