The Swords of Armageddon was only ever available digitally (first on CD-ROM, then as download). Hansen's widow used to sell it after his death but she is no longer responding to sales requests. Or at least mine was ignored early this year. You can find it on Library Genesis.

U.S. Nuclear Weapons: The Secret History is sadly missing from LibGen, but it appears to be available as a digital checkout from the Internet Archive. It's a good companion book to Swords because it went through a professional editing-publishing cycle. Swords is a lot longer and rawer, with a higher ratio of text to illustrations.