Functional Cargo Block

[1][2] The FGB provides "functional" support in the form of electrical power, propulsion, guidance and docking; The support for "cargo" operations is supplied in the form of a pressurized habitable cargo storage section (accessible by the crew) and the externally mounted fuel tanks.

The Functional Cargo Block (FGB) was originally developed as support for the VA spacecraft – with both together forming the TKS spacecraft, intended for resupply flights to the Almaz space stations.

The TKS flights proved that the FGBs could form the basis of such a space station module, with the TKS being flight ready, and having a considerable larger capacity than the Progress – so the FGB and not the Progress became the basis of many Soviet and Russian space station modules.

[3] The basic layout of the exemplary Zarya FGB consists of two sections:[4] The PA is separated from the ICC by a spherical bulkhead containing an 800 mm hatch.

Both pressurized sections contain working and living areas, in addition to instrumentation separated by interior panels.

The ISS space station module Nauka is the latest space station module based on the Functional Cargo Block (FGB) design, attached with Prichal docking module as seen during VKD-51 spacewalk.