Bright violet cigar shaped Berthold North Dakota

During a fishing trip at Lake Sakakawea on the Berthold in res. we saw a very large cigar shaped object that appeared to the west.
It slowly flew almost a hover past us on a southeast course not making a sound.
It appeared to be 800 -1000 feet in the air and was a fuzzy violet color with smudges of black grey areas on it. It had to be as big as a KC135 It was bright enough to reflect of off the lake. 
At one point it stopped and sort of bounced up and down 50 feet.  It then continued on at a sharp upward flight angle until it no longer could be see at a incredible high speed 
I was in my late teens and an USAF brat at the time and have seen many aircraft and this was moving way faster than any military fighter and no sound.