57 votes
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Evacuating the ISS but wait, there's only one Spacecraft?

By design that will never happen. There are always enough return seats for the crew. This is exactly why the whole crew of one of the visiting vehicles gets in it whenever it undocks, even when it is ...
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50 votes
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Why were Space Shuttle astronauts able to walk off the orbiter?

Look at the STS-122 video. How many astronauts do you see? I see six. Seven astronauts landed with STS-122. The six you see were the crew of STS-122 who spent twelve days in space. They could walk ...
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50 votes
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Soyuz landing ground detection

Earlier Voskhod models used a retractable metal probe, but it was unreliable, especially in windy conditions. So in Soyuz, as the other answers have pointed out, a gamma-ray source is pointed at the ...
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49 votes
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Why do we only use Soyuz to send humans to the ISS?

Why do we only use Soyuz to send humans to the ISS? Because other than Chinese spacecraft (which aren't allowed), the Soyuz is currently the only one that can send humans to the International Space ...
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48 votes
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What eliminates the velocity when occupants return from ISS to earth, and how much?

Nearly all the velocity is cancelled by atmospheric deceleration of the descent module, before its parachutes are deployed. ISS orbital velocity is around 7700 m/s. An initial retro-burn of the ...
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40 votes

Soyuz landing ground detection

Soyuz uses gamma rays altimeter "Cactus", which starts soft landing engines just 1 meter before ground. Translation from russian wikipedia: The altimeter uses a source of gamma radiation (usually -...
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37 votes
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How could the 2018-08-30 Soyuz MS-09 / ISS leak be so slow?

The ISS is at 1 bar, i.e. 1 kgf/cm2, or 10 gramsf/mm2. So the pressure on that 2 mm hole is 31.4 gramsf, well within the range a human finger can handle. Also, the ISS is really big compared to the ...
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  • 122k
35 votes
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So with Soyuz being retired, what gets people up to the ISS and back down now?

Soyuz the booster and Soyuz the person carrying spacecraft are different. Soyuz the booster is based on the original R-7 ICBM and has seen a series of upgrades. Sometimes to engines, sometimes to ...
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  • 76.7k
34 votes
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Has the ISS ever not had a lifeboat?

It never actually happened, but there was a case when this situation had the potential for happening. That was the last shuttle flight, STS-135. If a critical flaw in the thermal protection system ...
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33 votes

Did the soft-landing rockets malfunction in the Soyuz (expedition 50 crew) landing?

The "three second" item is incorrect. In general (and this can be confirmed by watching multiple landings), the rockets fire approximately half a second before landing. Maybe they meant to say "...
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31 votes
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Was the LES used in the MS-10 abort?

Yes, the launch escape system was used, contrary to earlier reports based on assumptions and ignorance of Soyuz hardware. However, it was not the tower that we are familiar with on Mercury and Apollo ...
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  • 1,157
30 votes
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Soyuz Steering during Re-Entry

By itself the roll doesn't generate lift. But the Soyuz descent module (DM) enters with a non-axial center of mass that results in a non-zero angle of attack, and hence some lift. Several spacecraft, ...
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28 votes
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Can a single Soyuz return a crew of six back to Earth?

No. And it doesn't even matter that there's no space for a crew of six no matter how small they might be or if they threw away some other pieces and try to make do. The life support of the descent ...
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  • 75.6k
28 votes

Evacuating the ISS but wait, there's only one Spacecraft?

What would happen if there was a freak accident in which that the ISS needed to be evacuated and there was ONLY one space craft available? Carrying that to an even greater extreme, what would happen ...
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28 votes
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Where can I download the Soyuz Crew Operations Manual?

I can't recall where I got them from, so let me just re-host. Crew-ops manual Users manual
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26 votes
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Why did Soyuz TMA-18M take two days to reach the ISS?

Actually, a roughly 2-day rendezvous is standard*, and the 4-orbit expedited rendezvous, while being practiced more in the recent years, also involves phasing the International Space Station's orbit ...
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26 votes
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How did the attitude system of the uncrewed Soyuz 7K-OK No.1 fail on the launch pad in 1966, killing ground staff as LES was activated?

Rocket guidance systems generally use a fixed inertial platform based on gyroscopes to determine their orientation in space; an accelerometer solution would be useless to determine orientation (though ...
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26 votes

What eliminates the velocity when occupants return from ISS to earth, and how much?

The process is described here, which answers nearly all of your question. The reentry burn removes about 120 m/s of velocity from the capsule (that's your 1) and the final impact is 15 miles per hour ...
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26 votes

What are the reasons Soyuz's lifespan in orbit is limited?

Scott Manley answers this question here. Basically, it is due to the "shelf life" of the hydrogen peroxide propellant used by the attitude control thrusters of the Soyuz descent module. When hydrogen ...
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25 votes
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Did the soft-landing rockets malfunction in the Soyuz (expedition 50 crew) landing?

ESA has a nice 3-part video series on YouTube that explains on a high-level ascent, rendezvous, and re-entry. These are actual training videos that are shown to ESA astronauts during their training. ...
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25 votes
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Can a Soyuz-MS still propel itself back to earth if all its Hydrogen Peroxide decomposed?

Most thrusters on the Soyuz-MS spacecraft use Dinitrogen Tetroxide1 (N2O4, oxidizer) and Unsymmetrical Dimethylhydrazine2 (UDMH, fuel). These are stored (and burned) on the service module and both ...
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  • 1,951
24 votes
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August 30th 2018 Soyuz leak, any dangers for re-entry?

The leak is in the Orbital Module (OM), which is jettisoned prior to re-entry, so there is no concern there. Source: link in the question. Image source: spaceflight101.com
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21 votes
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Why does the Soyuz cover its main engine?

It's to protect the engine from the low temperature. The cover is removed before the deorbit burn: (Source: Kosmonavtika) $\rightarrow$ During mission Soyuz-32 in 1979, the cosmonauts forgot to open ...
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  • 4,853
21 votes
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How do astronauts and cosmonauts sleep on a Soyuz?

There are two modules in the Soyuz that are habitable. The Soyuz stack is three modules in total. The crew launches in the middle module, which is also where they land and has the heat shield on ...
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  • 76.7k
21 votes

Why doesn't Roscosmos launch Soyuz spacecraft with only Russians on board?

As of 24 April 2020, the Russians & Chinese are the only ones capable of sending people into orbit. The Chinese crewed space program is still in its early stages & only sends Chinese people ...
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  • 11k
20 votes

How could the 2018-08-30 Soyuz MS-09 / ISS leak be so slow?

This is the image of the hole (news source, although the image is from NASA) The hole is 2mm in diameter. Even with a total vacuum on the other side, you're not talking a lot of volume getting ...
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  • 6,810
19 votes

Can a single Soyuz return a crew of six back to Earth?

I found an actual reference for this, although it's in a memoir, not a technical book. Jerry Linenger's book Off The Planet states Unfortunately there is no way to squeeze more than three people ...
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19 votes
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Is this smoke from Expedition 53 returning Soyuz capsule?

It's a purge of remnant hydrogen peroxide from the "secondary control system".1 "On the “ОТСТРЕЛ ЛОБОВОЙ ТЕПЛОЗАЩИТЫ” (Bottom Shield Jettison) all УРМД thruster valves are opened and ...
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19 votes

Soyuz landing ground detection

Just to add a better source: From the Soyuz Crew Operations Manual The АКСП consists of barostatic and time mechanisms and the Гамма-лучевой высотомер (ГЛВ) (Gamma Ray Altimeter). The barostatic ...
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