(USSR)

Notes: Despite the passage of time, little is still known of this early 1960s strategic bomber project other than the Soviet leadership regarded it as a spectacular failure. The massive intercontinental warplane first flew in October of 1959. It was designed to cruise at Mach 1.5; however it‘s maximum attained speed during tests was only Mach 1.39. It was powered by four huge Zubets jet engines, one under each wing and one on each wingtip.

Aerodynamic science of the day lagged far behind the goals of this project. The M-52 designation was assigned to the prototype after modifications to the engines, which still failed to deliver the desired results. The project was cancelled in 1960. The planned armament, a huge nuclear-armed delta-winged cruise missile designated “M-61” never made it to the flight test phase and was itself also cancelled.