Oh, that thing. It was a lemon. A cool looking lemon, but a lemon.[1]

There are three videos:

#1: Classified SECRET. It hasn't flown yet, but it's going to be really great. See this cool mockup!

#2: Classified OFFICIAL USE ONLY. It flies! Well, hovers about 1m off the ground in ground effect. Wobbles too much. But with our elaborate testing program, a NASA wind tunnel, and maybe with more powerful engines and active stabilization, it can work!

#3: UNCLASSIFIED. Well, here we are flying this thing around the back lot at NASA Ames as a hovercraft. Not too useful, but cool looking.

It's a nice video history of a failed project.

Meantime, the Army was also funding the UH-1, the "Huey" helicopter, which started flying around the same time and was far more useful. So the Army killed off the disc project and ordered a few thousand Hueys. The USAF, meanwhile, had figured out that swept back wings worked in high-speed flight, and didn't need to fool with discs.

[1] https://www.fourmilab.ch/documents/army_saucer/

Holy cow, the Hiller Flying Platform rocks!

If you're in Silicon Valley, there's one at the Hiller Aviation Museum. They have a good collection of strange VTOL craft.