Comment by addaon

The Lockheed D-21 drone. Supersonic ramjet without the complexity of scramjet or the cost of turbojet, hamstrung by the need for a manned launch platform (making operations safety-critical… with predictable results) and recovery to get data off it. Twenty or forty years later it would have been paired by a small number of high-cost launcher UAVs and had its cost driven down to disposable, with data recovery over radio comms… but twenty to forty years later there’s nothing like it, and the maturation of satellites means there almost certainly never will be.