Small lunar lander/hopper performance analysis

The goal of this paper is to describe a first-order performance analysis of a lunar hopper. A hopper is a vehicle that has both landing and surface mobility capabilities on a single platform. Unlike rovers, which traverse the lunar surface while in contact with the ground, hopping reuses the landing propulsion system to lift back off again and ¿hop¿ over the lunar terrain. Hopping, as a form of surface mobility, is a novel concept. As such, analysis must be performed to assess how it would fit with an overall lunar landing system architecture. Two trajectory categories are investigated to perform this assessment: the ballistic hop, where the vehicle launches itself into a ballistic trajectory toward the destination, and the hover hop, in which the vehicle ascends and maintains a constant altitude as it travels toward its desired location. Initially, parametric studies of the ballistic and hover hop are carried out in order to make observations about the performance of each hop. Using this data, it is possible to investigate the fuel-optimal hop trajectory. The delta-V costs for the ballistic and hover hops are compared for hop distances between 500 meters and 5000 meters, and in this range it is found that the ballistic hop and hover traverse have comparable delta-V costs. For the entire hop maneuver, however, the hover hop will always be the more delta-V expensive option due to the ascent and descent phases. Nevertheless, this does not rule out the hover hop as a feasible option due to its operational advantages over the ballistic hop.