The column labeled subtotal in Table 12 in the SP-428 plan [46] gives the total masses brought to low earth orbit from the earth for the case considered here, in which no materials from earth are required in solar power satellite construction. The mass includes equipment, chemical propellants, crew and baggage, and consumables. The mass of the last three, through 1991, is The cost of chemical propellants and consumables will be neglected. The mass in the subtotal column, totaled through 1991, is 45,970.1 t, so the remaining mass to be accounted for from earth, which consists of equipment and supplies, is 43,979.1 t - 19,091 t = 26,879.1 t. Of this, 12,896 t of equipment other than vehicles is shown in all the other tables of the plan of SP-428. Some additional equipment from earth for modification of external tanks for use in propellant storage may be required; there is only provision for 3 sets of H and O storage tanks in the tables. The mass of the conversion equipment for each external tank is 4.15 t; [47] if 10 additional storage sets are required, the mass from earth for the conversions is The total mass from earth for vehicles is 9876.1 t [48], The total mass of equipment from earth so far considered is Mass from earth which remains to be accounted for is In the extended S.S.I. plan, the mass of equipment constructed on earth was 2467.765 t, and the cost of construction was assumed as $10^/t. Since the mass of equipment constructed on earth in the SP-428 plan so far considered is 9.24 times as
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