Fuel costs, propulsion systems and interplanetary supply chains

A perspective on the economics of space logistics in a future state where there are continuous supply routes between Earth and outlying bodies in the solar system is discussed. In particular, the dependence of the cost of transport on specific impulse and % of non-fuel mass as cargo is discussed. Also, a simple way to calculate the optimal cargo mass of a transport ship carrying a commodity with constant demand is proposed as well as qualitative issues regarding backhaul and inventory that space logistics planners will have to one day confront.