  We propose a context-sensitive grammar for the systematic exploration of the
design space of the topology of 3D robots, particularly unmanned aerial
vehicles. It defines production rules for adding components to an incomplete
design topology modeled over a 3D grid. The rules are local. The grammar is
simple, yet capable of modeling most existing UAVs as well as novel ones. It
can be easily generalized to other robotic platforms. It can be thought of as a
building block for any design exploration and optimization algorithm.
