for current and future technology projections, and the number and size of the main propulsion rocket engines. The payload chosen to size the heavy lift launch vehicle is the modified orbiter with 45,000 Kg (100,000 pounds) payload. The gross weight of this payload is about 129,000 Kg (283,800 pounds) (see table VI-B-2-9). The weight scaling factors used for structure and system weight estimates are based on current technology. Where applicable the weight scaling factors were based on shuttle technology. Scaling factors obtained from several studies and the shuttle project weight statements are shown in table VI-B-2-1. In each category the first scale factor listed is the one used. The sizing studies were carried out using the current shuttle SSME's as the main propulsion unit and with an uprate version of the shuttle SSME's. The uprated version consisted of increasing the chamber pressure from 3,000 to 4,000 psi. The characteristics of the current and uprated engines are shown in table VI-B-2-2. The data for the uprated engine were supplied by the JSC Propulsion and Power Division. The launch simulation used in the sizing analysis consisted of two dimensional integrated trajectories with a gravity turn (zero angle of attack) to 30,480 meters (100,000 feet) altitude and optimum steering above 30,480 meters (100,000 feet) altitude. The thrust to weight at lift off was constant at 1.25. Launches were due east at 28.5 degrees latitude to 111.1 KM (60 n.mi.) altitude above the equatorial radius. The external fuel tank was staged at 7,823 meters/seconds (25,665 feet/ seconds) and a flight path angle of 0.5 degrees. These staging conditions result in a tank impact in the Indian Ocean if launch is from KSC. The orbit maneuvering propellant requirements for circularization in 185 KM (100 n.mi.) orbit and deorbit was calculated for a specific impulse of 313. The 1962 standard atmosphere was used for drag calculations. The drag coefficient as a function of Mach number is given in table VI-B-2-3 for the lifting body and the external tank. The forebody drag coefficient is given for the lifting body and this is combined with the power on base pressure to obtain the total drag. The drag coefficient for the external tank is power off total drag. It was assumed that there is no power on effect on the base of either the external tanks or payload. The drag calculations are based on a reference platform area for the lifting body of 453.2 square meters (4,878 feet squared) and is varied according to the square of the scale. The vehicle scale is determined by the LOX volume and the system volume requirements given in table VI-B-2-4. The lifting body scale factor is the cube root of the ratio of the total volume to the reference volume of 2,738.2 cubic meters (96,700 cubic feet).
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