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 {|cellspacing=10 cellpadding=15 width="100%" border="0" utilize the. . . Soyuz rocket to insert it [into orbit].”
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The Progress orbital module (“cargo bay”) was two hemispheres welded together through the intermediary of a short cylindrical section (very similar to the Soyuz orbital module). The forward hemisphere contained the docking unit and the port connecting the orbital module to the space station. Unlike Soyuz, Progress had no hatch in the aft hemisphere. The orbital module contained a supporting framework to which large equipment (such as air regenerators) was attached. Small items were packed in bins.

The probe and drogue docking unit used on Progress resembled the Soyuz unit. The chief difference was provision of two ducted mating connectors (one each for UDMH fuel and N2O4 oxidizer) in the Progress docking collar for propellant transfer to corresponding connectors in the station collar. Three television cameras were carried near the docking unit.
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The tanker compartment carried two tanks each of UDMH and N2O4. Feoktistov stressed that these propellants were “chemically aggressive and poisonous to man.” To avoid spillage into the pressurized volumes of the station or the supply ship, fuel lines from the unpressurized tanker compartment ran along the exterior of the Progress orbital module, through the ducts in the docking collar, then into the unpressurized section containing the main propulsion system, which was located around the intermediate compartment at the aft end of the space station. The tanker compartment also carried tanks filled with nitrogen to serve as pressurant for the fuel system and to purge it of residual propellants. This prevented propellants from spilling on the docking apparatus and being accidentally introduced into the station.
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Control equipment normally located in the Soyuz orbital and descent modules was placed in the service module of the Progress spacecraft. The service module also carried equipment for controlling propellant transfer. Progress had mounted to its service module two infrared local vertical sensors (horizon sensors) and two ion sensors for its guidance system. Soyuz, by contrast, had one ion sensor and one infrared horizon sensor. Redundancy was provided because Progress was a wholly automated craft. The Progress service module was longer than the Soyuz module because of the extra equipment it carried.
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1.10.4 Progress Mission Descriptions
Dates are launch to reentry.

1.10.4.1 Progress Test Mission to Salyut 4
For information on Salyut operations during this Progress-related mission, see section 2.5.3.