All of the gravity shield things turn out to be bogus AFAIK. Like the people didn't account for the outgassing from their cyrogenic fluids and other such sloppiness. Or it was announced from a guy who refused to show his apparatus to anybody until they funded his work for a million bucks because he was "afraid they would steal it".

The biggest clue it didn't pan out is that if it were real we would be using it now.