Every ambitious engineering project contains unanswered questions.
Recognising these questions is not a weakness.
On the contrary, clearly identifying the limits of current knowledge is an essential characteristic of rigorous engineering practice.
The purpose of this chapter is recording the principal technical questions that remain open at the current stage of the Radixora project.
These questions should guide future research activities, prototype development and pilot projects.
As new evidence becomes available, the questions presented here should gradually evolve into validated engineering knowledge.