Sustained operation lunar trajectories

The Apollo trajectories and the Saturn V delivery system provided the necessary transport to the Moon and return in the late 1960s. With a near-Earth-orbit space infrastructure established (see Chapter 5) it is not necessary to have a direct flight to the Moon with expendable hardware. Both Russia and the United States contemplated a Moon base and the systematic flights necessary for its support and staffing. Figure 6.6 is a composite of both approaches, based on briefings and reports from the early 1980s. The figure is from a brief given by V. Gubanov to the space organization of the former Soviet Union, and presented at the 1984 European Space Conference in Bonn, Germany. The original figure is in Cyrillic and has been translated. The presentation by V. Gubanov describes a multi-step approach that begins with an "artificial" Earth orbital station, then moves to the Moon as the Earth's "natural" orbital station. After the Moon station is established and opera tional, the tested and proven Moon facilities are used to design a Mars facility, and the Moon is used as a launching platform for the human expedition to Mars. In the original Gubanov brief, there is a single transportation vehicle that moves from LEO to the lunar parking orbit and returns. In the Science Applications International Corporation (SAIC) study from 1984 for an initial operational Moon base, a two-stage transportation system using Orbital Maneuver Vehicles (OMVs) is proposed [SAIC, 1984].

Earth-based launchers deliver the lunar base materials to LEO for integration to an OMV. The first OMV puts the system into an Earth elliptical orbit, and the second stage OMV stages at the correct time for another Earth elliptical orbit that intersects the lunar sphere of influence, Figure 6.4. Both OMVs return to LEO for continued use. There is the option for the lunar payload to be transferred to a lunar surface delivery vehicle in lunar orbit, or to descend directly to the lunar surface, as the mission requirements dictate. Just as the Earth launchers can deliver to LEO, or return lunar payloads from LEO, there is a lunar launcher that delivers and returns payloads from low lunar orbit (LLO). Since the second-stage OMV must execute an aero-braking maneuver in the Earth's upper atmosphere, it must have at least a capsule configuration for braking with a finite lift-to-drag ratio (such as the Apollo heat shield or a Mars aero-braking design with an asymmetric cone configuration). Technologically, here the choice is between reusable heat shields or ablatives, the latter requiring refurbishment or replacement after each re-entry flight.

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