Universal Docking Module
The Universal Docking Module (UDM) (Russian: Универсальный стыковочный модуль), was a planned Russian docking module for the International Space Station, to be jointly built by RKK Energia and Khrunichev. The Uzlovoy Module addition to the Nauka module, the eventual form of the FGB-2 design upon which the UDM was based, grew out of this proposal.
History
The original design resembled the Functional Cargo Block albeit larger, and would have it docked to the nadir (Earth-facing) Zvezda service module docking port, and have four docking ports to accommodate the two Russian Research Modules and the SO2 docking compartment.
Because one Research Modules was cancelled due to lack of funds, this module was also cancelled. The one remaining Research Module was then scheduled to be fitted to the open docking port on Zvezda. Later it was also cancelled and that port was allocated to the Docking Cargo Module. The DCM's scheduled location was later moved to Zarya, while the SO2 docking compartment was moved to the zenith docking port on Zvezda.
