I am kind of a military buff myself. I must say that he does not seem to have really gotten it right.
He wrote:
Other designs, while seemingly even more fanciful, did in fact exist, in either prototype form or completed (and perfectly sound) blueprints. Aircraft included the Horten Ho-229 jet powered flying wing, the Mach 2.2 Lippisch P13a delta winged ramjet-powered fighter, a high altitude spyplane similar to the later American U-2 called the DFS-228, even a variable geometry swing-wing jet, the Messerschmitt P.1101, which became the precursor to the later American Bell X-5. They also had designs for a number of vertical takeoff and landing jets.
The Nazis also aggressively pursued their Amerika Bomber program, hoping to create a system with the range to bomb the United States from Germany. These included variants of the Arado E.555 jet powered flying wing, and even a suborbital spaceplane called the Silbervogel which went as far as a glide test mockup. There were many, many other candidates for Amerika Bombers as well.
None of these were ether blueprints or prototypes but instead "drawing board projects." It might be five or more years before any would likely be operational.
Also,
On land, the Nazis had plans for a pair of staggeringly gigantic tanks, the Landkreuzer P.1000 Ratte and P.1500 Monster, crewed with over 40 and 100 men respectively. They would have fired the largest artillery projectiles ever designed, the 800mm railroad gun.
Just about every military historian I have ever talked to has argued that they are completely impractical. There is a joke that the engineers kept working on them and promising so they might not get sent to the Russian front.
As well
At sea, the Nazis planned to equip a new type of U-Boat to fire their V-2 missiles into the United States, called the Rocket U-Boat. Three were ordered, and one was actually built, thought its testing was not completed before the war's end. And what would it have carried?
Everything I have ever read has indicated that it would not really have worked. Trying to target a missile from a moving small "vessel" would be impossible.
