Kosmos 51 (Russian: Космос 51 meaning Cosmos 51), also known as DS-MT No.3 was a technology demonstration satellite which was launched by the Soviet Union in 1964 as part of the Dnepropetrovsk Sputnik programme.

Its primary mission was to demonstrate an electric gyrodyne orientation system.

[3] It also carried a scientific research package as a secondary payload, which was used to study cosmic rays and the luminosity of the stellar background.

It was launched aboard a Kosmos 63S1 rocket[4] from Site 86/1 at Kapustin Yar.

[5] Kosmos 51 was placed into a low Earth orbit with a perigee of 262 kilometres (163 mi), an apogee of 533 kilometres (331 mi), 48.8° of inclination, and an orbital period of 92.5 minutes.