Soyuz

The Soyuz family of spacecraft has its origins in the early russian space program. Because of its very flexible configuration of three modules, it got adapted to almost any task thinkable:

space station ferry
cargo transporter
lunar flyby spacecraft
manned earth observation spacecraft
unmanned earth observation satellite
orbital gamma ray telescope
test system for new docking systems
space station module

Configuration

Generally all soyuz spacecraft consist of:

Orbital module (BO)
Descend module (SA)
Service module (PAO)

Orbital module (OM, БО)

The orbital module contains the docking port, storage for food and water for the crew, storage for EVA space suits and a few spacecraft controls (mostly for light and communications initially). It has three hatches:

The ingress and EVA hatch. This is the only way of entering the spacecraft at launch,
The internal transfer hatch through the docking port (not installed in all soyuz crafts)
The hatch to the descend module.

Crew ingress takes place by the crew entering first the orbital module and then climb into the descend module. This is neccessary as the descend module is simply to small to allow more than three hatches.

Descend module (DM, СА)

The Descent Module contains the three crew couches that are used for launch and reentry, and storage cabinets under the couches for their spacesuits.

Propulsion module (PM, РАО)

The propulsion module consists of a intermediate section at the front, a pressurized electronics section and the unpressurized assembly section with the propulsion system, the electrical subsystem and parts of the life support system.

Directly behind the heatshield of the DM is the intermediate section, also known as transfer section, which contains the supports for the heatshield, most of the RCS thrusters and the smaller radiator of the thermal control system.

The electronics section contains the electronics used for docking and rendezvous, as well as the heat exchangers for the thermal control subsystem and the power supply systems. Most Soyuz variants rely on solar arrays as power supply, but for a long time, it was also common to use only batteries, which limited the independent flight time to about two days.

Behind the solar arrays is a large radiator which wrap around the whole module. The two radiators provide thermal control for the whole spacecraft until separation.

Variants

Soyuz A

Initial Soyuz concept for a lunar fly by spacecraft. Its mission consisted actually of three different spacecraft: Soyuz A as crew module, Soyuz B as eject stage and Soyuz C as tanker. The Soyuz A already had almost all typical design features of the later soyuz craft:

Three module configuration
Automatic rendezvous and docking system
Bell shaped reentry module
Vizor periscope
Probe and drogue docking system

It used solar cells for power supply. There are also some differences to the later built soyuz spacecraft:

Cylindrical orbital module, instead of the later spherical ones.
Ejectable electronics compartment at the aft of the spacecraft, which contained the rendezvous guidance system.
No internal transfer tunnel.

Soyuz P

Military version equipped with unguided rockets for attacking other spacecraft

Soyuz SE

Military spacestation, similar to the MOL. Its propulsion section was later included in the Almaz 1 station, as the prefered Almaz project was about to miss its deadline.

Soyuz 7K-OK (Soyuz 1 to Soyuz 9)

The first Soyuz generation, designed for docking test mission. Had no internal transfer tunnel, so crew transfer had to happen making a EVA.

Soyuz 7K-LOK

Lunar command module for the russian lunar landing program. Differed from other soyuz craft by many details.

Fuel cells for power supply
Kontakt rendezvous and docking system
Kontakt docking adapter
Orbital module with attitude control jets.
Larger propulsion system (called Block I)
Longer (10 cm) descend module with strengthened heatshield
Advanced control system, which formed the basis for the later Neptune control system of Soyuz T.

Soyuz 7K-OK (Soyuz 10 & 11)

Modified version of the first generation soyuz craft. Had an internal transfer tunnel for allowing the crew to enter a space station without EVA. The torus shaped electronics compartment on the earlier Soyuz craft got removed, with its contents being installed in the main electronics compartment in the service module. Still used the initial "Sirius" control system of the early Soyuz crafts, instead of the more advanced system installed in the Soyuz-LOK.

Soyuz 7K-T

After the soyuz 11 accidents, it became neccessary for the crew to wear pressure suits, reducing the crew to two astronauts because of the needed extra weight. Solar arrays got replaced by extra batteries, limiting the independend flight to only two days.

Soyuz 7K-ASTP

Modified soyuz 7K-T, with new solar cells and the APAS-74 androgynous docking systems. Used for the Apollo-Soyuz Test Project (ASTP).

Progress

Unmanned cargo and fuel transporter. Orbital module got modified to function as cargo carrier, and the descend module got replaced by a unpressurized fuel module. The docking port got modified to carry two extra connections for fuel and oxidizer. As the propellants (UDMH and N2O4) are very toxic and reactive, the propellant transfer lines run on the outside of the cargo module until the docking port.

Soyuz T

Improved the soyuz craft in many ways:

Solar cells (like used on the ASTP soyuz craft)
Unified propulsion system (RCS and main engine use the same propellant)
Digital onboard computer with 3x16KB ROM (Argon-16)
No backup engine for deorbit.
Again a crew of three, all wearing pressure suits
Greatly improved control system, called "Neptune", which included a CRT screen for help during docking and controls for the Argon-16.

Gamma

Gamma ray observatory, based on the progress spacecraft.

Soyuz TM

Modification of the Soyuz T:

Kurs rendezvous and docking system, allowing docking even with non-cooperative space stations.
Lighter parachutes
Improved main engine

Progress M

Improvement of the Progress spacecraft, for the Mir program. Carries the new Kurs guidance system and allowed the use of small Raduga reentry capsules to return experiments which have been to heavy for being returned in soyuz capsules.

Pirs

Docking module used on the ISS, based on a heavily modified soyuz spacecraft. only the service module remained the same, descend module and orbital module got replaced by the Docking Module. The Pirs module functions as extra airlock for EVAs and docking port for soyuz spacecraft.

Soyuz TMA

Final modification of the Soyuz family. Allowed greater or smaller astronauts as before, making it possible for space shuttle astronauts to use the Soyuz as reentry capsule in emergency. Also included an improved control system ("Saturn") with two VGA displays (one 16 color, the other amber). Used for the ISS.