Check the projects like SHIVA STAR , and under that project , project M.A.R.A.U.D.E.R. - the examples like that is what was short mentioned in public , and then dissapeared out from public eye in early 90s .  In other words , we have TWO types of "black projects" - acknowledged and unacknowledged , acknowledged become public at one point , unacknowledged never ... or not yet , until supression is gone .  Rocket and jet technology ... obsolete .