During the quarter covered by this progress report (July 15October 15, 1972), the power requirements of a bench test heart pump were determined. Cardiac output response, peak pusher cup forces, and power efficiencies were also determined. These measurements were made in vitro. Several geometries of connectors for the heart pump were evaluated for fit in dead calves to determine a practical configuration. Two models of the nuclear engine were implanted in calves to evaluate the chronic effects of engine weight and size. (auth)