Table 5.GEO Tug Design Summary Design Dry Mass (kg)Wet Mass(kg) Power (w) Delta-V(km/s) Total Utility Cost(MS) Biprop one-way 1300 11700 1200 5.5 0.65 510 Cryo one-way 1100 6200 1200 7.1 0.69 310 Electric one-way 700 1000 3600 9.8 0.65 130 Electric cruiser 700 1100 3600 12.6 0.69 140 Bipropellant Cryogenic Wet Mass:11689 kg Wet Mass:6238 kg Electric-One way Electric-Retum Trip Wet Mass:997 kg Wet Mass:1112 kg Fig.11.Cryo one-way tug,showing extremely large fuel tanks;Bi-prop tug appears similar Fig.13.Comparison of all GEO Tug designs C&DH 0% 1%Power 11% Propulsion (dry) 2% Structures Mechanisms 18% Thermal 5% Mating System 27% Fig.12.Electric Cruiser(GEO round-trip tug) Fig.14.Mass breakdown of Electric Cruiser design The bi-prop one-way tug is very large and therefore The cryo one-way tug is significantly lighter than the very expensive.It is also very sensitive to changes in biprop tug,but is almost as large due to low fuel any of the design assumptions:any increase in dry mass density.It would have a very limited life on-orbit due causes a very large increase in fuel required.There is to the need to keep the fuel cold.It is less sensitive to some danger that such a design would not"close"(i.e. mass fractions and other assumptions,but still cannot the required fuel mass would become infinite)if the dry make a round trip to GEO. mass fraction or delta-V requirements were greater than anticipated.The best that can be said is that such a The electric one-way and round-trip tugs seem to be vehicle could fill a niche for missions where a large practical,versatile designs with reasonable sizes and payload must be moved quickly using existing costs.The electric designs do have the drawback of technology. slow transit time,but they appear to be well suited for 9 American Institute of Aeronautics and Astronautics9 American Institute of Aeronautics and Astronautics Table 5. GEO Tug Design Summary Design Dry Mass (kg) Wet Mass (kg) Power (w) Delta-V (km/s) Total Utility Cost (M$) Biprop one-way 1300 11700 1200 5.5 0.65 510 Cryo one-way 1100 6200 1200 7.1 0.69 310 Electric one-way 700 1000 3600 9.8 0.65 130 Electric cruiser 700 1100 3600 12.6 0.69 140 Fig. 11. Cryo one-way tug, showing extremely large fuel tanks; Bi-prop tug appears similar Fig. 12. Electric Cruiser (GEO round-trip tug) The bi-prop one-way tug is very large and therefore very expensive. It is also very sensitive to changes in any of the design assumptions; any increase in dry mass causes a very large increase in fuel required. There is some danger that such a design would not “close” (i.e. the required fuel mass would become infinite) if the dry mass fraction or delta-V requirements were greater than anticipated. The best that can be said is that such a vehicle could fill a niche for missions where a large payload must be moved quickly using existing technology. Fig. 13. Comparison of all GEO Tug designs Structures & Mechanisms 18% Thermal 5% Mating System 27% Propellant 36% Link 1% Propulsion (dry) 2% Power 11% C&DH 0% Fig. 14. Mass breakdown of Electric Cruiser design The cryo one-way tug is significantly lighter than the biprop tug, but is almost as large due to low fuel density. It would have a very limited life on-orbit due to the need to keep the fuel cold. It is less sensitive to mass fractions and other assumptions, but still cannot make a round trip to GEO. The electric one-way and round-trip tugs seem to be practical, versatile designs with reasonable sizes and costs. The electric designs do have the drawback of slow transit time, but they appear to be well suited for