On display at Museum of Flight. Article 134 is the first of two built in 1963 and the only one to survive a test loss. It was retired after 80 flights. D-21 'Tagboard' drone #510 for unmanned recce is attached to the spine launch pylon. Launch of these drones at M 3.3 by the Launch Control Officer (LCO) seated in the aft cockpit proved difficult. The 13.1 m titanium D-21 with a max weight of 4,990 kg was powered by a Marquart XRJ43-MA-20S4 ramjet engine that could fly the drone in excess of M 3.3 and 80,000 ft for around 90 min. Only the nose section with the cameras and film was recoverable.