Editing Interplanetary spaceflight (section)

====Propellant plant on a celestial body====
As an example of a funded project currently{{when|date=October 2019}} under development, a key part of the [[system]] SpaceX has designed for [[Mars]] in order to radically decrease the cost of spaceflight to interplanetary destinations is the placement and operation of a [[physical plant]] on Mars to handle production and storage of the propellant components necessary to launch and fly the Starships back to Earth, or perhaps to increase the mass that can be transported onward to destinations in the [[outer Solar System]].<ref name=spacex-itspresentation201609/>

The first Starship to Mars will carry a small propellant plant as a part of its cargo load.  The plant will be expanded over multiple [[synodic period|synods]] as more equipment arrives, is installed, and placed into mostly-[[autonomous robot|autonomous production]].<ref name=spacex-itspresentation201609/>

The [[SpaceX Mars propellant plant|SpaceX propellant plant]] will take advantage of the large supplies of [[carbon dioxide]] and [[Water on Mars|water resources]] on Mars, mining the water (H<sub>2</sub>O) from subsurface [[ice]] and collecting CO<sub>2</sub> from the [[Atmosphere of Mars|atmosphere]].  A [[chemical plant]] will process the raw materials by means of [[electrolysis]] and the [[Sabatier reaction|Sabatier process]] to produce [[oxygen]] (O<sub>2</sub>) and [[methane]] (CH<sub>4</sub>), and then [[Vacuum distillation|liquefy]] it to facilitate long-term storage and ultimate use.<ref name=spacex-itspresentation201609/>