The first launch of the Proton launch vehicle was not without problems. A leak in the oxidiser pipeline resulted in nitrogen tetroxide spilling on electrical wires. The question was: proceed with the launch or abort? Chelomei decided to go ahead, and on 16 July 1965 the first UR-500 successfully launched the Proton 1 satellite. In the first hours after launch specialists from OKB-52 could only receive signals in the first hours that indicated the satellite was ‘alive’. However it later functioned normally and provided physics data on ultra-high-energy cosmic particles for 45 days.

At the first launch the rocket was called ‘Gerkules’ (other sources say ‘Atlantis’), as indicated by the large symbol on the second stage skin. This name was however was not taken up.

High energy physics laboratory. Investigation of ultra-high-energy cosmic particles.

Space station 'Proton 3'. Investigation of ultra high energy cosmic particles

First launch of the Proton three-stage variant. The satellite studied the nature of high and ultra-high energy cosmic rays and their interaction with atomic nuclei. Scientific payload 12,500 kg; operated for 100 days in orbit.