C. Personnel and Priority Cargo Launch Vehicle The PLV will be utilized to transport all personnel to LEO and can, in addition, fulfill high-priority delivery functions of a modest scale. The approach taken in this study was to modify the current Space Shuttle vehicle to fulfill these requirements. Past studies have indicated that the baseline Shuttle system can be improved in both payload capability and operating cost by replacement of the two solid rocket boosters with a liquid rocket booster (LRB) utilizing oxygen and kerosene propellants. If available for heavy lift vehicle use, a new, more efficient, oxygen/hydrocarbon engine can be advantageously employed to increase the payload capability of this growth Shuttle booster or enable a decrease in propellant requirements. The LRB is a 33-ft-diameter stage with integral propellant mounted beneath the Shuttle external tank (ET). It uses four F-l class engines and provides series burn operation. The stage is recoverable down range following a parachute water landing. The reference mission for the study is the Shuttle Reference Mission 1, with an Orbiter modified for a payload of up to 100 000 pounds (45 metric tons). The LRB is sized according to weight estimating relationships based on Saturn technology. The Orbiter is modified to include the additional structural weight necessary to accommodate the increased up payload. Both series burn and parallel burn Shuttle/LRB configurations were studied. The series burn mode achieved minimum gross lift-off weight (GLOW) in the design cases simulated and is expected to be significantly less expensive due to the smaller expendable ET. The design simulation designated EDIN0505 was chosen as the reference PLV configuration. This configuration and characteristics are shown on figure VI-4. A concept has been proposed by Rockwell International for a 68-passenger Orbiter transport vehicle. Although as many as 100 passengers may be possible for a modified Orbiter, a range of 40 to 80 passengers is assumed in the present study. The estimated cost per flight is $8 to $12 million. D. Cargo Orbital Transfer Vehicle The COTV is a space-based system designed for transporting from LEO to GEO all the material required for SPS construction or assembly, but does not transport personnel. Two basic COTV systems may be identified, distinguished by whether or not power is available from the payload. The first system, COTV^ applies to SPS configurations that involve construction at LEO, either total or in modules, which can provide energy for propulsion for orbital transfer. The second system, COTVg, applies to SPS configurations that involve primary construction at GEO and consequently cannot provide payload power for transfer from LEO to GEO.
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