The dynamics of [quadrotor robots] are quite complicated. In fact, they live in a 12-dimensional space.

Kumar is underscoring that even a seemingly simple flying robot has a high-dimensional state: a quadrotor’s position and orientation (6 degrees of freedom) plus their corresponding linear and angular velocities (another 6) yield a 12-dimensional state space. Calling the dynamics “complicated” highlights the control challenge: the vehicle is underactuated (four rotors controlling six DOF), strongly coupled, and sensitive to disturbances, so stable flight and agile maneuvers require sophisticated modeling, estimation, and feedback control. The remark also serves a pedagogical purpose—translating an engineering reality into an intuitive idea (“living” in a 12D space) that conveys why quadrotor autonomy is nontrivial.