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49

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 ground and the backscatter is measured. The instrument ("Kaktus"), was developed in the early 60s. http://www.spacesafetymagazine.com/spaceflight/reentry-...


48

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 Station. The only other vehicle capable of carrying humans to the ISS, the Space Shuttle, was cancelled. That metric (no other vehicle can do it) will hopefully ...


46

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 Soyuz engines, of something like 115 m/s magnitude, is sufficient to lower the perigee of orbit into the uppermost part of the atmosphere. The orbital module and ...


42

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 because twelve days in zero g isn't enough time to take a significant toll on musculature, bones, and blood. The seventh returning astronaut, Daniel Tani, who you ...


39

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 - Со 60, Сs 137 isotopes). The receiver detects backscattering, reflected from the atoms inside the underlying surface. Gamma ray altimeters are used at low ...


36

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 hole. It takes a long time for hundreds of m3 to evacuate through a 2 mm hole.


35

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 computer systems, sometimes to components. I suspect you are reacting to an article like this one at SpaceflightNow.com which is actually a pretty good article. ...


33

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 "three feet"? As an aside, astronauts who have ridden the Soyuz home invariably describe it as a fairly wild ride. Terms I've personally heard include "car ...


31

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 era manned rockets that was used. The Russian launch escape system, SAS (Система Аварийного Спасения, or Sistema Avariynogo Spaseniya, meaning emergency ...


29

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 of the Orbiter had been detected, the shuttle crew would have had to hang out in the ISS until they could be rotated home using spare Soyuz capability. They ...


29

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, including the Apollo Command Module, have used this offset-mass approach to generate lift, thus achieving some measure of control over the atmospheric flight ...


27

There are usually 6 crew members, and 2 Soyuz spacecraft on station. Each Soyuz carries 3 astronauts. If there is an issue redocking during the move procedure, the backup plan is to return to earth. If they cannot redock and someone is left on the station, they would be stranded and cause all sorts of downstream issues. So no, you do not need 3 to move ...


26

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 so it precisely coincides with the launch site at precise time (thus the instantaneous launch window), which sometimes isn't possible. This Soyuz TMA-18M ...


26

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 helpful for position determination) as soon as the rocket was in motion. https://en.wikipedia.org/wiki/Inertial_platform Once operating, the platform's ...


25

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. The narrator in the video gives the height at which the retro-rockets fire as "70 cm": 70 cm above the ground, the six retro-rockets fire to ...


25

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 (about 6 m/s). That's your 3. That leaves about 7.5 km/s for part 2. The only remaining question is the split between 2a and 2b, ie the velocity when the ...


25

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 peroxide is passed over a heated catalyst, it decomposes to water and oxygen, and releases lots of energy, so the propellant goes from liquid to steam/gas, ...


24

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


23

There were more than 500 Zenit (including Vostoks and Voskhods) landing capsules; an order of 160 (as of today) manned and unmanned Soyuz variants. Plus prototypes used for modelling and testing on the ground. That's a pretty large number of used capsules. There are 65 pieces of equipment certified for reuse in Soyuz TMA landing module. Such as cosmonaut ...


22

It's really hard to answer this without complicating about how Soyuz spacecraft designers obviously didn't. Or crack a joke or two. It's a cramped little space vehicle and that space between the three crew, the seats they occupy and the control panels is pretty much all the space they have to crawl into it and later out of it. Moving the panels closer would ...


21

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 its bottom. The bottom module is the propulsion modules. The top module is the Utility module and has the washroom facilities and the airlock. They sleep in ...


21

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 module of the Soyuz TMA can only support up to three people. Since descent time is more or less constant regardless of the descent mode, and there's no way to ...


21

Most thrusters on the Soyuz-MS spacecraft use Nitrogen Tetroxide1 (N2O4, oxidizer) and Unsymmetrical Dimethylhydrazine2 (UDMH, fuel). These are stored (and burned) on the service module and both are fairly stable (from a storage-lifetime standpoint). For safety reasons it was decided that the descent module would use Hydrogen Peroxide3 (H2O2) ...


20

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 the cover before firing the SKD docked to Salyut-6 space station. This was a test burn. The cover was destroyed, and the engines left unprotected. As a ...


19

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 and time mechanisms operating according to their settings issue commands for sequential parachute deployment and for the execution of pre-landing ...


19

"Soyuz: A Universal Spacecraft" says the electrical system produces 23-34 volts. I saw a reference to a nominal 28VDC supply to the spacecraft in the Soyuz launcher manual; 28VDC is a global standard for aircraft power supplies. I think "906V" is a part number, not a voltage; the source for that section of the WP page says (my bolding): Finally, the ...


19

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 through that hole. I used this calculator with a pressure gradient of 101kPa (ISS standard) and 0.1 kPa through a 2mm hole and got a water flow rate of ~0.1 cubic ...


19

As Organic Marble points out, yes the US space program had G meters. They're likely to include these in future manned missions, as well. As for the true purpose of the toys: To humans, any sudden reduction in acceleration feels like falling. When the engines cut off, they are aware that there is less thrust, but the human body isn't great at telling you, ...


18

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 all the peroxide residuals are drained out."3 A secondary guidance, navigation and control system in the Descent Module enables the crew to maneuver the vehicle after the ...


16

Thanks to the paper linked by Jan Doggen in the comments we can say that it is a natural outcome of the shape of the parachute. In particular, the shape, together with the near absence of wind and the fact that the craft is descending near vertically determines that pulsating motion. In the words of the paper: The studies of [1, 2] demonstrated that ...


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