Charles Sheffield (1935-2002) received a PhD in theoretical physics from Cambridge, was a Fellow of the British Interplanetary Society and the American Astronautical Society and became an award-winning science fiction author.  He was a popular speaker at conventions and was generally considered a “Renaissance Man” who could converse engagingly on just about any subject, from poetry and music to mathematical conundrums.  He was married to the science fiction writer Nancy Kress.