As in the early days of Mir, the transfer compartment provides a suitable EVA airlock where spacewalkers in Orlan space suits removed a hatch after closing a few that connected the compartment to the rest of the station. The 'Transfer Compartment' attaches to the Zarya module, and has docking ports intended for the Science Power Platform (SPP) and the Universal Docking Module (UDM). Zvezda consists of the cylindrical 'Work Compartment' where the crews work and live (and which makes up the bulk of the module's volume), the small spherical 'Transfer Compartment' located at the front (with three docking ports), and at the aft end the cylindrical 'Transfer Chamber' (with one docking port) which is surrounded by the unpressurized 'Assembly Compartment' – this gives Zvezda four docking ports in total. Zvezda is around 1⁄ 4 the size of Polyus, and has no armaments. The Mir-2 space station was redesigned after the failure of the Polyus orbital weapons platform core module to reach orbit. The space frame was completed in February 1985 and major internal equipment was installed by October 1986. Its design lineage thus extends back to the original Salyut stations. It was in fact labeled as Mir-2 for quite some time in the factory. This means that Zvezda is similar in layout to the core module (DOS-7) of the Mir space station. The basic structural frame of Zvezda, known as 'DOS-8', was initially built in the mid-1980s to be the core of the Mir-2 space station.

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