The TR-3B Black Manta: What is it Really?

The TR-3B, or Black Manta, or Astra is one of the most fascinating potentially top secret aircraft ever created by the United States military. The big reason for this is that this craft is supposed to use anti-gravity technology. This technology is discussed a lot in this book. Also, what other evidence is there for the existence of this craft? There are lots of unknowns here but there are also enough pictures of this aircraft that you can't just discount sightings as being something else w...