The interorbital vehicle shall have a modular propulsion system. Electric propulsion systems shall also be applied besides chemical ones. Potential various power-supply systems are explained. Consisting of a H 2 O 2 —stored in pressurized tanks—turbine-generator power supply system and an ion propulsion system with Xe or a plasma propulsion system with Ar this “indirect” closed loop system is compared with a conventional chemical one by the calculation of a system-mass-break-even point. Depending upon minimum requirements like velocity increment the described propulsion systems can be attributed to various scenarios.