Silent slow flying triangular aircraft.We saw a triangular shaped aircraft. It had three lights on each side of the leading edge of the aircraft. I think the altitude was less than 300 feet. The aircraft seemed to be 100 to 150 feet across. It was flying slow, probably less than 100 miles per hour. It was completely silent. We were camping on Marsh Miller lake and the aircraft was heading north. The shape was very distinct in the star filled night sky. My friend and I we're extremely interested in it and watched it fly out of sight. I have seen many aircraft while serving in the US Air Force but nothing like this. It was definitely an experimental silent propulsion aircraft.