To compare the continuous operation cycles Figure 3.4 is repeated as Figure 4.23. In Figure 4.23 weight ratio to LEO, that is the takeoff gross weight divided by the on-orbit weight, is represented for different engine cycles as a function of the net oxidizer to fuel ratio. These divide into two distinct groups. The rocket-derived propulsion represented by cycles: rocket, air augmented rocket and ram rocket. For the rocket-derived cycles the oxidizer-to-fuel ratio is essentially constant at a value of 6. As a ram rocket, the weight ratio of LEO decreases from 8.1 to 6.5. There is only a minimal payoff for the air augmented rocket as without burning the oxygen in the air, there is insufficient thrust boost to make a significant difference in weight h eg h eg
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