• shorten the total transfer time • shorten the duration spent in the radiation belts. An electric propulsion system would then take over so that the system is far more fuel efficient than the purely chemical case. This maneuver is shown schematically in Figure 10.4.10. Figure 10.4.10 Hybrid Orbit Transfer Considering a 8000 km point as the altitude of propulsion system change, and using a Hohmann transfer for the first phase of the maneuver, the AV required are: From LEO to 8000 km; [] m/s, with the same hypotheses than above the mass ratio is then 0.34, considerably less than previously. From 8000 km to GEO, including the same plane change the optimal [] is 3815 m/s. It can be roughly considered that an electrical transfer will use 1.4 times this []. Considering a specific impulse of 5000 s ,the mass ratio for fuel is then 0.09. With this method the total amount of fuel is: 21.5 t. Even with an overhead of 101 for the electrical thruster the gain is still 511. The launch could then be made with only one Energia, greatly decreasing the costs, even when taking in consideration the electric propulsion system cost.
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