Nuclear Weapons - Uranium Enrichment

As stated in the previous post, the Manhattan Project took a two-pronged approach to accumulating enough fissile material to build the first bomb: Uranium Enrichment and Plutonium Production.

We talked about Plutonium Production in that post.  This post is about Uranium Enrichment - increasing the isotope fraction of U-235 from naturally occuring Uranium, which is mostly U-238.