Lockheed D-21

The Lockheed D-21, also known as TAGBOARD, was an unmanned reconnaissance drone developed from A-12/M-21 Blackbird-era technology. The CIA museum notes that Lockheed built two M-21 motherships and 38 drones for surveillance missions over denied territory, while NASA later studied D-21 reuse concepts. The current combat UAV label is imprecise; the platform was a strategic reconnaissance drone, not a UCAV.

The drone was intended to fly a programmed route, collect imagery, eject a payload capsule, and be expended. Launch arrangements evolved after the M-21/D-21 accident, including B-52 carriage for D-21B variants. Its design pushed the limits of materials, propulsion, guidance, and mission recovery for an unmanned system of its era.

The platform showed what high-speed unmanned reconnaissance might achieve, but reliability, recovery, and mission execution challenges limited operational success. It remains important as a precursor to later unmanned intelligence systems and as an example of Cold War experimentation when satellites and manned overflight had distinct limitations.