Possibly also they do have some real advanced program that actually is working and they want a smokescreen up to explain it. Maybe some new stealth craft or propulsion or guidance system that is a normal leap forward. Maybe a drone with especially advanced ai guidance systems that allows for more maneuverability. Something the Chinese could copy if they knew how it worked. Or the reverse — that we have discovered some system the Chinese created and are trying to copy it and want them to think we have gotten it wrong.
The first seems quite reasonable. The very public smokescreen would be to control the narrative. Every time someone reported seeing such a thing, the public could be told it is probably just the US working on UFO technology. Certainly I believe the average person without a science degree will not see just how impossible this patent is.
What's really odd is the reply of the patent examiner. It's almost like they are asking, "so just to make sure I understand you, this is quite impossible, right?". The military replied, "yeah of course it is, it would require more energy than could be produced by all the power stations on earth, even if the physics were sound. If it makes you feel better, we could add that we are doing this on battery power".
The general public doesn't seem concerned enough to need a smokescreen, and I wouldn't necessarily consider this "very public." Most people either already believe it's nonsense, or probably secret classified terrestrial craft, or aliens regardless of the official position. The military could probably get away with simply ignoring any rumors and sightings and letting them disappear into the noise of pop culture.
