The Saturn I booster which is powered by a cluster of eight rocket engines has been successfully flown on four successive flights. The early success of this large launch vehicle is a strong indication of the soundness of its base heating program. This paper summarizes the thinking that went into the design of our base configuration. Flight test results indicate that pressures, temperatures and heating rates were generally as expected. New techniques have been investigated for generating design data. It has been found experimentally that pressure and thermal fields establish themselves in one to three milliseconds and that data from the "short duration" technique compare favorably with "long duration" type tests. As a result, the new "short duration" technique has become the standard for generating design data for the Saturn vehicle.