Orbital transfer vehicles - An overview

A review of past high energy upper stage evolution leading to the first earth-lunar transfer vehicle, the Apollo S-IVB, is given and the current STS (Space Transportation System) upper-stage characteristics are discussed as a basis for future OTV (Orbital Transfer Vehicle) planning. Attention is given to requirements, operational factors, design features, and program alternatives as a background for a general review of OTV planning considerations for STS performance enhancement. The alternative discussed and other issues are under study by NASA and will be carefully assessed during the next few years as options are considered versus mission needs.