$4xl08. and research $xlO9 447 t of material are considered for space shuttle payload [6], However, additional mass for transportation vehicles would have to be carried by the shuttle. Cost estimates assume research is necessary for only 15 t of the total equipment mass of 107 t, and construction costs are ignored, as are costs of transportation beyond low earth orbit. The stated cost of $4 x 108 for 16 shuttle flights for the 447 t of equipment and fuel [7] indicates an assumed cost of This will have increased to $9xl0^/flight by 1985 (uncertain by 10%), so the cost of shuttle transportation can be recomputed as since the shuttle carries 301 payload per flight. The research cost has also increased above that given in S.S.I., in which shuttle research and development costs are taken as a basis for estimation [8], This cost is given as $6xl0^/t, but the cost of research and development in the shuttle program has increased from about $6xl09 estimated in 1980, the date of the S.S.I. plan, to S101® (uncertain by about 20%). The research cost per unit mass can therefore be recomputed to be 60% higher than originally estimated, or and the research cost is now The sum of these two cost components, which are the only ones considered in the original S.S.I. plan, was originally stated as $1.3 x 109; it should be revised to Extended S.S.I. Plan Assumptions Assumptions used in the extended plan follow.
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