Chemical orbit transfer vehicles - Options for the future

In the U.S., the Inertial Upper Stage (IUS) and the Centaur will provide the primary technology base for improvements in orbit transfer payload capability and operational flexibility through the late 1980s and 1990s. On the basis of an availability of these two generic stages, a number of potential scenarios is developed. Near-term scenarios take into account IUS-derived options and storable liquid/Shuttle Centaur derived options. In the mid-term it is anticipated that low earth orbit (LEO) on-orbit assembly capability will exist and that stages and spacecraft will be able to be launched separately and be assembled on orbit. In the far-term, in addition to the technological base established by the development of more advanced upper stages than exist today, substantial improvements in ground to LEO payload capability are likely to be realized.