Size matters - The shell lander concept for exploring medium-size airless bodies

Kurzfassung

Once addressed as a side topic in planetary exploration, the investigation of small solar system bodies has now become one of the corner stones in the international science community in order to study the formation of the solar system and the evolution of life within. For rendezvous spacecraft, small carry-on landers have proven to be valuable assets, and to have a positive impact on the overall mission cost, by avoiding additional complexity of the main satellite and transferring the risk of close surface maneuvers entirely or at least to some extend to an independent deployable system. However, carry-on landers have been designed currently to land on very small bodies only, but medium-size class objects between diameters of 10 - 50 km are of great interest as well. In this paper we classify carry-on landers with respect to their touchdown and operational strategy, evaluate the constraints of ballistic deployments for different target bodies as well as identify the niche for using simple honeycomb impact dampers compared to optional retro-propulsion systems. Further, we introduce the system design of an attitude-controlled Shell Lander using a generic instrument carrier attached to a single ejectable crash-pad with stabilizing capability to protect the instrument carrier from structural damage, limit internal shock loads for sensitive payloads as well as reduce the amount of bounces on the surface. Finally, we present a mission architecture for a reference case to the Martian moon Phobos as well as provide a proof of concept based on laboratory impact tests and a multi-body simulation to analyze touchdown dynamics including terrain interaction, shell-shedding and bouncing.