Fuel depot prepositioned in Lunar perpetualy dark South pole crater
This is a pre-ISRU scenario
Preposition cryogenic propellant in the perpetually dark lunar crater, use the commercial sector to land the propellant. Send the propellent one way. Zubrin recently suggested Moon Direct using Falcon Heavy with a 6 Kilometers /s earth to the moon and back again. Our idea makes this vehicle free of ISRU, Our idea perhaps reduces the mass of the proposed Zubrin vehicle, Our idea reduces the mass of the Propellent lander because the lender needs much less zero boil-off requirements. We think The ACES Zeus lander makes sense. It would need some boil off to power the ICE engine.
When the dark crater fuel depot needs to transfer fuel it would do a hop from its shadow up to the crater rim to land near the human crew vehicle. The ACES Zeus ICE engine could allow this vehicle to do some science of its immediate surroundings while in the crater shadow. This would become a fleet of vehicles that would be used again after ISRU come online. After ISRU come online the idea of the propellent lander staying in the shadow for insulation might be kept and would do the Hop to the sunlight to refuel the human crew or propellant transfer vehicle to cislunar space.
So Gear Ratio study?
The dark crater should allow for a more massive fuel depot with less vehicle mass fraction, right? less insulation or the delivered fuel is the same and less mass to the launch vehicle Trades study! The Zubrin Lunar direct assumes ISRU well we do not so our architecture would result in many oneway landed ACES Xeus landed systems. An early BKutter paper suggested these would be used on the Lunar surface habitats or yes storage of liquids
At first glance, Our idea does not reduce the mass of the Zubrin human crewed vehicle and would not reduce the gear ratio. You would want to increase the delivered propellent by reducing insulation mass? If not then you would need a smaller Earth launch vehicle to loft the lunar crater fuel depot