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Ropefent Weight/Spacecraft Weight GEO to GSO

□ Hypergolic

□ Thermal Nuclear

□ Solar Electric

■ Nuclear Electric

Figure 5.9. Ratio of total propellant weight/satellite weight.

Table 5.9. Launcher and OMV propulsion options.

Launcher propulsion

OMV propulsion

Hydrogen/oxygen rocket based on the P&W XLR-129

LACE rocket based on the P&W XLR-129

Rocket ejector ram/scramjet to M = 10

+ hydrogen/oxygen rocket Rocket ejector ram/scramjet to M = 12 + hydrogen/oxygen rocket

Hypergolic, restartable, long-life rocket closed turbopump cycle rocket Hydrogen/oxygen restartable, long-life expander or closed-cycle rocket Electric MHD thruster with lithium fuel powered by solar panels Electric MHD thruster with lithium fuel powered by nuclear reactor

1 mass unit of propellant to LEO. However, the real advances occur when both the launcher and the OMV propulsion is improved.

Figure 5.10 focuses in on the electric propulsion for the OMV and the more efficient launcher propulsion systems. Now the propellant required to deliver 1 mass unit of propellant to LEO is between 3.5 and 0.5. Now it becomes practicable to deliver propellant to LEO as the propellant cost is no more than the propellant to deliver a unit mass of payload in a commercial transport. Although it is nearly prohibitive in terms of hypergolic space rockets and conventional launch rockets to deliver significant quantities of orbital maneuver propellant to LEO (the actual

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