Elements of a Mars transportation system

Earth to Mars transportation requirements are derived for a permanent Mars base of 20 people operating in the 2035 time frame. In order to satisfy these requirements, various transportation modes are developed assuming an existing space infrastructure including propellant tankers, crew and consumable transfer vehicles, orbital facilities and extraterrestrial propellant factories. These transportation modes are compared with respect to total propellant requirements, number of vehicles required, flight times, frequency of opportunity and several other characteristics. Directions for further studies and analysis are indicated.