How many tanker launches are required to top off a single Starship for Mars transit, based on propellant calculations by Donald Rapp?

Roughly twelve tanker launches

Donald Rapp, a chemical engineer, calculated the substantial propellant requirement for a single Mars-bound Starship to complete its transit and subsequent maneuvers. This calculation establishes that approximately 1,200 tons of propellant are necessary. Since the Starship architecture relies on orbital refueling via tanker Starships, this tonnage translates directly into the required number of supply missions. Specifically, the estimation cited is that roughly twelve tanker launches must successfully dock and transfer fuel to successfully top off one interplanetary vehicle before it can even attempt departure toward Mars. This massive logistical requirement highlights orbital refueling as a critical, yet unproven, hurdle preceding any deep space crewed flight.