PERFORMANCE REQUIREMENTS AND KICKSTAGE DISPOSAL OPTIONS FOR A CISLUNAR GATEWAY STATION TRANSFER VEHICLE

摘要

The notion of human missions to libration points has been proposed for more than a generation. A human-tended Gateway Station at the cislunar (L_1) libration point could support an infrastructure expanding human presence beyond low Earth orbit and serve as a staging location for human missions to the lunar surface, Mars, asteroids, and other libration points. Human occupation of the Gateway Station requires a transfer system in the form of a Libration point Transfer Vehicle (LTV) designed to ferry the crew between low Earth orbit and the Gateway Station. Assuming the LTV uses an expendable kickstage for the Earth orbit departure maneuver, a key problem in the design of such a system is the economical and safe disposal of that kickstage. After investigating the basic performance requirements for delivering the crew vehicle to L_1 , several options for kickstage disposal are explored. These include: return to Earth (ocean impact), lunar surface impact, lunar swing-by into heliocentric orbit, and insertion into a long-lifetime geocentric parking orbit. If there is no radioactive or comparably hazardous material in the kickstage, results indicate that the best option from the standpoint of public safety, aesthetics, and economy is direct return to one or the other of two mid-ocean lines on the Earth surface. Because L_1 is an unstable libration point, another important problem involves potential unplanned return of the Gateway Station (or associated support spacecraft parked at L_1), brought on by failure to perform required orbit correction maneuvers. Accordingly, another part of the study determined orbit lifetimes for vehicles at L_1 having velocities of varying magnitude and direction relative to the libration point.