Grant David Callin (born 1941) is part of the hard science fiction stream of authors. He sometimes goes by the pseudonym Flash Richardson. Callin graduated from the Air Force Academy in 1963, and retired from the service in 1984. He holds a bachelor's degree in basic sciences, and advanced degrees in space physics, physiology and biophysics. An amateur astronomer, he built his own -inch () telescope and does some astrophotography.