Passive Management of Deployable Cordage During and After MSL Touchdown

NASA´s next generation Mars rover will land unlike any previous mission. A rocket powered descent stage will lower the rover on three bridles as it flies toward the ground. An electrical umbilical cable will be deployed as well to keep the descent stage and rover in communication. Once on the ground, the rover will cut all soft-good lines, allowing the descent stage to fly clear of the rover. The management of these cables from the moment of rover touchdown until the descent stage has flown clear required a great deal of attention. Slack from these soft- goods could not accumulate on the rover deck and the lines had to avoid both the rover and descent stage during flyaway. The bridles were managed by two systems. One kept tension on all together from within the descent stage. The other, on the rover deck, was able to individually tension each of the bridles. The umbilical management system relied on a single tensioning mechanism within the descent stage. This mechanism was specifically sized such that it simultaneously moved the umbilical away from the rover and descent stage during fly-away. It also had to be sized to manage transient slack at touchdown. As a result, the effects of peak retraction force on these performance characteristics were quantified. Additionally, the umbilical had to be designed to survive the loads associated with deployment and slack management. Finally, a model was developed to characterize the profile of the umbilical during the descent stage fly-away event to understand potential rover deck recontact locations. Those pieces of deck hardware that had the potential to be impacted by the umbilical were identified and recommendations were made as to how to avoid snagging the umbilical.