So an on board processor essentially looks at what motions need to be executed and combines these motions and figures out what commands to send to the motors 600 times a second.

In his lab at Penn, Vijay Kumar and his team build flying quadrotors, small, agile robots that swarm, sense each other, and form ad hoc teams for construction, surveying disasters and far more.

Initially, many different designs were considered, including an unconventional project with two main rotors, placed with engines on tips of wings (in perpendicular layout), and with an additional pusher propeller on the tail.

Most French roundabouts now have give way signs for traffic entering the circle, but there remain some notable exceptions that operate on the old rule, such as the Place de l'Étoile around the Arc de Triomphe.