Dark Star UAV?

Until the other day, when I saw a program about UAV’s on the History channel, I thought the Dark Star was a fictious aircraft.
I read ‘The Bear and the Dragon’ which talked about this ‘Super’ aircraft.
Does anyone have any info on this aircraft? Range, payload etc

It must have been prity good if Lockheed Skunk works and Boeing Jointly produced it, so why did the US cancel it?

again, sorry for asking Questions all the time.
Baz