For SPS LEO construction, the POTV is regarded as a special purpose device due to the long trip times associated with the COTV[_. The number of people traveling to GEO will be less due to the large LEO construction crew and therefore infers a smaller passenger carrying vehicle than the POTVq. In addition, this common stage O2/H2 vehicle takes advantage of the economies of the COTV|_ by having its down propellant delivered to GEO. The range of POTV|_ is given as follows: Personnel and Priority Cargo Launch Vehicle (PLV) - The PLV will be utilized for transport of all personnel from Earth to LEO and return. The PLV will be available for small loads of priority cargo, but this capability is not considered in this scenario exercise. Basically, the PLV is an upgraded Shuttle with the two baseline SRB's replaced by a "liquid replacement booster" (LRB) that operates in a series burn mode with the Orbiter/ET. The LRB is reusable following a ballistic entry and parachute/1anding rockets water splashdown. The range of PLV characteristics is given as follows and is consistent with in-house studies by Rockwell International and Boeing. Orbital Propellant Storage/Transfer For the space transportation scenario, it was assumed that all COTV's and POTV's are based at LEO for refurbishment, refueling, and other flight vehicle turnaround activities. It was also assumed that all OTV propellants are delivered by HLLV to a LEO depot "tank farm" for propellant storage before OTV refueling. There will be propellant losses associated with this storage/transfer activity in terms of daily boil off, transfer residuals, and chilldown losses. These LEO propellant losses have been estimated as 30% such that for every kilogram of OTV propellant required at LEO, 1.3 kilograms must be delivered to LEO by the HLLV. In the case of the POTVl, the crew rotation mission requires that the second stage be refueled at GEO; therefore, a more modest tank farm is assumed available at GEO. The total GEO propellant loss has been estimated at
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