Effects of passive de-orbiting through drag and solar sails and electrodynamic tethers on the space debris environment

This paper assesses the net effect on the long-term sustainability of the space debris environment by answering the following questions: which sail or tether size do we need for deorbiting, is that achievable with current technologies? How does the cumulative collision risk scale with the sail size, and deorbiting time? How can we model a collision involving large appendages? What happens to the space debris environment when using sails or tethers massively? Can we perform collision avoidance manoeuvres in this case?