The Rotary Rocket did fly three test flights and a composite propellant tank survived a full test program, however these tests revealed problems. For instance, the ATV demonstrated that landing the Rotary Rocket was tricky, even dangerous. Test pilots have a rating system, the Cooper-Harper rating scale, for vehicles between 1 and 10 that relates to difficulty to pilot. The Roton ATV scored a 10 — the vehicle simulator was found to be almost unflyable by anyone except the Rotary test pilots, and even then there were short periods where the vehicle was out of control.