V. MAXIMUM VEHICLE SIZE Preliminary layouts were made of the base area of the lifting body for various vehicle size to determine the maximum size. The engine units were mounted 96 inches on centers. The power head diameter is 65 inches. The required dimentional scale to contain the LOX propellant is shown in figure VI-B-2-7 as a function of the number of main engines. Layouts of the base area are shown in figure VI-B-2-8 for 21 and 28 uprated SSME's. The maximum size for 96 inches on center mounting of the SSME's appears to be about 28 units. This results in a heavy lift launch vehicle with a GLOW just under 5,900,000 Kg (13,000,000 pounds) and a payload of 294,000 kg (647,000 pounds) to 185 KM (100 n.mi.) circular orbit. VI. CONCLUDING REMARKS The lifting body launch vehicle with external hydrogen tank provides a single stage to orbit heavy lift launch capability which can be constructed with current technology. Additional payload gains can be achieved within current technology by the use of pressurized tank structure on the launch pad. Studies by Martin Marietta and co-sponsored by Langley Research Center (Contract NASI-13916) indicate that the external tank weights can be reduced as much as 50 percent by the use of membrane tanks. This results in 34,000 to 63,000 Kg (75,000 to 140,000 pounds) gain in payload depending on the HLV size. Single stage to orbit has the advantage of being operationally simple when compared to a two stage and ballistic launch vehicle. It eliminates the staging operation on launch and the in flight start of the main engines. The horizontal landing on a runway is a much simpler recovery technique than ballistic landing on either land or water. Sea recovery of large boost vehicles can not be considered state-of-the-art, whereas, horizontal landing on a runway is a proven technique. Any cost comparison between this configuration and the two stage ballistic should include RDT&E for development of sea recovery and an estimate of the capital investment in ship, docking facilities, handling facilities, and other support requirements for the sea recovery. The expendable external tank probably increases the cost per flight. However, this depends on the cost of manufacturing the tank. There are several advantages of the external tank. Hydrogen leaks are less likely to cause explosions with the extermal tank, and hydrogen leaks were a major problem with the Saturn Launch Vehicle. The
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