If manned missions to the planets are to be considered at some time in the future, as has long been imagined, it appears to be reasonable to explore the feasibility of carrying out a manned mission to an asteroid as an intermediate step between lunar and planetary missions. If study shows that it is possible to conduct such a mission with Apollo-type hardware, and if the answer to the first question is yes, then an asteroid flight should probably be considered while Apollo-type facilities are

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... ill in existence. Once these facilities have been dismantled, it may be many years, perhaps a generation, before a new era in space exploration would make such a manned flight possible.