Two different sets of cycle points were studied to show the effect of temperature on the mass statement. The first set was picked to emphasize higher efficiency and lower total mass. It uses the same cycle state points as (1). This cycle has a very high turbine inlet temperature (1617 K) which limits the use of lunar materials for components such as the turbine blades or the heat absorber. The second set of temperatures has a more moderate turbine inlet temperature of 1100 K, which is seen in existing engines. This allows better utilization of the lunar alloys (Ni alloys, steel, Cr alloys) and metals like Al and Ti. The efficiency of the cycles was calculated assuming: Compressor efficiency « 0.875 Turbine efficiency * 0.920 Bearing loss & turbine disk cooling efficiency factors - 0.98 The compression and turbine efficiencies used here are from (1) and are viewed as possible but non-conservative values. FIGURE 2.4-1, BRATTON SOLAR CYCLE
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