Salyut 2 (OPS-1) was a Soviet space station which was launched on April 3, 1973. It was the first Almaz military space station to fly. It was designated part of the Salyut programme in order to conceal the existence of the two separate space station programmes.
Three days after the launch of Salyut 2, the Proton’s spent third stage exploded. Thirteen days after launch Salyut 2 began to depressurise, and its attitude control system malfunctioned. An inquiry into the failure initially determined that a fuel line had burst, burning a hole in the station.It was later discovered that a piece of debris from the third stage had collided with the station, causing the damage.
It decayed from orbit by 28 May 1973, without any crews having visited it.