was 117.35 meters per second (385 feet per second). The shroud for the payload was considered to be included in the 453.59 metric tons (1,000,000 pounds) of the payload. The initial concept for the winged vehicle consisted of a heat sink straight wing booster and a delta winged second stage. The booster would be flown back to the launch site; air breathing engines (ABE's) of 222,411 newtons (50,000 pounds) thrust were used in the flyback simulation. The upper stage did not use ABE's but was designed to reenter the earth's sensible atmosphere after one orbit and glide back to the launch site. This first sizing effort resulted in a launch vehicle using LOX/RP-1 booster engines and weighed over 32 million pounds at lift off. Mr. W. Taub of the Spacecraft Design Division provided layout support for the transportation system sizing effort, and several of his drawings of this initial vehicle are included. Figure 1 shows views of the booster stage, and incorporates some unique concepts. The ABE's are shown stored in the nose cone of the booster stage, deployable for powered flyback. Landing gear stowage areas are given and an engine packaging scheme is shown. Figure 2 gives similar views of the delta winged upper stage. The stages are shown in a stacked launch configuration in Figure 3. A conceptual "piggy-back" launch configuration is provided in Figure 4, and Figure 5 shows a launch arrangement for a parallel burn lift off. No trajectories were flown for the parallel burn operations mode, but the illustration shows the height of the lift off configuration could be considerably reduced. A further reduction in launch configuration height is shown in figure 6 which shows the payload in two modules; one mounted on each wing of the upper stage. Such diverse conceptual designs as these by Mr. Taub are an integral part of the definition of a viable launch vehicle. Figure 7, using the parallel burn launch configuration, provides an illustration of the HLLV winged launch vehicle mission profile. After several simulations certain parameters were selected and held constant in order to equitably evaluate both the LOX/RP-1 and the L0X/LH2 flying booster concepts. The booster wing loading was established at 5267 newtons per square meter (110 pounds per square foot) of wing area, the leading edge sweep was selected as 10 degrees, and a landing speed of 92.6 meters per second (180 knots) was chosen. The thrust to weight ratio at lift-off was 1.3 for all cases; the initial thrust to weight ratio of the upper stage was 0.97. Subsequent iterations also led to the selection of a straight wing for the upper stage with the same loading; its leading edge sweep was also 10 degrees. Trajectory constraints for all simulations were:(l) 4 g maximum acceleration during ascent, and (2) maximum dynamic pressure of 31.122 newtons per square meter (650 pounds per square foot). The LOX/RP-1 vehicle was sized to a gross lift off weight (GLOW) of 13,359 metric tons (29,451,478 pounds). This weight includes an allowance for growth in the booster stage, which was fixed at twenty percent of the booster dry weight. A weight and performance summary for this vehicle is given in Table 5; the trajectory time histories are presented in
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