NASA's plans for manned missions to the moon and Mars

Issues, problems, and potential solutions of the lunar and Mars missions which will be undertaken in the first decade of the next century are discussed. Arguments are made for the feasibility and usefulness of a lunar base, and an evolutionary approach to a manned Mars mission involving a preliminary mission to Phobos is outlined. The Shuttle Z concept for both moon and Mars missions which involves a dual use of a spacecraft transfer stage operating also as a booster third stage is defined.