Heading out on the Space Oregon Trail

I came across a recently published post on Centauri Dreams on the The Spacecoach Equation.  The short story is that by using consumables (water, CO2, gasified trash) as propulsion fuel rather than traditional propellants, the total mass of a mission would be radically reduced.  The mass reduction would be more than an order of magnitude improvement above baseline designs which would use external fuel stages.