It is a variant of the Progress spacecraft, derived from the Progress-M, but modified to carry more UDMH and N2O4 propellant for refuelling the International Space Station instead of other cargoes such as water.
[2] This propellant can be transferred to the Space Station's own propulsion system through fluid connectors in the docking ring, or it can alternatively be used by the Progress' thrusters to boost the station altitude or to change its orientation, or attitude, in space.
In addition to propellant, the spacecraft can also carry up to 1,800 kilograms (4,000 lb) (6 cubic meters volume) of supplies in its forward pressurized cargo module (including a maximum of 40 kilograms (88 lb) of compressed air), but the combination of pressurized cargo and refuelling propellant cannot exceed 2,500 kilograms (5,500 lb) or the maximum capability of the launch vehicle.
Of the eleven 11F615A55 spacecraft launched, three flew to Mir, with the remainder being used to resupply the International Space Station.
[4] Ten of the spacecraft were used for traditional resupply missions, whilst the eleventh, Progress M1-5, was used instead to deorbit the Mir space station.