order not to exceed the allowable radiation dose. A crew rotation passenger module is required for the Earth to LEO and LEO to GEO transfer. The passenger module shown on Figure VI-E-2 first flies in the Shuttle payload bay and then is deployed and docked to the POTV at the LEO operations base. Adequate structural weight allowance is provided for the necessary shielding for safe passage through the Van Allen Belt. Crew size requirements for GEO operations have not been focused sufficiently to allow final passenger size accommodation selection or optimization of rotation timelines and POTV mission costs. For cost estimating purposes, a 75-man module has been selected with a total loaded weight of 19 metric tons. DDT&E and TFU costs of this crev/ rotation passenger module have been estimated at $120M and $6M, respectively. Resupply Module - The third payload characterized for the POTV is the resupply module. Resupply has been defined as replenishment of the GEO station consumables, supplies, and equipment necessary for 180 days. For purposes of sizing, a 25 man/180 day resupply has been selected. The corresponding conceptual resupply module is shown on Figure VI-E-3. It will house the 29 metric tons of resupply items in a 6 metric tons empty weight module at 128 kg/m3 assumed payload density. All three of the above modules are sized to be compatible with the Shuttle payload bay as are the POTV module elements. POTV PARAMETRIC STAGE SIZING A parametric sizing study was performed to determine vehicle ignition weights for various POTV configuration for a range of GEO round trip payload weights. Vehicle sizing guidelines observed are as follows:
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