Experimental Enhanced Upper Stage (XEUS): An affordable large lander system

The Experimental Enhanced Upper Stage (XEUS) offers a path to reduce costs and development time to sustainable activity beyond LEO by equipping existing large cryogenic propulsion stages with MSS VTVL propulsion and GNC to create a large, multi-thrust axis lander. Conventional lander designs have been driven by the assumption that a single, highly reliable, and efficient propulsion system should conduct the entire descent, approach, and landing. Compromises in structural, propulsion, and operational efficiency result from this assumption. System reliability and safety also suffer. The result is often an iterative series of optimizations, making every subsystem mission-unique and expensive. The XEUS multi-thrust axis lander concept uniquely addresses the programmatic and technical challenges of large-mass planetary landing by taking advantage of proven technologies and decoupling the deorbit and descent propulsion system from the landing propulsion system. Precise control of distributed, multi-thrust axis landing propulsion units mounted on the horizontal axis of a Centaur stage will ultimately enable the affordable deployment of large planetary rovers, uncrewed base infrastructure and manned planetary expeditions. The XEUS lander has been designed to offer a significantly improved mass fraction and mass to surface capability over conventional lander designs, while reducing airlock/payload to surface distances and distributing plume effects by using multiple gimbaled landing thrusters. In utilizing a proven cryogenic propulsion stage, XEUS reduces development costs required for development of new cryogenic propulsion stages and fairings and builds upon the strong heritage of successful Centaur and MSS RLV flights.