In the 1990s elaborate plans have been made on how Mars missions can profit from ISRU technology in the Design Reference Missions (DRMs) : By producing propellant in situ on Mars, the start mass of the mission and the mass of the lander vehicle can be significantly reduced . Furthermore, in situ propellant production provides more flexible surface exploration capability and the possibility of longer mission durations due to the possibility of refuelling rovers . In addition, longer mission durations reduce the mission risk due to fewer launches . It is even conceivable that the necessity for live supporting facilities may become redundant . For example, ISRU systems include the production of O2 via electrolysis , which can provide O2 for the human habitat in the event of leaking O2 tanks. Nevertheless, ISRU does require higher energy input to support the operation of the required process units, including compressors, electrolysis, heat exchangers, excavators, haulers, and so forth . In addition, the employed systems must be capable of long service live, since equipment replacement requires costly transport missions from earth . The DRM outlines two distinct mission scenarios for a prolonged human stay on Mars: 1. A single site habitat for human presence in combination with multiple exploration missions and 2. several habitat sites during multiple Mars missions . The latter scenario necessitates the construction of multiple facilities with the required infrastructure including potential ISRU capabilities.