Diagram of re-entry for the Soyuz:
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http://spaceflight101.com/soyuz-tma-20m/wp-content/uploads/sites/77/2016/09/6618866_orig.jpg

Orbital Module:
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It houses all the equipment that will not be needed for reentry, such as experiments, cameras or cargo. The module also contains a toilet, docking avionics and communications gear. Internal volume is 6 m³, living space 5 m³. On the latest Soyuz versions (since Soyuz TM), a small window was introduced, providing the crew with a forward view.

Service Module:
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It has a pressurized container shaped like a bulging can that contains systems for temperature control, electric power supply, long-range radio communications, radio telemetry, and instruments for orientation and control. A non-pressurized part of the service module (Propulsion compartment, AO) contains the main engine and a liquid-fuelled propulsion system for maneuvering in orbit and initiating the descent back to Earth. The ship also has a system of low-thrust engines for orientation, attached to the Intermediate compartment. Outside the service module are the sensors for the orientation system and the solar array, which is oriented towards the sun by rotating the ship.


Consequences of bad jettisons:
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The services modules are jettisoned before the spacecraft hits the atmosphere. A failure or partial jettison of the modules means that the capsule will not enter the atmosphere heat shield first which can lead to a number of scenarios:
- Capsule pushed off course (by hundreds of km)
- High sustained g-loads on reentry
- Plasma on reentry can burn through the craft if the heat shield is not exposed and oriented properly resulting in loss of crew.

https://en.wikipedia.org/wiki/Soyuz_5
https://en.wikipedia.org/wiki/Soyuz_TMA-10
https://en.wikipedia.org/wiki/Soyuz_TMA-10

>> ^budzos:
Why? Mainly because I prefer not to drink microscopic bits of glass.


The force from the pressurized, jettisoned champagne is more than enough to prevent any glass bits from remaining in the bottle. This is a bad idea with non-pressurized beverages as the glass bits could stay inside.