His two - volume work entitled Space Flight is probably the most complete and surely the most useful introduction to this complex subject ever written .
Ehricke was an accomplished practitioner in the field of astrodynamics and its applications .
Ehricke 's two - volume work entitled Space Flight is probably the most complete and surely the most useful introduction to this complex subject ever written .
Ehricke was an accomplished practitioner in the field of astrodynamics and its applications .